BUILDING STRUCTURE

Field of the Invention

[01] The present invention generally relates to a modular construction system and a method for constructing a building structure using the modular construction system. The building structure can accommodate several functions like for instance temporary housing units, temporary office space, a workshop or atelier, a community centre, a pop-up store, a gallery or exhibition space, etc.

Backqround of the Invention

[02] In most cities the demand for affordable housing units is increasing. In particular, the demand for flats, apartments, duplex units and houses that can be rented temporarily on the social market by individuals or families with low or uncertain income, is growing fast. Although a lot of real estate like for instance office buildings or industrial buildings are empty and left unused while waiting for renovation or a new destination, the availability of affordable housing units for the growing social market is decreasing over time. The discrepancy between the growing demand for social housing units and the decreasing availability of such housing units in cities with vast amounts of real estate being left unused has inspired people to develop modular construction systems that allow to create temporary housing units. Such temporary housing units must accommodate a single person or a family and therefore be modular in terms of the amount of rooms and/or floors. Such housing unit further must provide basic comfort like electricity, water, heating, and preferably conforms with certain standards like locally applicable isolation norms and fire safety specifications.

[03] International patent application WO 2018/002433 A1 entitled "Box-Type Element" describes a modular construction system that consists of surface panels (1 - 4 in Fig. 1 ) interconnected through butterfly shaped tenons (11 in Fig. 3) that slide into dovetail shaped grooves (9 in Fig. 3) that extend along the entire height of the surface panels. The surface panels comprise at least three layers of lumber material glued on top of each other. The butterfly shaped tenons serve as keys locking panels, and may have other shapes as described in paragraph [0044]

[04] The modular construction system known from WO 2018/002433 A1 is limited in use and rather complex in production and mounting. The surface panels are rather large, covering for example an entire facade with multiple windows and/or doors. Such panels are difficult to transport, in particular inside existing buildings where stairways or elevators may have to be used to take a panel to an upper floor of the building that will be separated in social housing units. The tenons represent additional, non- structural parts that are difficult to mount as they must be lifted to a height above the panels before they can slide into the grooves. It is not clear from WO 2018/002433 A1 how closed housing units can be created, satisfying isolation and safety norms. It is also not clear from WO 2018/002433 A1 how basic supplies like electricity, water and heating can be ported to different rooms or even different floors of a temporary housing constructed using the panels and tenons.

[05] International patent application WO 2018/002432 A1 entitled "Method for Joining Box-Type Elements to Each Other" describes a similar modular construction system with same disadvantages.

[06] United States Patent Application US 2005/0050808 A1 entitled "Prefabricated Housing Structure" discloses another modular construction system consisting of wall panels and roof panels that enable to construct fully closed, temporary housing units. The wall panels have a complex structure with interlocking portions that facilitate connecting lateral edges of adjacent wall panels such that a rigid housing structure is formed with the need for tools.

[07] Although the modular system known from US 2005/0050808 A1 allows toolless configuration of housing units, the wall panels are complex to produce and connect. Fig. 8 of US 2005/0050808 A1 for instance shows the interlocking portions of the wall panels in detail. The complex, multi-facet interlocking portions require dedicated wall panel manufacturing machines. The resulting wall panels are not symmetric and consequently do not allow fast, dummy proof positioning and connecting during construction. The complex, multi-facet interlocking portions also do not allow to connect panels through a simple, sliding movement. To interconnect two panels, one panel must be lifted to a certain, predefined height relative to the other panel, the panel must be moved horizontally and thereafter a vertical, sliding movement allows engagement of the panels. It is not clear from US 2005/0050808 A1 how multi-floor housings can be created and/or how elementary supplies like electricity, water or heating can be provided.

[08] United States Patent US 10,221 ,568 B2 entitled "Integral Architectural Modular Assembly and Fabrication System with Interconnecting Universal Walls and Universal Connectors and Universal Roof Pieces" describes yet another modular construction system that consists of connecting parts. The system known from US 10,221 ,568 B2 comprises a ground ruler (7 in Fig. 8), wall panels (1 in Fig. 8) and vertical connectors (10 in Fig. 16) to interconnect the wall panels in a toolless manner. A vertical connector consists of a hollow connector element (10c in Fig. 13-14) and one or more C-shaped elements (10a in Fig. 13-14). The C-shaped elements (10a in Fig. 13-14) connect with the hollow connector element (10c in Fig. 13-14) through T-shaped rails (11 a in Fig. 13-14) that hook into complementary guides (11 in Fig. 13-14) mounted on each wall of the hollow connector element (10c in Fig. 13-14).

[09] The vertical connectors known from US 10,221 ,568 B2 rather loosely interconnect the wall panels. As mentioned in Col. 3, lines 18-21 , bolts are still required to bolt the C-shaped elements of the connector with the wall panel in order to secure the walls. Constructing a housing using the system of US 10,221 ,568 B2 hence requires mounting vertical connectors from hollow connector elements and C-shaped channels, and further involves bolting the vertical connectors and wall panels. The construction thus remains rather cumbersome and cannot be performed toolless.

[10] United States patent US 3,733,755 entitles "Bracket Standard and Base Rail System" describes a modular construction system that comprises ground rulers (20), wall panels (60, 70, 60a) and vertical columns (25, 26). A vertical column is made of two U-shaped parts (25, 26). The base of such U-shaped part (25, 26) is hollow with a bottom surface that is corrugated (31 , 32) to provide vertical rigidity and a top surface that contains a connector protrusion or slot (61 ) to receive a hook or bracket (63) that connects the wall panel (60, 70, 60a) to the vertical column. The hook or bracket (63) is screwed into the wall panel using screws (71 ). The internal space (48) of the U- shaped part (25, 26) provides space for wiring (50).

[11] Connecting wall panels to vertical columns in the system known from US 3,733,755 involves hooks or brackets (63) and screws (71 ), and therefore requires tools. If no screws are used, US 3,733,755 indicates that alternate fastening devices will be required (see col. 3, In. 48-53) hence requiring other fastening tools. Further, Fig. 4 of US 3,733,755 shows that the channel (48) is limited in size due to the complex structure of the U-shaped parts (25, 26). The channel (48) at best provides space for wiring (50), for instance electrical wiring, but will not accommodate water supply pipes, water drain pipes, heating pipes or sewage pipes, let aside a combination of such conduits. The complex structure of the U-shaped parts (25, 26), jointly forming a vertical column with cross-shaped intersection, also prevents the wall panels (60, 70, 60a) from having a substantially flat lateral surface, which further complicates the installation process. Actually, each wall panel is installed in three steps: firstly, a first wall element (60) is connected using brackets (63) and screws (71 ); secondly, a batt of insulating material (70) is installed against the first wall element (60); and thirdly, a second wall element (60a) is installed.

[12] Summarizing, existing modular construction systems rely on complex to manufacture parts, difficult to transport parts, and/or disadvantageous mounting using key elements, screws and bolts, or non-symmetric interlocking portions of panels.

[13] It is therefore an object of the present invention to disclose a modular construction system and corresponding construction method of a building structure that resolves one or more of the above-mentioned disadvantages of existing systems. More particularly, it is an object of the present invention to provide a modular construction system that consists of parts that are easy to manufacture, simple to transport through corridors, stairways and elevators, and that enable to rapidly mount and dismount a building structure that comprises one or plural floors, and one or plural rooms with all essential supplies (water, electricity, heating) and satisfying all applicable housing norms (heat isolation, acoustic isolation, fire safety). The modular construction system according to the invention preferably allows box-in-box construction such that empty real estate in cities can be turned for instance into temporary housing units for the social market.

Summary of the Invention

[14] According to a first aspect of the present invention, the above object is realized by a modular construction system based on interconnected parts as defined by claim 1 , the modular construction system comprising:

- at least one ground ruler, the ground ruler having a front side, back side, bottom surface, top surface and lateral sides, wherein the top surface comprises a cut-out adapted to receive a part;

- at least one wall panel, each wall panel of the at least one wall panel having a front side, back side, bottom surface, top surface and lateral sides, wherein each lateral side comprises at least two swallowtail connector protrusions; and

- at least one vertical column, each vertical column of the at least one vertical column comprising parts glued together to create a vertical channel for conduits, and having at least one lateral side comprising two swallowtail connector notches adapted to receive the swallowtail connector protrusions of the wall panel.

