BACKGROUND OF THE INVENTION

[0001] This invention relates to a prefabricated building unit, to a modular building system comprised of the building units and to a method of manufacturing the building unit.

BACKGROUND OF THE INVENTION

[0002] There is a demand for cheap and quick-to-erect building solutions that provide structures that can be used as affordable accommodation in projects such as, for example, university student accommodation and local and national government housing projects, granny-flats, teen pads, and holiday homes.

[0003] There have been several solutions to providing affordable accommodation which mainly have been centred around providing building components, such as bricks, wall-panels, roofing, and the like, which are comprised of cheap or re-cycled material and typically which interlock; not requiring cement or a mortar to fix the building components in place.

[0004] The problem these solutions is that, notwithstanding the relative ease with which these components are put together to construct the structure, some on-site expertise is still required. And, once the structure is erected, it needs to be retrofitted at least with electrical conduit and water supply piping [0005] Furthermore, there is often a limit on the number of levels or storeys that the structure provided by these solutions can attain.

[0006] The present invention at least partially addresses the problem.

SUMMARY OF INVENTION

[0007] The invention provides a prefabricated building unit which includes a cuboid body made of a cementitious material encasing a reinforcing steel frame, which body includes a four-sided wall component, defined between a quadrilateral top edge and bottom edge, and a quadrilateral roof-slab component, wherein an inner part of the top edge is formed with an inwardly facing rebate or step onto which the roof component rests and wherein an outer part of the top edge has a first inter-engaging formation.

[0008] The cuboid body may be square or rectangular.

[0009] The bottom edge may have a second inter-engaging formation.

[0010] The first inter-engaging formation may be a tongue or groove. The second inter-engaging formation may be a groove or a tongue respectively.

[0011] The four-sided wall component may have a width in a range 2.4m to 2.6m to fit on a truck for transportation. Preferably, the wall component has a width of 2.5m.

[0012] The wall component may include at least one aperture formed through at least one of sides of the component.

[0013] The at least one aperture may be a door or a window aperture. [0014] The roof-slab component may engage the step with a top surface of the roof-slab component flush with the top edge.

[0015] At each corner, the roof-slab component may be recessed to provide a corner gap between the roof-slab component and the four-sided wall component.

[0016] The roof-slab component may include at least one linear “inter-unit” conduit through which an electrical or electronic cable may pass, extending adjacent a side of the component and opening at each of its ends into a respective corner gap.

[0017] The roof-slab component may include at least one “intra-unit” conduit which extends between a terminal and a respective corner gap.

[0018] The four-sided wall component may have a plurality of holes, each hole in register with the at least one linear conduit.

[0019] The four-sided wall component may include at least one “intra-unit” conduit which extends between a terminal and a respective corner gap.

[0020] The terminal may be a plug, light-fitting point, or data point.

[0021] The four-sided wall component may have at a plurality of spaced hoist-attaching elements to which a hoisting sling is engaged for lifting the building unit onto a truck or lorry.

[0022] The reinforcing steel frame may be a box-frame. [0023] The box-frame may include insulation panels inserted between an inner and an outer surface of the frame.

[0024] In another aspect, the invention provides a modular building system which includes at least a first and a second building unit as described above, in which the first building unit is positioned on a ground surface and the second building unit is placed atop the first building unit with the first interengaging formation on the top edge of the first building unit engages the second inter-engaging formation on the bottom edge of the second building unit to prevent lateral movement of the second building unit relatively to the first building unit.

[0025] In a third aspect, the invention provides a method of manufacturing a building unit which includes the steps of:

(a) assembling a quadrangular inner shutter system on a platform,

(b) wrapping a steel mesh box-frame around an outer side of the inner shutter system,

(c) assembling a quadrangular outer shutter system around an outer side of the steel mesh frame,

(d) introducing a fluid cementitious material between the inner shutter system and the outer shutter system,

(e) dismantling the inner and outer shutter systems, once the cementitious material has set, to provide the building unit. [0026] The method includes the step of fixing window and door frames into the steel mesh box-frame, prior to introducing the fluid cementitious material.

[0027] The method includes the step of fixing conduits or inserting insulation panels into the steel mesh box-frame, prior to introducing the fluid cementitious material.

[0028] The method includes the step of providing a forming formation on the platform to form an interlocking formation on a bottom edge of the building unit.

[0029] In a fourth aspect, the invention provides a method of constructing a multi-storey structure which includes the steps of:

(a) providing at least a first building unit and a second building unit as described above;

(b) positioning the first building unit on a pre-laid ground slab; and

(c) lifting the second building unit onto the first building unit such that the groove or the tongue of the bottom edge of the second building unit engages with the tongue or the groove respectively of the top edge of the first building unit.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The invention is further described by way of examples with reference to the accompanying drawings in which: Figure 1 is an exploded view in perspective of a prefabricated building unit in accordance with the invention;

Figure 2 is a view in section, through line 2 - 2 on Figure 1 ;

Figure 3 is a view in perspective of a plurality of the building units of Figure 1 inter-engaged in construction of a structure;

Figure 3A is a view in longitudinal section through adjoining walls of a pair of stacked building units;

Figure 4 is a view in plan of corner sections of two adjacent units of Figure 3;

Figure 5 illustrates in perspective a plurality of building units, each with a different configuration;

Figure 6 illustrates a building unit being hoisted onto a truck for transportation;

Figure 7 is a view in plan of a base on which forming shutters are placed in the manufacture of building unit of Figure 1 ; and

Figures 8A to 8G sequentially illustrate the steps of a method of manufacturing the building unit of Figure 1 .

DESCRIPTION OF PREFERRED EMBODIMENTS

[0031] Figure 1 illustrates a prefabricated building unit 10 in accordance with the invention.

[0032] The prefabricated building unit 10 includes a cuboid body 12 which is made of a suitable steel reinforced cementitious material. The body includes a four-sided wall component 14 and a quadrilateral (square in this example) roof-slab component 16.

[0033] The four-sided wall component 14 is comprised of four wall sections, respectively designated 18A, 18B, 18C and 18D, each having an inner surface 20 and an outer surface 22. The wall component 14 extends in the vertical direction between a top edge 24 and a bottom edge 26.

[0034] The cuboid body 12 can be a square or rectangular in plan. The limitation is on the width of the body, which width should not significantly exceed the width of a typical transportation truck (see Figure 6) to be used in the transportation of the unit 10 from the factory to the location of a structure to be built using the units. In this example, the body has a width of 2.5 meters. The length can be variable, dependant on the requirement.

[0035] The roof-slab component 16 is defined between four edges, respectively 28A, 28B, 28C and 28D, and has an upper surface 30 and an under surface 32.

[0036] At each corner section (respectively designated 34A, 34B, 34C and 34D), the roof-slab component 16 is recessed to provide a plurality of orthogonally orientated stepped surfaces 36 (see Figure 4). The number of surfaces is dependent on the number of electrical cable conduit outlets that emerge at the respective corner section, as will be more fully described below.

[0037] With reference to Figure 2, adjacent the top edge 24 of the four-sided wall component 14, rebated into the inner surface 20, the walls are formed with a stepped recess 38, a horizontal surface of which provides a ledge 40. In addition, a ridge formation (“tongue”) 42 is provided, running along the entire top edge 24.

[0038] As a complementary structure to the ridge formation 42, a groove 44 is formed into the bottom edge 26 (see Figure 3A).

[0039] The slab component 16 is dimensioned to fit snugly into the stepped recess 38, coming to rest on the ledge 40. In an assembly of the slab component 16 with the walled component 14, the upper surface 30 is flush with the top edge 24 with only the tongue 42 projecting above this plane.

[0040] At each corner of the assembly, a corner gap 46 is provided between the stepped surfaces 36 of the slab component 16 and the walls 18 of the walled component 14.

[0041] In the example illustrated in Figure 1 , the walled component 14 has a door aperture 48 and a window aperture 50 formed through the wall 18D and the wall 18A respectively. The positioning, quantity and dimension of these apertures is dependent on the intended use and position of the unit within a structure. To illustrate this use and positional adaptability, Figure 5 shows a plurality of inter-leading units (respectively designated 10A, 10B, 10C 10N), each with a different configuration and quantity of door and/or window apertures (48, 50).

[0042] To provide for the feeding and containment of inter-unit supply-line electrical cable, data cabling, smoke detection wiring or the like (not shown), the slab component 16 includes a plurality of conduits (respectively designated 52A, 52B, 52C and 52D) (hereinafter referred to as “inter-unit conduits”). These inter-unit conduits are set within the slab component 16, at the time that the slab is thrown as will be described below, adjacent and running along each edge 28. It is not essential that each edge is provided with its counterpart conduit, with the decision on the number of inter-unit conduits provided in the slab dependant on the orientation of the unit 10 within the overall structure. It is preferable (but not necessarily cost effective), however, to set a conduit along each edge to ensure that no matter what the position and orientation of a unit, there will always be an inter-unit conduit orientated in the applicable supply line axis to be made use of. These supply line conduits 52 open at a respective stepped surface 36 of a respective corner section 34 (see Figure 4).

[0043] To provide for the feeding of an electrical cable (electronic wiring or data cabling) into an inter-unit conduit 52, a plurality of holes 56 (in Figure 4, illustrated in dotted outline) are formed through the respective wall 18 of the walled component 14, each hole aligned and in register with a respective conduit. This is best illustrated in Figure 4.

[0044] With reference to Figure 3, after construction of a multi-storey structure 54 with a plurality of building units 10.1 , 10.2 and 10.3, a supply-line electrical cable can be fed through the structure, as described, to electrically (or other relevant amenity) supply all units in the structure. This is achieved by, for example, making use of the aligned holes 56 and conduits 52 to feed the cable from, for example, unit 10.1 to unit 10.2. [0045] In addition to the inter-unit conduits 52, the slab component 16 and the wall component 12 include electrical wire conduits 57 (hereinafter referred to as intra-unit conduits). The slab component has an intra-unit conduit 57.1 which extends from a light terminal 58 to a respective surface 36 where it opens into a respective corner recess 46. The wall component has at least one electrical wire conduit 57.2 which extends from a plug point 62 (or light switch terminals) and which extends upwardly through the wall component, emerging at an opening 64 (see Figure 4) into a respective recess 46.