[15] Thus, the invention resides in a modular construction system of parts that allow to build modular building structures having one or plural rooms. The building structure can accommodate several functions like for instance temporary housing units, temporary office space, a workshop or atelier, a community centre, a pop-up store, a gallery or exhibition space, etc. The parts at least comprise a ground ruler with cut-out in its top surface, enabling to vertically position structural elements like wall panels or vertical columns and/or enabling to position other ground structure elements like ground joists. The parts may comprise plural ground rulers having different lengths and/or having different cut-out positions. The ground rulers allow to lay a floor plan for the building structure. The parts further comprise a wall panel, having a bottom surface that engages with the ground ruler, a front side facing outward the building structure, a back side facing inward the building structure, a top surface, and two lateral sides. Preferably, the front side and back side are identical, resulting in a symmetric wall panel that can be placed in a dummy-proof manner by technicians mounting the building structure. The parts may comprise plural wall panels like for instance a basic wall panel, a window wall panel, a door wall panel. These wall panels preferably have uniform dimensions to simplify installation of the building structure and to allow easy adaptation of the building structure over time, like for instance replacement of a basic wall panel by a window wall panel. Each of the wall panels has at least two swallowtail connector protrusions on its lateral sides. These swallowtail protrusions simplify the mounting and dismounting of temporary building structures as will be explained further below, and they considerably contribute to reducing the time required to mount a building structure. A first swallowtail connector protrusion allows to connect the wall panel to another structural element, for example a vertical column, whereas the second swallowtail connector protrusion allows to align and fix the wall panel. The presence of swallowtail connector protrusions on both lateral sides of the wall panel further contributes to the symmetry of the wall panel, allowing dummy-proof installation by technicians mounting the building structure. The parts further also comprise a vertical column, i.e. a structural element that comprises two U-shaped elements, the leg ends of which are glued together to form a vertical column with central, vertical opening or channel. Alternatively, the vertical channel may be formed by gluing other parts, like for instance two solid wall elements, made of wood and forming lateral sides of the vertical column, glued together by two multiplex plates forming the front and back surfaces of the vertical column. The vertical channel allows conduits of various nature like for instance electrical conduits or water supply conduits to extend vertically, allowing for instance to take basic supplies to the ceiling or to upper floors in a multi floor building structure. The vertical column further may have a bottom surface designed to engage with a cut-out in the top surface of the ground ruler. The vertical column further has at least one lateral side comprising two swallowtail connector notches positioned at respective heights and having respective shapes and dimensions allowing the vertical column to receive the swallowtail connector protrusions of a wall panel. The parts may comprise plural vertical columns like for instance a vertical column having swallowtail connector notches at two opposite lateral sides, a vertical column having swallowtail connector notches at only one lateral side, a vertical column having swallowtail connector notches at two lateral sides and a backside (using a T-shaping part as will be described below), and/or a vertical column having swallowtail connector notches at one lateral side and a back side (using again a T-shaping part). This way, the vertical columns can serve as structural connector element between two wall panels, structural element terminating a standalone wall, structural corner element interconnecting two wall panels under an angle of 90 degrees, and/or structural T-element interconnecting three wall panels. The swallowtail connectors between wall panels and vertical columns allow toolless mounting of the building structure, with limited effort by technicians who can easily transport the universal wall panels, ground rulers and vertical columns through corridors, stairways and elevators. In addition, the vertical columns serve as vertical channel enabling to extend conduits to the ceiling and/or upper floors of a building structure. Fast and dummy-proof construction of modular building structures using the modular construction system according to the invention allows to turn temporary empty or unused buildings in cities into affordable and comfortable housing spaces for the social market, having one or plural rooms on one or plural floors.

[16] In embodiments of the modular construction system according to the invention, as defined by claim 2, the vertical column comprises two U-shaped parts the leg ends of which are glued together to create the vertical channel, and the vertical column has a bottom surface adapted to engage with the cut-out in the ground ruler.

[17] Indeed, as explained here above, one way to create the vertical channel for conduits consists of gluing together the respective leg ends of two U-shaped elements. This way, a solid vertical column with load-bearing capacity and central, vertical opening or channel is created using two identical U-shaped elements.

[18] In embodiments of the modular construction system according to the invention, as defined by claim 3, the at least one vertical column comprise:

- a first vertical column having only one lateral side comprising the two swallowtail connector notches;

- a second vertical column having two lateral sides each comprising the two swallowtail connector notches;

- a third vertical column comprising the first vertical column and a T-shaping part, the T-shaping part having a first lateral side glued to a back side of the vertical channel created by the first vertical column, and having a second lateral side comprising two swallowtail connector notches adapted to receive the swallowtail connector protrusions of the wall panel; - a fourth vertical column comprising the second vertical column and a T-shaping part, the T-shaping part having a first lateral side glued to a back side of the vertical channel created by the second vertical column, and having a second lateral side comprising two swallowtail connector notches adapted to receive the swallowtail connector protrusions of the wall panel; and

- a fifth vertical column comprising the second vertical column, a first T-shaping part, the first T-shaping part having a first lateral side glued to a back side of the vertical channel created by the second vertical column, and having a second lateral side comprising two swallowtail connector notches adapted to receive the swallowtail connector protrusions of the wall panel, and a second T-shaping part, the second T- shaping part having a first lateral side glued to a back side of the vertical channel created by the second vertical column, and having a second lateral side comprising two swallowtail connector notches adapted to receive the swallowtail connector protrusions of the wall panel.

[19] Thus, the vertical column may exist in five different variants. In the first variant, two swallowtail connector notches are foreseen in one lateral side of the vertical column. The opposite lateral side in other words remains a flat surface over its entire length, without swallowtail protrusions. This first variant of the vertical column can connect to a single wall panel and therefore can be used as structural element ending a standalone wall. Such standalone wall may for example be desired to separate a large open space inside the building structure into smaller spaces without creating separate rooms, or may be used as a fence or facade extension outside the building structure. This first variant of the vertical column shall be named an end column throughout this patent application. In the second variant, two swallowtail connector notches are foreseen in one lateral side, and two additional swallowtail connector notches are foreseen in the opposite lateral side. This second variant of the vertical column can interconnect two wall panels that are located in a same plane and thus form part of a same wall, for example two basic wall panels, a basic wall panel and a window wall panel, etc. This second variant of the vertical column shall be named a connector column throughout this patent application. In the third variant of the vertical column, two swallowtail connector notches are foreseen in one lateral side, and two additional swallowtail connector notches are foreseen in the back side. This is made possible by gluing a T-shaping part onto the backside of the first variant of the vertical column. The T-shaping part is foreseen with the additional two swallowtail connector notches. This third variant of the vertical column allows to interconnect two wall panels that are positioned under an angle of 90 degrees and therefore form part of different walls of the building structure. This third variant of the vertical column shall be named a corner column throughout this patent application. In the fourth variant of the vertical column, two swallowtail connector notches are foreseen in one lateral side, two additional swallowtail connector notches are foreseen in the opposite lateral side, and two further swallowtail connector notches are foreseen in the back side. This is made possible by gluing a T-shaping part onto the backside of the second variant of the vertical column. The T-shaping part is foreseen with the further two swallowtail connector notches. This fourth variant of the vertical column allows to interconnect 3 wall panels, one of which is positioned under an angle of 90 degrees vis-a-vis the other two panels. This fourth variant of the vertical column shall be named a T-column throughout this patent application, and is useful to create inner walls inside the building structure, extending from an external wall of the building structure or extending from another inner wall of the building structure. In the fifth variant of the vertical column, two swallowtail connector notches are foreseen in one lateral side, two additional swallowtail connector notches are foreseen in the opposite lateral side, two further swallowtail connector notches are foreseen in the back side, and another two swallowtail connector notches are foreseen in the front side. This is made possible by gluing a T-shaping part onto the backside of the second variant of the vertical column and gluing a second T-shaping part onto the frontside of the second variant of the vertical column. The first and second T-shaping parts are each foreseen with two further swallowtail connector notches. This fifth variant of the vertical column allows to interconnect 4 wall panels, two of which are positioned under an angle of 90 degrees vis-a-vis the other two panels. This fifth variant of the vertical column shall be named a cross-column throughout this patent application, and is useful to create inner walls inside the building structure, extending from an external wall of the building structure or extending from another inner wall of the building structure. The T-column in other words is essential in order to enable the construction of the multi-room building structures.

[20] In embodiments of the modular construction system according to the invention, as defined by claim 4, the two swallowtail connector notches comprise a first, smaller notch near a top end of the vertical column and a second, wider notch near a bottom end of the vertical column.

[21 ] Correspondingly, in embodiments of the modular construction system according to the invention, as defined by claim 5, the two swallowtail connector protrusions comprise a first, smaller protrusion near a top end of said wall panel and a second, wider protrusion near a bottom end of said wall panel.

[22] The first, smaller swallowtail connector notch at the top end of the vertical column is used to connect a wall panel to the vertical column. Thereto, the wall panel is first lifted slightly and made hanging on top of the vertical column by letting the corresponding smaller swallowtail connector protrusion of the wall panel rest on the top surface of the vertical column. Thereafter, the smaller swallowtail connector protrusion is moved and released into the smaller swallowtail connector notch of the vertical column resulting in an engaging connection between the wall panel and vertical column. The second, larger swallowtail connector notch near the bottom end of the vertical column is used to align and fix the wall panel. When releasing the wall panel from its hanging position to its connected position, the second, larger swallowtail connector protrusion of the wall panel is moved into the second, larger swallowtail connector notch of the vertical column. This way, the wall panel becomes aligned with the vertical column and fixed over its entire height such that it cannot swing.

[23] In embodiments of the modular construction system according to the invention, as defined by claim 6, the at least one wall panel comprise:

- a basic wall panel without any saving;

- a window wall panel comprising a window saving;

- a door wall panel comprising a door saving;

- a large window panel.

[24] The modular construction system hence preferably comprises amongst its parts a plurality of wall panels. These wall panels preferably have the same, uniform dimensions and all of them have the two swallowtail connector protrusions at both lateral sides. The different wall panels however may have different functions. A basic wall panel without any savings for instance serves to create a blind wall external to or internal to a building structure. A window wall panel comprising a window saving allows to create external windows, or internal rooms or spaces interconnected through an opening in the wall. Multiple window wall panels may form part of the modular construction system of for instance building structures having windows with varying sizes are constructed. A door wall panel comprises a door saving, i.e. a saving reaching upwards from the bottom surface of the wall panel, and allows to create external and internal doors for a building structure. In embodiments where the wall panels do not have equal widths, larger wall panels preferably have the width of n times a basic wall panel plus (n-1 ) times the width of a column, n being an integer value. This way, the larger wall panel takes the same place as n wall panels with intermittent columns. For instance, a large window panel may have the width of 2 normal window panels plus the width of a single vertical column. The large window panel may be used to create a larger window or larger opening in a building structure without jeopardizing the periodicity or regularity in the pattern of wall panels and vertical columns that simplifies the construction of the building structure according to the invention.

[25] In embodiments of the modular construction system according to the invention, as defined by claim 7, the wall panel comprises a horizontal channel extending between its lateral sides at a first predetermined height.

[26] The horizontal channel extending between opposite lateral sides of the wall panel at a first predetermined height allows to pull conduits of various nature through walls. The horizontal channel may have a circular, rectangular or square intersection and may have a size accommodating electrical conduits, water supply pipes, discharge pipes, etc. The provision of such horizontal channel at a first predetermined height allows to pass conduits through multiple wall panels, and allows flexible provision of various functions like a power supply, an electrical switch, a water tap, a sink, a toilet, a shower, a heating, etc., anywhere in the building structure. Such a function can be mounted against a wall panel at any location according to the inhabitants' preferences, and can then be connected at the first predetermined height to the necessary conduits that pass through the wall panel.

[27] In embodiments of the modular construction system according to the invention, as defined by claim 8, the vertical column comprises a horizontal channel extending between a lateral side or back side and the vertical channel at the first predetermined height.

[28] Indeed, in order to enable passing conduits from one wall element to a neighbouring wall element, also the vertical columns must be provided with horizontal channels at the first predetermined height. These horizontal channels are established by horizontal holes interconnecting the central vertical channel that always forms part of a vertical column with lateral sides of the vertical column (in case of a connector column), horizontal holes interconnecting the central vertical channel of the vertical column with a lateral side and back side (in case of a corner column), or horizontal holes interconnecting the central vertical channel of the vertical column with as well the lateral sides as the backside (in case of a T-column) and the frontside (in case of a cross-column).

[29] Embodiments of the modular construction system according to the invention, as defined by claim 9, further comprise:

- at least one ceiling ruler, each ceiling ruler of the at least one ceiling ruler having a front side, back side, bottom surface, top surface and lateral sides, wherein the bottom surface is designed to engage with a top surface of the wall panel.

[30] In order to be able to mount a ceiling, a ceiling ruler is placed on top of the wall panels. The parts may comprise plural ceiling rulers having different lengths. Each ceiling ruler preferably has a bottom surface that is designed in shape and size to fit onto a recess provided in the top surface of the wall panels.

[31] Embodiments of the modular construction system according to the invention, as defined by claim 10, further comprise:

- at least one ceiling panel; and

- at least one ceiling joist.

[32] Thus, the ceiling of a building structure is made of a flat ceiling panel that is lying on top of the ceiling rulers. Thereon, at regular distances, ceiling joist are provided that give structure to the ceiling or roof and prevent the ceiling or roof to sag or collapse. [33] In embodiments of the modular construction system according to the invention, the ceiling joist has a beam shape.

[34] Beam shaped joists are easy to manufacture.

[35] In alternative embodiments of the modular construction system according to the invention, the ceiling joist has an l-shape.

[36] l-shaped joists are lighter in weight than beam shaped joists and further bring the advantage of being easier to handle and transport.

[37] Embodiments of the modular construction system according to the invention, as defined by claim 11 , further comprise:

- at least one ceiling strip adapted to be placed between the ceiling panel and said ceiling joist.

[38] The ceiling strip serves as a positioning element, indicating where the ceiling joist must be placed.

[39] In embodiments of the modular construction system according to the invention, as defined by claim 12, the wall panel comprises:

- a first sheet establishing the front side;

- a second sheet establishing the back side;

- a wooden frame in between the first sheet and the second sheet, establishing the lateral sides, the top surface and the bottom surface; and

- a rock wool insulation panel in the space surrounded by the first sheet, the second sheet and the wooden frame.

[40] The wall panels preferably are made to satisfy acoustic isolation norms, heath isolation norms and fire safety specifications, while being rigid but lightweight for transport reasons. This may be achieved by a wall panel that consists of four elements: a front side sheet made for instance of fire resistant multiplex material, a rectangular frame made of wood or laminated wood (like for instance Kerto) with a preferred thickness of 45 millimetres constituting the lateral sides, bottom surface and top surface of the panel, a back side sheet made for instance of fire resistant multiplex material, and a rock wool insulating panel filling the space in between the front side panel, rectangular frame and back side panel. The rockwool insulating panel provides resistance to temperatures up to 1000 °C and does not pass toxic gasses in case of fire.

[41] In embodiments of the modular construction system according to the invention, the wall panel further comprises:

- a vapour barrier in the space surrounded by the first sheet, the second sheet and the wooden frame.

[42] Indeed, in between the front side panel and rock wool insulation, a vapour barrier may be provided. Likewise, in between the back side panel and rock wool insulation, a vapour barrier may be provided or a second vapour barrier may be provided when combined with the vapour barrier between the front side panel and rock wool insulation. The vapour barrier has to be fixed with screws or nails and therefore introduces complexity in the production process. When the front side panel and/or the back side panel are vapour proof, an additional vapour barrier may be superfluous and left out, simplifying the production of wall panels.

[43] In embodiments of the modular construction system according to the present invention, as defined by claim 13, the ground ruler further comprises a ground ruler element having a milling line in its top surface, and/or having one or more circular cut outs for receiving a pin from a vertical column and/or receiving one or more pin from a wall panel.

[44] The milling line, preferably provided over the entire length of the ground ruler element, provides space for air-tightening material like a rubber strip, a swelling band or other isolation material that improves the airtightness of the building structure. The circular cut-outs in the top surface of the ground ruler element are shaped and dimensioned to receive pins that provide stability to vertical parts placed on the ground ruler element. A circular cut-out may for instance be provided to receive a pin attached to the bottom surface of a vertical column, for instance a corner column. Other circular cut-outs may for instance be provided to receive pins attached to the bottom surface of wall panels. As an example, the bottom surfaces of door jambs of a door wall panel may for instance be provided with pins that engage with circular cut-outs in the top surface of a ground ruler element to provide stability to the door wall panel.

[45] In embodiments of the modular construction system according to the invention, as defined by claim 14, a vertical column further has a milling line in its lateral surface.

[46] This way, also the airtightness of vertical gaps in between columns and wall elements is improved. The milling line in one or more lateral surfaces of a vertical column preferably extends over the entire height of the vertical column and is shaped and dimensioned to provide space for air-tightening material like a rubber strip, a swelling band or other isolation material that improves the airtightness of the building structure. In preferred embodiments, the milling line provided in the top surface of ground rulers is shaped and dimensioned identically to the milling line provided in lateral sides of the vertical columns, such that the same strip, band or isolation material can be used to air-tighten horizontal gaps between the ground ruler and wall panels and vertical gaps between the vertical columns and wall panels.

[47] In embodiments of the modular construction system according to the invention, as defined by claim 15, a wall panel has pins extending downward from its bottom surface to engage with holes in the top surface of a ground ruler element.

[48] Two downward extending pins are particularly useful in order to realize a stable and rigid connection between a door wall panel and the ground ruler. Each door jamb thereto is provided with a downward extending pin at its bottom surface that fits into a hole provided in the top surface of a ground ruler element. Also other wall panels may be provided with one or plural downward extending pins that fit into holes provided in the top surface of ground ruler elements. Such holes are preferably provided at regular distance from each other and have constant relative positions vis-a-vis the wall panels that are placed on the ground ruler elements.

[49] In embodiments of the modular construction system according to the invention, as defined by claim 16, the vertical column has a pin extending downward from its bottom surface to engage with a hole in the top surface of a ground ruler element. [50] Indeed, just like wall panels also vertical columns can be provided with a pin that engages with a cut-out in the top surface of a ground ruler element to obtain a more stable and more rigid connection. In particular for corner vertical columns, such improved stability through a pin at its bottom surface engaging with a circular hole in the top surface of a ground ruler element is preferred.

[51] According to a second aspect of the present invention, the above object is realized by a method for constructing a building structure as defined by claim 17, the method comprising the steps of:

A. laying a floor plan using ground rulers, the ground ruler having a top surface with at least one cut-out adapted to receive a part;

B. placing a first vertical column, the vertical column comprising parts glued together to create a vertical channel for conduits, and having lateral sides at least one of which comprises two swallowtail connector notches;

C. hanging a wall panel onto the first vertical column, the wall panel having a front side, back side, bottom surface, top surface and lateral sides each comprising two swallowtail connector protrusions, said hanging of the wall panel resulting in one of the swallowtail connector protrusions resting on a top surface of the first vertical column;

D. placing a second vertical column against the wall panel, the second vertical column comprising parts glued together to create a vertical channel for conduits, and having lateral sides at least one of which comprises two swallowtail connector notches, the placing of the second vertical column resulting in one of the swallowtail connector protrusions of the wall panel resting on a top surface of the second vertical column;

E. releasing the wall panel such that the swallowtail connector protrusions at a first lateral side of the wall panel engage with the swallowtail connector notches of the first column and the swallowtail connector protrusions at a second lateral side of the wall panel engage with the swallowtail connector notches of the second column;

F. repeating the steps D and E to create additional walls of the housing, wherein the second vertical column becomes the first vertical column in a next iteration of the steps.

[52] Thus, according to a second aspect, the present invention foresees in a dummy- proof and toolless method for mounting a building structure from universal parts comprising a ground ruler, wall panels and vertical columns, wherein no nails, screws or bolts are used. The universal parts are compact and lightweight, and therefore easy to transport through corridors, stairways and elevators such that the construction method according to the invention can be used to mount building structures also at empty or unused upper floors of office buildings in cities. Constructing a building structure starts with laying the ground plan using ground rulers. The ground rulers preferably have a fixed, predetermined length or a limited number of fixed, predetermined lengths. The ground rulers also have cut-outs in their top surfaces enabling to position and hold other parts like a vertical column, a wall panel, joists, etc. In an embodiment, the ground rulers are placed such that a cut-out is located at corners. Further cut-outs are located equidistantly from each other, the distance between two subsequent cut-outs being equal to the width of a wall panel. A first vertical column is then placed on a first cut-out of a ground ruler. Preferably, the first vertical column is a corner column and the first cut-out is located at a corner in the ground plan. The first vertical column has a central vertical channel and swallowtail connector notches in at least one lateral side. Following placement of the first vertical column, a wall panel is hung in position. The wall panel, i.e. either a basic wall panel, window wall panel or door wall panel having a width equal to the distance between two ground ruler cut-outs, is lifted slightly by one or two technicians and moved such that a swallowtail connector protrusion near the top end of a lateral side rests on the top surface of the already placed first vertical column. The wall panel is kept hanging in this position while a second vertical column is being placed. The second vertical column, for instance a connector column is placed on the next ground ruler cut-out and the hanging wall panel is moved such that the swallowtail connector protrusion at the top end of its second lateral side is resting on the top surface of the second vertical column. Also the second vertical column has a central vertical channel obtained by gluing together two U-shaped parts that jointly form the connector column. As an alternative, the vertical channel may be formed by gluing other parts, like for instance two solid wall elements, made of wood and forming lateral sides of the vertical column, glued together by two multiplex plates forming the front and back surfaces of the vertical column. In the next step, the hanging wall panel is released. Thereto, the hanging wall panel is moved forwardly or backwardly until its top swallowtail connector protrusions slide into the top swallowtail connector notches of the first and second vertical columns. Care is taken that at the same time the lower swallowtail connector protrusions of the first wall panel slide into the lower swallowtail connector notches of the first and second columns. This way, the first wall panel aligns and fixedly engages with the first and second vertical columns. The steps of hanging a wall panel, placing an additional vertical column and releasing the wall panel to engage with the vertical columns is repeated wherein the already placed second vertical column of a previous iteration becomes the first vertical column in a next iteration. The selection of the type of vertical column (end, corner, connector, T, cross) and the selection of the type of wall panel (basic, window, door) depends on the housing plan. By iteratively repeating the above described toolless steps, the entire modular building structure can be construed in no time. A four room apartment for instance can be mounted in 5 days. This is possible in open air on unused lots of ground, but also on unused floors of buildings whereon the building structures can be construed as temporary box-in-box units that can be rented at affordable prices solving the problem of a growing demand for affordable housing in cities with many industrial or office buildings being left empty or unused at least temporarily.

[53] In embodiments of the method for constructing a building structure according to the invention, as defined by claim 18, a corner style is created by using a first vertical column or second vertical column further comprising a T-shaping part, the T-shaping part having a first lateral side glued to a back side of the vertical channel created by the second vertical column, and having a second lateral side comprising two swallowtail connector notches.

[54] Indeed, in order to create a corner style, a particular type of vertical column must be used. Such vertical column, named corner column, still comprises parts glued together to form a central vertical channel. One of the parts has two swallowtail connector notches in the surface that constitutes a lateral side of the vertical column. In addition, a T-shaping part must be glued onto the back side of the vertical column. The T-shaped part has two additional swallowtail connector notches in its lateral side opposing the side that is glued to the vertical column. This lateral side having the additional swallowtail connector notches shall constitute the new backside of the vertical column. The so created corner column has a pair of swallowtail connector notches on a lateral side and a pair of swallowtail connector notches on its backside, allowing to interconnect two wall panels that are placed under an angle of 90 degrees vis-a-vis each other.

[55] In embodiments of the method for constructing a building structure according to the present invention, as defined by claim 19, internal walling is made possible by using a first vertical column or second vertical column having two lateral sides each comprising two swallowtail connector notches and further comprising one or two T- shaping parts, the T-shaping parts having a first lateral side glued to a back side or front side of the vertical channel created by the first or second vertical column, and having a second lateral side comprising two swallowtail connector notches.

[56] Thus, also to create an internal wall starting for instance from external walling, a particular type of vertical column must be used. Such vertical column, named T- column or cross-column, still comprises parts glued together to form a central vertical channel. These parts have two swallowtail connector notches in the surfaces that constitute the lateral sides of the vertical column. In addition, a T-shaping part must be glued onto the back side of the vertical column and/or a T-shaping part may be glued onto the front side of the vertical column. The T-shaped part has two additional swallowtail connector notches in its lateral side opposing the side that is glued to the vertical column. This lateral side having the additional swallowtail connector notches shall constitute the new backside and/or frontside of the vertical column. The so created T-column or cross-column has a pair of swallowtail connector notches on each lateral side and a pair of swallowtail connector notches on its backside and/or frontside, allowing to interconnect three wall panels one of which (the internal wall) is placed under an angle of 90 degrees vis-a-vis the other two (either external walls or internal walls), or allowing to interconnect four wall panels under angles of 90 degrees.

[57] Embodiments of the method for constructing a building structure according to the invention, as defined by claim 20, further comprise the steps of:

- placing at least one ceiling ruler on top of the wall panel, each ceiling ruler of the at least one ceiling ruler having a front side, back side, bottom surface, top surface and lateral sides, wherein the bottom surface is designed to engage with a top surface of the wall panel;

- placing at least one ceiling panel on top of the ceiling ruler; and - placing at least one ceiling joist on top of the ceiling panel.

[58] In order to provide the building structure with a ceiling, the method foresees in placing ceiling rulers on top of the vertical wall elements, laying flat ceiling panels on top of the ceiling rulers, and placing at regular distances of each other ceiling joist - either beam shaped or l-shaped - on top of the ceiling panels to span the ceiling. Such ceiling can then serve as base for the floor of an additional floor.

[59] In embodiments of the method for constructing a building structure according to the present invention, as defined by claim 21 , the steps A-F are repeated to establish additional floors in the building structure.

[60] Indeed, the above described method allows to build additional floors such that a multi-level apartment is created. Thereto, a flooring must be provided on top of the ceiling of a lower layer. The flooring can be realised by using the ceiling parts in the reverse order. On top of such flooring, ground rules can be used to lay out the ground plan of the upper floor. Thereafter, vertical columns and wall panels can be used to construct the upper floor in a fast and toolless manner.

[61] Embodiments of the method for constructing a building structure according to the present invention, as defined by claim 22, further comprise the steps of:

- providing connections through horizontal channels extending at a first predetermined height through the wall panel between lateral sides thereof, and through horizontal channels extending at the first predetermined height through the vertical column between a lateral side, front side or back side thereof and the vertical channel thereof.

[62] In embodiments of the invention wherein the wall panels and vertical columns are provided with horizontal channels at a first predetermined height, connections of various nature, like for instance electrical power supply connections and water supply conduits are extended through these channels to enter the different rooms of the building structure. [63] Embodiments of the method for constructing a building structure according to the present invention, as defined by claim 23, further comprise the steps of:

- providing connections through the vertical channel of the vertical column.

[64] When a multi-level building structure, like a duplex or multi-floor apartment is constructed, the central vertical channel in one or several vertical columns can be used to extend certain connections, like power supply connections and water supply conduits, to the upper floor of the building structure.

Brief Description of the Drawinqs

[65] Fig. 1 illustrates an embodiment of a building structure 100 constructed using an embodiment of the modular construction system according to the present invention;

[66] Fig. 2 illustrates a ground ruler 101 that forms part of an embodiment of the modular construction system according to the present invention;

[67] Fig. 3A-3C illustrate wall panels 110, 111 , 112 that form part of an embodiment of the modular construction system according to the present invention;

[68] Fig. 3D represents an exploded view of a wall panel 110 that forms part of an embodiment of the modular construction system according to the present invention;

[69] Fig. 4 illustrates a first vertical column 120 that forms part of an embodiment of the modular construction system according to the present invention;

[70] Fig. 4A-4B illustrate U-shaped parts 401 , 402 used to create the vertical column

120 of Fig. 4;

[71] Fig. 5 illustrates a second vertical column 121 that forms part of an embodiment of the modular construction system according to the present invention;

[72] Fig. 5A-5B illustrate U-shaped parts 501 , 502 used to create the vertical column [73] Fig. 6 represents a top view of a vertical column 120 that forms part of an embodiment of the modular construction system according to the present invention;

[74] Fig. 7A-7B show in more detail swallowtail connector notches in a vertical column that forms part of an embodiment of the modular construction system according to the present invention;

[75] Fig. 8 illustrates a T-shaping part 800 used to create vertical columns that form part of an embodiment of the modular construction system according to the present invention;

[76] Fig. 9A-9E illustrate variant vertical columns 901-905 that form part of an embodiment of the modular construction system according to the present invention;

[77] Fig. 10 illustrates a ceiling ruler 130 that forms part of an embodiment of the modular construction system according to the present invention;

[78] Fig. 11 illustrates a ceiling border beam 132 that forms part of an embodiment of the modular construction system according to the present invention;

[79] Fig. 12 illustrates a ceiling strip 134 that forms part of an embodiment of the modular construction system according to the present invention;

[80] Fig. 13A and Fig. 13B illustrate ceiling joists 133 and 135 that form part of respective embodiments of the modular construction system according to the present invention;

[81] Fig. 14A-14I illustrate subsequent steps in embodiments of the method for constructing a building structure according to the present invention;

[82] Fig. 15A and Fig 15B respectively illustrate ground ruler elements 1500, 1550, 1510, 1560 and a ground structure that form part of a second embodiment of the modular construction system according to the present invention; [83] Fig. 16A-16D illustrate wall panels 1600, 1610, 1620, 1630 that form part of the second embodiment of the modular construction system according to the present invention;

[84] Fig. 17A-17E illustrates a first vertical column 1700 that forms part of the second embodiment of the modular construction system according to the present invention;

[85] Fig. 18A-18D illustrate variant vertical columns 1700, 1800, 1810, 1820 that forms part of the second embodiment of the modular construction system according to the present invention;

[86] Fig. 19 illustrates ceiling ruler elements 1900, 1950 that form part of the second embodiment of the modular construction system according to the present invention;

[87] Fig. 20 illustrates a ceiling joist 2000 that forms part of the second embodiment of the modular construction system according to the present invention;

[88] Fig. 21 illustrates a ceiling structure 2100 that forms part of the second embodiment of the modular construction system according to the present invention; and

[89] Fig. 22A-22F illustrate subsequent steps in a second embodiment of the method for constructing a building structure according to the present invention.

Detailed Description of Embodiment(s)

[90] Fig. 1 shows a building structure 100 constructed using parts of an embodiment of the modular construction system according to the present invention. The building structure 100 is built by technicians executing an embodiment of the construction method according to the invention. The building structure 100 is made of ground rulers 101 and various wall panels 110,111 , 112. The wall panels 110, 111 , 112 are kept in position by vertical columns 120, 121 that serve as structural elements at corner styles and between neighbouring wall panels. Preferably, the wall panels have a universal width and height, for example 122 cm by 244 cm. Also the vertical columns 120, 121 preferably have a universal width, depth and height, for example 22,6 cm by 18,6 cm by 244 cm. The building structure 100 further has a ceiling or roof comprising ceiling rulers 130, ceiling panels 131 , ceiling borders 132 and ceiling joists 135, the latter ceiling joists 135 spanning the ceiling panels 131 . The building structure 100 may serve as a temporary, affordable box-in-box housing that is built inside an existing, unused or empty building to solve the problem of shortage of social housings in cities. The building structure 100 may serve other purposes such as temporary office space, a workshop or atelier, a community centre, a pop-up store, a gallery or exhibition space, etc. When built box-in-box, the building structure 100 may be constructed without flooring as the existing flooring of the empty building may be used. When built outside or when built on uneven terrain, the building structure 100 will be built on floor elements. Such floor elements may be made of the parts used to built the ceiling, i.e. joists 135, horizontal panels 131 , and border parts 132, allowing to lay out the ground rulers 101 of building structure 100 horizontally. Such floor elements also may be used to build a second floor on top of the ceiling of building structure 100. Such second floor can than constitute an additional building structure, or it can be integrated with building structure 100 to create a multi-floor building structure, for instance a duplex.

[91] Fig. 2 shows in more detail the ground ruler 101 that is used in the building structure 100 of Fig. 1. The ground ruler 101 has a front side 201 , back side 202, bottom surface 203, top surface 204, and lateral sides 205, 206. The font side 201 and back side 202 are finished identically such that the ground ruler 101 can be used either with its front side 201 facing outside and its back side 202 facing inside, or vice versa. The top surface 204 of the ground ruler 101 has at least one cut-out 102, dimensioned and shaped to receive and hold the bottom surface of a vertical column 120, 121. Ground rulers of varying length may exist. Longer ground rulers shall have plural cut outs 102 whereas shorter ground rulers shall have only one cut-out 102 or no cut-out. The cut-outs 102 in the top surface 204 of such ground rulers are positioned such that the distance between neighbouring cut-outs 102 that form part of a single ground ruler or of neighbouring ground rulers with touching lateral sides corresponds to the universal width of a wall panel 110, 111 , 112. The cut-out 102 itself has a width corresponding to the width of a vertical column 120, 121 . [92] Fig. 3A shows a first wall panel 110 as used in the building structure 100 of Fig. 1 . The wall panel 110 is a basic wall panel having no openings or savings for doors or windows. The wall panel 110 has a front side, back side, bottom surface, top surface and lateral sides. The front side and back side have an identical finishing such that the wall panel 110 is symmetric and can be used either with its front side facing outward the building structure or with its back side facing outward the building structure. The lateral sides are provided with a pair of swallowtail connector protrusions. In Fig. 3A, the left lateral side has a first swallowtail connector protrusion 301 near the top surface, and a second swallowtail connector protrusion 302 near the bottom surface. The right lateral side has a third swallowtail connector protrusion 303 near the top surface and a fourth swallowtail connector protrusion 304 near the bottom surface. The swallowtail connector protrusions 301 -304 are shaped and dimensioned to engage with swallowtail connector notches in the vertical columns 120, 121 , as will be explained further below.

[93] Fig. 3B shows a second wall panel 111 as used in the building structure 100 of Fig. 1 . The wall panel 111 is a window wall panel having a single central opening 315 for a window. The wall panel 111 has a front side, back side, bottom surface, top surface and lateral sides. The front side and back side have an identical finishing such that the wall panel 111 is symmetric and can be used either with its front side facing outward the building structure 100 or with its back side facing outward the building structure 100. The lateral sides are provided with a pair of swallowtail connector protrusions. In Fig. 3B, the left lateral side has a first swallowtail connector protrusion 311 near the top surface, and a second swallowtail connector protrusion 312 near the bottom surface. The right lateral side has a third swallowtail connector protrusion 313 near the top surface and a fourth swallowtail connector protrusion 314 near the bottom surface. The swallowtail connector protrusions 311 -314 are shaped and dimensioned to engage with swallowtail connector notches in the vertical columns 120, 121 , as will be explained further below.

[94] Fig. 3C shows a third wall panel 112 as used in the building structure 100 of Fig. 1. The wall panel 112 is a door wall panel having a single opening 325 adapted to receive a door. The wall panel 112 has a front side, back side, bottom surface, top surface and lateral sides. The front side and back side have an identical finishing such that the wall panel 112 is symmetric and can be used either with its front side facing outward the building structure 100 or with its back side facing outward the building structure 100. The lateral sides are provided with a pair of swallowtail connector protrusions. In Fig. 3C, the left lateral side has a first swallowtail connector protrusion 321 near the top surface, and a second swallowtail connector protrusion 322 near the bottom surface. The right lateral side has a third swallowtail connector protrusion 323 near the top surface and a fourth swallowtail connector protrusion 324 near the bottom surface. The swallowtail connector protrusions 321 -324 are shaped and dimensioned to engage with swallowtail connector notches in the vertical columns 120, 121 , as will be explained further below.

[95] Fig. 3D represents an exploded view of wall panel 110. The wall panel 110 comprises a first sheet 341 that constitutes the front side of the wall panel 110, and a second sheet 342 that constitutes the back side of the wall panel 110. The first sheet 341 and second sheet 342 are separated by a wooden frame comprising a horizontal bottom beam 331 , a horizontal top beam 332, vertical lateral beams 333, 334 and vertical central beam 335. The space in between the first sheet 341 , second sheet 342 and the wooden frame is for instance filled with rock wool insulation panels, and a vapour barrier. The wall panel 110 may have a single vapour barrier. Alternative wall panels could be contemplated without any vapour barrier, or with two vapour barriers. In case of two vapour barriers, a first vapour barrier may be provided between the first sheet 341 and rock wool insulation panel and a second vapour barrier may be provided between the second sheet 342 and rock wool insulation panel. The wall panel 110 further has a first swallowtail connector protrusion in the wooden frame, more particularly in lateral beam 333, near the top surface, a second swallowtail connector protrusion, more particularly in lateral beam 333, near the bottom surface, a third swallowtail connector protrusion, more particularly in lateral beam 334, near the top surface, and a fourth swallowtail connector protrusion, more particularly in lateral beam 334, near the bottom surface. The vertical beams 333, 334 and 335 have horizontal holes 336 at a predetermined height that serve as a channel for conduits or ducts of various nature. The structure shown in Fig. 3D results in a wall panel with high mechanical strength, fire resistance against temperatures up to 1000 degrees Celcius, norm compliant thermal and acoustic insulation properties, and it does not disseminate toxic vapours.

[96] Fig. 4 shows in more detail the vertical column 120 used in the building structure 100. The vertical column 120 consists of two U-shaped parts 401 and 402, glued together at the top surface of the legs of the U-shape, such that a central opening or space 403 is created that serves as a vertical channel inside the vertical column 120. Fig. 4A and Fig. 4B respectively show the two U-shaped parts 401 and 402 before being glued to form vertical column 120. The first U-shaped part 401 has a first swallowtail connector notch 404, a second swallowtail connector notch 405, and a U- shaped channel or gutter 408. The second U-shaped part 402 is identical to the first U-shaped part, having a first swallowtail connector notch 406, a second swallowtail connector notch 407, and a U-shaped channel or gutter 409. The two identical U- shaped parts 401 and 402 allow to create the vertical connector column 120 of Fig. 4 that is used in building structure 120 to interconnect two wall panels that form part of the same wall or plane. This vertical connector column 120 has horizontal holes 410 at the predetermined height where also the vertical panels 110-112 have horizontal holes to serve as a pass-through channel for conduits or ducts.

[97] Fig. 5 shows in more detail the vertical column 121 used in the building structure 100. The vertical column 121 also consists of two U-shaped parts 501 and 502, glued together at the top surface of the legs of the U-shape, such that a central opening or space 503 is created that serves as a vertical channel inside the vertical column 121 . Fig. 5A and Fig. 5B respectively show the two U-shaped parts 501 and 502 before being glued to form vertical column 121 . The U-shaped part 501 shown in Fig. 5A also has a U-shaped channel or gutter 504, but does not have the swallowtail connector notches in its lateral surface 500. The second U-shaped part 502 shown in Fig. 5B is identical to the U-shaped part 402 of Fig. 4B, having a first swallowtail connector notch 506, a second swallowtail connector notch 507, and a U-shaped channel or gutter 505. The two U-shaped parts 501 and 502 allow to create the vertical column 121 that serves as an end column for a wall or in combination with a T-shaping part 800 to create a vertical corner column 123 that is used in building structure 120 to interconnect two wall panels that form part of different walls or planes placed under an angle of 90 degrees. This vertical column 121 also has horizontal holes 508, 509 in perpendicular directions at the predetermined height where also the vertical panels 110-112 have horizontal holes to serve as a pass-through channel for conduits or ducts in corners.

[98] Fig. 6 shows a top view of a vertical column 120. The first U-shaped part 401 and second U-shaped part 402 are glued together at the top surfaces 601 and 602 of the respective legs of the U-shapes. The first swallowtail connector notch 404 of U- shaped part 401 and the first swallowtail connector notch 406 of U-shaped part 402 represent swallowtail shaped cut-outs from the top surface of vertical column 120 into opposite lateral sides 603, 604 of the vertical column 120.

[99] Fig. 7A shows in more detail the swallowtail connector notch 404 in the U- shaped part 401 of vertical column 120. The swallowtail connector notch 404 has a bottom surface 701 that runs parallel with the lateral side 603 of the vertical column 120 wherein the notch 404 is provided. The swallowtail connector notch 404 further has a conical side surface 702 in between the lateral surface 603 of vertical column 120 and the bottom surface 701 of the swallowtail connector notch 404. The conical shaped side surface 702 is dimensioned to engage slidably with the conical shaped side surface of a swallowtail connector protrusion provided at lateral sides of wall panels near the top surface thereof.

[100] Fig. 7B shows in more detail the swallowtail connector notch 405 in U-shaped part 401 of the vertical column 120. The swallowtail connector notch 405 has a bottom surface 703 that runs parallel with the lateral side 603 of the vertical column 120 wherein the notch 405 is provided. The swallowtail connector notch 405 further has a side surface 704 in between the lateral surface 603 of vertical column 120 and the bottom surface 703 of the swallowtail connector notch 405, and substantially perpendicular to the lateral surface 603 and bottom surface 703. The swallowtail connector notch 405 near the bottom of the vertical column 120 is preferably dimensioned larger than the swallowtail connector notch 404 near the top surface of the vertical column 120. The swallowtail connector notch 405 is further dimensioned to engage with a swallowtail connector protrusion provided at lateral sides of wall panels, near the bottom of such wall panels. [101] Fig. 8 shows a T-shaping part 800 used for instance to create vertical corner columns 123 in the building structure 100. The T-shaping part 800 has a front side 801 , a back side 802, a bottom surface 803, a top surface 804, a first lateral side 805 and second lateral side 806. The first lateral side 805 has a flat surface that can be glued to the backside of a vertical column 120 or 121 consisting of two U-shaped parts. In case the U-shaped parts correspond to U-shaped parts 401 and 402, the T-shaping part 800 turns the vertical connector column 120 into a vertical T-column 122 that can be used to interconnect three wall panels, i.e. two wall panels that form part of the same wall or plane, and a third wall panel substantially perpendicular thereupon. In case the U-shaped parts correspond to U-shaped parts 501 and 502, the T-shaping part 800 turns the vertical end column 121 into a vertical corner column 123 that can be used to interconnect two wall panels substantially perpendicular to each other. In combination with the U-shaped parts 401 and 402, two T-shaping parts 800 can turn the vertical connector column 120 into a vertical cross column 124 that can be used to interconnect four wall panels, i.e. two wall panels that form part of the same plane, and a third and fourth wall panel that form part of a plane substantially perpendicular thereupon.

[102] Fig. 9A-9E show the five variant vertical columns that can be created using the U-shaped parts 401 , 402, 501 , 502 and T-shaping part 800. Fig. 9A shows a vertical connector column 120 that is created by gluing together U-shaped parts 401 and 402. Fig. 9B shows a vertical end column 121 that is created by gluing together U-shaped parts 501 and 502. Fig. 9C shows a vertical T-column 122 that is created by gluing together U-shaped parts 401 and 402, and by gluing T-shaping part 800 onto the backside thereof. Fig. 9D shows a vertical corner column 123 that is created by gluing together U-shaped parts 501 and 502, and by gluing T-shaping part 800 onto the back side thereof. Fig. 9E shows a vertical cross column 124 that is created by gluing together U-shaped parts 401 and 402, and by gluing two T-shaping parts 800 onto the frontside and backside thereof.

[103] Fig. 10 shows a ceiling ruler 130 as used in the building structure 100 of Fig. 1 . The ceiling ruler 130 has a front side 1001 , a backside 1002, a bottom surface 1003, a top surface 1004, and lateral sides 1005, 1006. The front side 1001 and backside 1002 have an identical finishing such that the ceiling ruler 130 can be used symmetrically. The bottom surface 1003 is shaped and dimensioned to engage with the top surface of wall panels and columns, whereas the top surface 1004 is kept flat. The bottom surface 1003 thereto is provided with protrusions 1007that engage with the top surface of columns. Variant ceiling rulers may have different lengths, with a maximum length of for instance 2,90 meters. The ceiling ruler 130 is placed on top of wall panels and vertical columns, leaving vertical channels in the columns open through holes 1008.

[104] Fig. 11 shows a ceiling border 132 as used in the building structure 100 of Fig. 1 . Variant ceiling borders may have different lengths.

[105] Fig. 12 illustrates a ceiling strip 134 as used in the building structure of Fig. 1. The ceiling strip 134 is made of fire resistant or fire-retardant material and serves as a positioning element on top of the ceiling panels 131 to indicate the position(s) where ceiling joists must be placed. The ceiling panels 131 are also made of fire resistant or fire-retardant material. Variant ceiling panels may have different dimensions able to span the width of a single wall panel or integer multiples of the width of a wall panel.

[106] Fig. 13A and Fig. 13B show variant ceiling joists 133 and 135 that form part of respective embodiments of the modular construction system according to the present invention. Whereas Fig. 13A shows a beam-shaped ceiling joist 133 that is easy to manufacture, Fig. 13B shows an l-profile shaped ceiling joist 135 that is more lightweight and therefore easier to transport and handle during the construction process. The joists may connect with the vertical columns using a pen.

[107] Fig. 14A-14I illustrate subsequent steps in an embodiment of the method for constructing a building structure according to the present invention. In a first step, illustrated by Fig. 14A, technicians lay-out the floor plan of the building structure using ground rulers 101 . The ground rulers used may have varying lengths. At least part of the ground rulers have one or plural cut-outs 102. The ground rulers 101 are positioned such that the cut-outs 102 appear at locations where vertical columns, i.e. structural elements interconnecting wall panels, must be placed. In a second step, illustrated by Fig. 14B, a first vertical column 123 is placed on a first cut-out 102 of a ground ruler 101. In the example of Fig. 14B, the first vertical column 123 corresponds to a corner column. In a third step, illustrated by Fig. 14C, two technicians are hanging a wall panel 111 onto the first vertical column 123. Thereto, the wall panel 111 is slightly lifted by the technicians and moved laterally such that a swallowtail connector protrusion 313 near the top surface of the wall panel 111 is resting on the top surface of the first vertical column 123. In a fourth step, illustrated by Fig. 14D, a second vertical column 120 is placed on the next cut-out 102 in the ground rulers 101 making up the ground plan. In the example of Fig. 14D, the second vertical column 120 is a connector column. During this fourth step, at least one technician shall continue to lift the wall panel 111 , while a second technician is placing the second vertical column 120 near the lifted wall panel 111. Once the second vertical column 102 is placed on the second cut-out 102, the second swallowtail connector protrusion 311 near the top surface of wall panel 111 can be made resting on the top surface of the second vertical column 120. At the end of the fourth step, the wall panel 111 is hanging in between two vertical columns 123, 120, with its top swallowtail connector protrusions 311 , 313 resting on the top surfaces of the vertical columns 120, 123. In the fifth step, illustrated by Fig. 14E, the wall panel 111 is released. The two technicians move the wall panel 1 11 such that the top swallowtail protrusions 311 , 313 slide into the top swallowtail notches of the vertical columns 120, 123, while the bottom swallowtail protrusions of the wall panel 111 engage with the bottom swallowtail notches of the vertical columns 120, 123. As a result thereof, wall panel 111 shall become fixed in between the vertical columns 120, 123, and its front and back sides shall be aligned with the front and back sides of the vertical columns over the entire height. At the end of the fifth step, the wall panel 111 shall rest on the ground ruler 101 . The ground ruler's top surface and the wall panel's bottom surface are preferably designed to engage with each other in order to further assist the alignment while releasing the wall panel 111. The third step (hanging a wall panel), fourth step (placing an additional column) and fifth step (releasing the wall panel) are thereafter iteratively repeated. This is for instance illustrated by Fig. 14F which shows the backside of corner column 123 consists of two U-shaped parts glued together, and a T-shaping part 800 with top swallowtail connector notch 807 and bottom swallowtail connector notch 808, glued against or otherwise placed against the backside of the two U-shaped parts. The T-shaping part 800 allows to mount a next wall panel under an angle of 90 degrees against wall panel 111. When all wall panels are placed, a technician places ceiling rulers 130 on top of the wall panels 110, 111 , as illustrated by Fig. 14G. Thereafter, the ceiling or roof is mounted. In the example illustrated by Fig. 14H, this is realized by first placing ceiling panels 131 on top of the ceiling rulers 130, placing ceiling strips 134 on top of the ceiling panels 131 at positions where ceiling joists must be placed, and placing beam shaped ceiling joists 133 on top of the ceiling strips 134. At the border of the ceiling or roof, border beams 132 are placed. In the example illustrated by Fig. 141, this is realized by placing ceiling panels 131 on top of the ceiling rulers 130, and placing l-profile shaped ceiling joists 135 on top of the ceiling panels 131 .

[108] Fig. 15A shows a first ground ruler element 1500 and a second ground ruler element 1550 used in a second embodiment of the building structure. The first ground ruler element 1500 has a front side 1501 , back side 1502, bottom surface 1503, top surface 1504, and lateral sides 1505, 1506. The top surface 1504 of the first ground ruler element 1500 has cut-outs 1507, extending in vertical direction along the back side 1502 and dimensioned and shaped to receive and hold extensions 1551 at lateral sides of the second ground ruler element 1550. The cut-outs 1507 in the first ground ruler element 1500 and extensions 1551 of the second ground ruler elements 1550 may for instance be dove-tail shaped. Ground ruler elements 1500 and 1550 of varying length may exist.

[109] Fig. 15B shows a ground structure of the second embodiment of the building structure. The ground structure comprises the first ground ruler element 1500 and second ground ruler element 1550 drawn in Fig. 15A. The ground structure further comprises ground joists 1520 that - similar to the second ground ruler element 1550 - have extensions at their lateral sides that connect with the cut-outs 1507 in the first ground ruler element 1500. The ground structure of the second embodiment further comprises a third ground ruler element 1510 that is glued onto the top surface 1504 of the first ground ruler element 1500. This third ground ruler element 1510 has cut-outs in its top surface, i.e. first circular holes 1511 at locations where vertical columns are expected, and has additional cut-outs in its top surface, i.e. second circular holes 1512 at locations where wall panels are expected, and has a milling line 1513 in its top surface that allows insertion of isolation material, a swelling band, a rubber strip, or the like, in order to improve the airtightness of the building structure. The first holes and second holes may have different or identical diameters in variant embodiments. The ground structure of the second embodiment further also comprises a fourth ground ruler element 1560 that is glued onto the top surface of the second ground ruler element 1550. This fourth ground ruler element 1560 has cut-outs in its top surface, i.e. circular holes 1561 at locations where wall panels are expected, and has a milling line 1562 in its top surface that allows insertion of isolation material, a swelling band, a rubber strip, or the like, in order to improve the airtightness of the building structure. The skilled person will appreciate that the fourth ground ruler element 1560 also may have cut-outs, i.e. holes, at locations where vertical columns are expected, these holes having a different or identical diameter to the holes 1561 for wall panels. Just like the first and second ground ruler elements, the third and fourth ground ruler elements may exist in varying lengths.

[110] It is further noticed that in situations where the modular building construction can be built on a flat surface, use of the first ground ruler element 1500 and second ground ruler element 1550 with joists 1520 in between may not be required. If the surface is flat, the third ground ruler element 1510 and fourth ground ruler element 1560 may be used to lay-out a ground plan on the flat surface. The third ground ruler element 1510 and fourth ground ruler element 1560 then form a simple ground ruler with cut-outs 1511 , 1512, 1561 in the top surface to receive vertical parts like columns and wall panels.

[111] Fig. 16A shows a first wall panel 1600 as used in the second embodiment of the building structure according to the invention. The wall panel 1600 is a basic wall panel having no openings or savings for doors or windows. The wall panel 1600 has a front side, back side, bottom surface, top surface and lateral sides. The front side and back side have an identical finishing such that the wall panel 1600 is symmetric and can be used either with its front side facing outward the building structure or with its back side facing outward the building structure. The lateral sides are provided with a pair of swallowtail connector protrusions. In Fig. 16A, the left lateral side has a first swallowtail connector protrusion 1601 near the top surface, and a second swallowtail connector protrusion 1602 near the bottom surface. The right lateral side has a third swallowtail connector protrusion 1603 near the top surface and a fourth swallowtail connector protrusion 1604 near the bottom surface. The swallowtail connector protrusions 1601 - 1604 are shaped and dimensioned to engage with swallowtail connector notches in vertical columns of the second embodiment, as will be explained further below. [112] Fig. 16B shows a second wall panel 1610 as used in the second embodiment of the building structure according to the invention. The wall panel 1610 is a window wall panel having a single central opening 1615 for a window. The wall panel 1610 has a front side, back side, bottom surface, top surface and lateral sides. The front side and back side have an identical finishing such that the wall panel 1610 is symmetric and can be used either with its front side facing outward the building structure or with its back side facing outward the building structure. The lateral sides are provided with a pair of swallowtail connector protrusions. In Fig. 16B, the left lateral side has a first swallowtail connector protrusion 1611 near the top surface, and a second swallowtail connector protrusion 1612 near the bottom surface. The right lateral side has a third swallowtail connector protrusion 1613 near the top surface and a fourth swallowtail connector protrusion 1614 near the bottom surface. The swallowtail connector protrusions 1611 -1614 are shaped and dimensioned to engage with swallowtail connector notches in vertical columns of the second embodiment, as will be explained further below.

[113] Fig. 16C shows a third wall panel 1620 as used in the second embodiment of the building structure. The wall panel 1620 is a door wall panel having a single opening 1625 adapted to receive a door. The wall panel 1620 has a front side, back side, bottom surface, top surface and lateral sides. The front side and back side have an identical finishing such that the wall panel 1620 is symmetric and can be used either with its front side facing outward the building structure or with its back side facing outward the building structure. The lateral sides are provided with a pair of swallowtail connector protrusions. In Fig. 16C, the left lateral side has a first swallowtail connector protrusion 1621 near the top surface, and a second swallowtail connector protrusion 1622 near the bottom surface. The right lateral side has a third swallowtail connector protrusion 1623 near the top surface and a fourth swallowtail connector protrusion 1624 near the bottom surface. The swallowtail connector protrusions 1621 -1624 are shaped and dimensioned to engage with swallowtail connector notches in vertical columns of the second embodiment, as will be explained further below. The third wall panel 1620 further has pins 1626 and 1627 at the bottom surface of the respective door jambs. These pins 1626 and 1627 are shaped and dimensioned to fit into the holes 1512 and 1561 for wall panels provided in the third and forth ground ruler elements 1510 and 1560, to provide additional stability to door panels 1620 installed in the building structure. The pins 1626, 1627 and holes 1512, 1561 provide a screwless and toolless connection between the door panel 1620 and ground ruler.

[114] Fig. 16D shows a fourth wall panel 1630 as used in the second embodiment of the building structure according to the invention. The wall panel 1630 is a large window wall panel having a single central opening 1635 establishing a large window. The wall panel 1630 has a front side, back side, bottom surface, top surface and lateral sides. The front side and back side have an identical finishing such that the wall panel 1630 is symmetric and can be used either with its front side facing outward the building structure or with its back side facing outward the building structure. The lateral sides are provided with a pair of swallowtail connector protrusions. In Fig. 16D, the left lateral side has a first swallowtail connector protrusion 1631 near the top surface, and a second swallowtail connector protrusion 1632 near the bottom surface. The right lateral side has a third swallowtail connector protrusion 1633 near the top surface and a fourth swallowtail connector protrusion 1634 near the bottom surface. The swallowtail connector protrusions 1631 -1634 are shaped and dimensioned to engage with swallowtail connector notches in vertical columns of the second embodiment, as will be explained further below. The large window wall panel 1630 shown in Fig. 16D has a width corresponding to twice the width of the wall panels 1600, 1610 and 1620 shown in Fig. 16A-16C plus the width of a vertical column 1700 as shown in Fig. 17A. Thereto, the large window wall panel 1630 is composed of a first wall element 1641 having the width of wall panels 1600, 1610, 1620, a second wall element 1642 having the width of wall panels 1600, 1610, 1620, a third wall element 1643 having the width of a vertical column, and a fourth wall element 1644 having the width of a vertical column. The third wall element 1643 is held below the large window 1635 between the first wall element 1641 and second wall element 1642 by two internal horizontal beams 1645 and 1646. The fourth wall element 1644 is held above the large window 1635 between the first wall element 1641 and second wall element 1642 by a third internal horizontal beam 1647. Like in other wall panels, a horizontal channel 1648 for conduits is created in wall panel 1630 at a predetermined first height.

[115] Fig. 17A-17E show in detail a vertical column 1700 used in the second embodiment of the building structure. The vertical column 1700 consists of two solid walls, 1701 and 1702, glued together by two flat panels, 1703 and 1704, such that a central opening or space 1705 is created that serves as a vertical channel inside the vertical column 1700. Fig. 17B shows the solid walls 1701 , 1702 and the flat panels 1703, 1704, before being glued to form vertical column 1700. The first solid wall 1701 , typically made of wood, has a first swallowtail connector notch 1706 near the top surface, a second swallowtail connector notch near the bottom surface, and a milling line 1712 running from its top surface to its bottom surface to hold isolation material, a swelling band, a rubber strip or the like, to improve the airtightness of the building structure. The second solid wall 1702 is identical to the first solid wall 1701 , having a first swallowtail connector notch 1708 near its top surface, a second swallowtail connector notch 1709 near its bottom surface, and a milling line 1711 running from its top surface to its bottom surface to hold isolation material, a swelling band, a rubber strip or the like, to improve the airtightness of the building structure. The two identical solid walls 1701 , 1702, glued together by the flat panels 1703, 1704 jointly create a vertical connector column 1700 that is used in the building structure to interconnect two wall panels that form part of the same wall or plane. This vertical connector column 1700 has horizontal holes 1710 at the predetermined height where also the vertical panels 1600, 1610, 1620, 1630 have horizontal holes to serve as a pass-through channel for conduits or ducts.

[116] Fig. 17C shows a top view of a vertical column 1700. The first solid wall 1701 and second solid wall 1702 are glued together via flat panels 1703 and 1704 such that a large central opening 1705 is created that may serve as vertical channel for conduits. The first swallowtail connector notch 1706 of solid wall 1701 and the first swallowtail connector notch 1708 of solid wall 1708 represent swallowtail shaped cut-outs from the top surface of vertical column 1700 into opposite lateral sides of the solid walls 1701 , 1702. Fig. 17C further shows the milling line 1712 in the first solid wall 1701 and the milling line 1711 in the second solid wall 1702, providing space for a vertical strip of air-tightening material like rubber or another isolating material.

[117] Fig. 17D shows in more detail the swallowtail connector notch 1708 in a solid wall 1702 of vertical column 1700, as provided near the top surface of vertical column 1700. The swallowtail connector notch 1708 has a bottom surface 1781 that runs parallel with the lateral side of the vertical column 1700 wherein the notch 1708 is provided. The swallowtail connector notch 1708 further has a conical side surface 1782 in between the lateral surface of vertical column 1700 and the bottom surface 1781 of the swallowtail connector notch 1708. The conical shaped side surface 1782 is dimensioned to engage slidably with the conical shaped side surface of a swallowtail connector protrusion provided at lateral sides of wall panels near the top surface thereof. As an alternative to the conical shape, the side surface 1782 may be substantially perpendicular to the bottom surface 1781 of swallowtail connector notch 1708 and substantially perpendicular to the lateral side of vertical column 1700 wherein the notch 1708 is provided.

[118] Fig. 17E shows in more detail the swallowtail connector notch 1709 in a solid wall 1702 of the vertical column 1700. The swallowtail connector notch 1709 has a bottom surface 1791 that runs parallel with the lateral side 1713 of the vertical column 1700 wherein the notch 1709 is provided. The swallowtail connector notch 1709 further has a side surface 1792 in between the lateral surface 1713 of vertical column 1700 and the bottom surface 1791 of the swallowtail connector notch 1709, and substantially perpendicular to the lateral surface 1713 and bottom surface 1791. The swallowtail connector notch 1709 near the bottom of the vertical column 1700 is preferably dimensioned larger than the swallowtail connector notch 1708 near the top surface of the vertical column 1700. The swallowtail connector notch 1709 is further dimensioned to engage with a swallowtail connector protrusion provided at lateral sides of wall panels, near the bottom of such wall panels.

[119] Fig. 18A-18D show four variant vertical columns that can be created using solid walls like 1701 and 1702, and flat panels like 1703 and 1704. Fig. 18A shows a vertical connector column 1700 that is created by gluing together two solid walls, 1701 and 1702, and two flat panels, 1703 and 1704. Fig. 18B shows a vertical T-column 1800 that is created by gluing together two solid walls, 1801 and 1802, and two flat panels, 1803 and 1804, and by gluing a third solid wall 1805 onto one of the flat panels 1803. Fig. 9C shows a vertical cross column 1810 that is created by gluing together two solid walls, 1811 and 1812, and two flat panels, 1813 and 1814, and by gluing a third solid wall 1815 onto a first flat panel 1813 and gluing a fourth solid wall 1816 onto a second flat panel 1814. Fig. 18D shows a vertical corner column 1820 that is created by gluing together two solid walls, 1821 and 1823, and two flat panels, 1822 and 1824, in such manner that the first solid wall 1821 and first flat panel 1822 represent opposite sides of the vertical column 1820, and the second solid wall 1823 and second flat panel 1824 also represent opposite sides of the vertical column 1820. Hence, two elements - the solid wall 1701 and flat panel 1703 - allow to create all vertical columns required in building construction. These vertical columns all have a central space that serves as channel for vertical conduits, and that is larger than the central space provided in the vertical columns of the above described first embodiment and therefore better accommodates all necessary conduits like electricity, gas, water supply, water drain, and sewage drain.

[120] Fig. 19 shows two ceiling ruler elements, 1900 and 1950, as used in the second embodiment of the building structure according to the invention. The first ceiling ruler element 1900 has a front side 1901 , a backside 1902, a bottom surface 1903, a top surface 1904, and lateral sides 1905, 1906. The top surface 1904 is provided with cut outs 1907 that extend vertically from the top surface 1904 along the back surface 1902, and that are shaped and dimensioned to engage with extensions 1951 at lateral surfaces of the second ceiling ruler element 1950. The cut-outs 1907 and extensions 1951 may for instance be realized through swallowtail shaped notches and protrusions, and jointly provide a tooth-and-groove connection. Variant ceiling ruler elements may have different lengths, with a maximum length of for instance 2,90 meters.

[121] Fig. 20 shows a ceiling joist 2000 that forms part of the second embodiment of the modular construction system according to the present invention. The ceiling joist 2000 may have a beam-shaped profile or an l-shaped profile, and further has a front surface 2001 , a back surface 2002, a bottom surface 2003, a top surface 2004, and lateral surfaces 2005 and 2006. The lateral surfaces 2005, 2006 have extensions or protrusions 2007 that are shaped and dimensioned to engage with the cut-outs 1907 in the first ceiling ruler element 1900 shown in Fig. 19.

[122] Fig. 21 shows the ceiling structure 2100 in the second embodiment of the building structure according to the present invention. In the ceiling structure 2100, ruler elements 1900 and 1950 are connected to form a ceiling border. Further, ceiling joists 2000 are connected to the first ceiling ruler element 1900 to form a rigid ceiling structure 2100. It is noticed that in preferred embodiments of the invention, the ground structure as illustrated in Fig. 15B and ceiling structure 2100 as illustrated in Fig. 21 are identical, as this reduces the amount of different elements used in the building structure substantially.

[123] Fig. 22A-22F illustrate subsequent steps in a second embodiment of the method for constructing a building structure according to the present invention. In a first step, illustrated by Fig. 22A, technicians lay-out the floor plan of the building structure using ground ruler elements 1500, 1550 and 1520. Ground ruler elements 1500 and 1550 are used to lay a ground border. Thereafter, ground joists 1520 are connected to ground ruler element 1500 through the tooth and groove connection 1507-1551 shown in Fig. 15B. On top of the ground ruler elements 1500 and 1550, respective ground ruler elements 1510 and 1560 are glued. In a second step, illustrated by Fig. 22B, a first vertical column 1820 is placed on ground ruler 1500. A pin attached to the bottom surface of vertical column 1820 or a separate pin may be used to establish a secure connection between the vertical column 1820 and the ground ruler. The pin thereto is inserted in hole 1511 of ground ruler element 1510. In the example of Fig. 22B, the first vertical column 1820 corresponds to a corner column. In a third step, illustrated by Fig. 22C, two technicians are hanging a wall panel 1610 onto the first vertical column 1820. Thereto, the wall panel 1610 is slightly lifted by the technicians and moved laterally such that a swallowtail connector protrusion 1613 near the top surface of the wall panel 1610 is resting on the top surface of the first vertical column 1820. In a fourth step, illustrated by Fig. 22D, a second vertical column 1700 is placed on the ground ruler 1500. In the example of Fig. 22D, the second vertical column 1700 is a connector column. During this fourth step, at least one technician shall continue to lift the wall panel 1610, while a second technician is placing the second vertical column 1700 near the lifted wall panel 1610. Once the second vertical column 1700 is placed on the ground ruler 1500, the second swallowtail connector protrusion 1611 near the top surface of wall panel 1610 can be made resting on the top surface of the second vertical column 1700. At the end of the fourth step, the wall panel 1610 is hanging in between two vertical columns 1700, 1820, with its top swallowtail connector protrusions 1611 , 1613 resting on the top surfaces of the vertical columns 1700, 1820. In the fifth step, illustrated by Fig. 22E, the wall panel 1610 is released. The two technicians move the wall panel 1610 such that the top swallowtail protrusions 1611 , 1613 slide into the top swallowtail notches of the vertical columns 1700, 1820, while the bottom swallowtail protrusions of the wall panel 1610 engage with the bottom swallowtail notches of the vertical columns 1700, 1820. As a result thereof, wall panel 1610 shall become fixed in between the vertical columns 1700, 1820, and its front and back sides shall be aligned with the front and back sides of the vertical columns over the entire height. At the end of the fifth step, the wall panel 1610 shall rest on the ground ruler 1500. The ground ruler's top surface and the wall panel's bottom surface are preferably designed to engage with each other in order to further assist the alignment while releasing the wall panel 1610. The third step (hanging a wall panel), fourth step (placing an additional column) and fifth step (releasing the wall panel) are thereafter iteratively repeated. This is for instance illustrated in Fig. 22F which shows a building structure wherein five wall panels 1610 have been placed. When all wall panels are placed, a technician places ceiling ruler elements 1900, 1950, 2000 on top of the wall panels 1610 and vertical columns. This is for instance illustrated in Fig. 22F where a first ceiling ruler element 1900 is placed on top of wall panels 1610.

[124] Although the present invention has been illustrated by reference to specific embodiments, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied with various changes and modifications without departing from the scope thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. In other words, it is contemplated to cover any and all modifications, variations or equivalents that fall within the scope of the basic underlying principles and whose essential attributes are claimed in this patent application. It will furthermore be understood by the reader of this patent application that the words "comprising" or "comprise" do not exclude other elements or steps, that the words "a" or "an" do not exclude a plurality, and that a single element, such as a computer system, a processor, or another integrated unit may fulfil the functions of several means recited in the claims. Any reference signs in the claims shall not be construed as limiting the respective claims concerned. The terms "first", "second", third", "a", "b", "c", and the like, when used in the description or in the claims are introduced to distinguish between similar elements or steps and are not necessarily describing a sequential or chronological order. Similarly, the terms "top", "bottom", "over", "under", and the like are introduced for descriptive purposes and not necessarily to denote relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and embodiments of the invention are capable of operating according to the present invention in other sequences, or in orientations different from the one(s) described or illustrated above.