[0046] Adjacent each corner 64, the walled component 14 has a steel hoist engaging element 66 (such as a loop of hook), each of which is adapted to engage a respective end of a hoisting sling 68 (see Figure 6). When the unit 10 has been fabricated at the factory, and the cementitious material has set and cured, the unit is ready to be transported by truck to site. Lifting of the unit onto a truck 69 is achieved by using the hoisting sling, attached to a crane, which ends are attached to each of the hoist engaging elements. The unit is now ready to be hoisted onto a bed of the truck. The width dimension of the unit is orientated in the width direction of the truck’s bed.

[0047] On site, a plurality of units can be inter-engaged in construction of a multi-storey structure 54 such as that illustrated in Figure 3. In a first level, the unit 10.1 and 10.2 are lowered into position adjacent to one another, with respective inter-leading door apertures 48 providing an opening between the units. A third unit 10.3 is lowered onto the unit 10.2 whereupon the groove 44 of the bottom edge 26 of unit 10.3 engages with the tongue 42 of the top edge 24 of unit 10.2. The tongue and groove inter-engagement (see Figure 3A) prevents the upper unit sliding off the bottom unit due to a shear force. The slab component 16 of unit 10.2 provides a roof to this unit and a floor surface to unit 10.3.

[0048] With reference to Figures 8A to 8F, a method of manufacturing the building unit 10 in accordance with another aspect of the invention is described.

[0049] The walled component 14 is formed by pouring (or pumping from below) a fluid cementitious material between an inner shutter assembly 80, an outer shutter assembly 82, and a steel platform 84, and around a steel reinforcing mesh skeleton 86, located between the shutter assemblies. The cementitious material sets about the mesh skeleton. The mesh skeleton has an inner and an outer layer, respectively designated 88 and 90.

[0050] Before pouring the cementitious material, though, the inner and the outer shutter assemblies need to be assembled.

[0051] The inner shutter assembly 80 includes four panels, respectively designated 92.1 , 92.2, 92.3 and 92.4, which are joined to the steel platform by hinges 93, and four corner inserts, respectively designated 94.1 , 94.2, 94.3 and 94.4. The hinges allow for hinged movement of the panels from an upright to an inwardly titled position as is illustrated in Figure 8A.

[0052] The inserts 94 are fixed to respective edges of the panels to complete and rigidity the inner shutter assembly 80. This step is illustrated in Figure 8B and 8C. [0053] The steel platform provides a quadrangular forming ridge 96 which circumscribes the inner shutter assembly 80.

[0054] The mesh skeleton 86 is manufactured with lengths of rebar which are secured together, in a parallel manufacturing process, into a planar mesh wrap which, as illustrated in Figure 8D, is wrapped around the inner shutter assembly. Once fully enclosing the inner shutter, ends of the mesh skeleton are welded together to secure the skeleton in place.

[0055] Secured within the mesh skeleton is a window frame 89 and a door frame 91. Ultimately, when sandwiched between the inner and the outer shutter assemblies, the window and door frames will prevent flow of the cementitious material into a door or window aperture, thus providing, when the shutters are removed, the window 50 and the door 48.

[0056] Insulation panels (not illustrated) are positioned within a gap 96 between the inner and the outer layers (88, 90). Preferably, the panels are inserted into the gap after the mesh skeleton is made. The inner and outer layers of the skeleton are positioned on either side of the forming ridge 96. During this step in the method, this Inter- and intra- unit conduits (52, 57) are orientated within and fixed to the mesh skeleton to be cast therein. For ease of illustration, these conduits are not shown in Figure 8E.

[0057] The outer shutter assembly 82 comprises a pair of “L” shaped pieces (designated 98.1 , 98.2, 98.3 and 98.4) which are moved into position to enclose the mesh skeleton. This step is illustrated in Figure 8E and 8F. The outer shutter pieces are secured together along respective edges. Once correctly positioned with the aid of lugs on the platform (not shown), the L shaped pieces are sealed along respective lower edges to ensure that there is no egress of cementitious along this edge.

[0058] Before the cementitious material is poured, the inner shutter assembly 80 is braced internally (not shown) to withstand the inwardly directed forces generated by the mass of the filling material.

[0059] The assembly (illustrated in Figure 8F) is now ready to receive the fluid cementitious material which is input into the gap 96 to fill the entire depth of the gap, between the inner and the outer shutter assemblies (80, 82), flowing around and covering the mesh skeleton 86. To ensure that no part of the mesh skeleton remains exposed after the casting step, a few spacers (not shown) are provided, attached to the mesh skeleton, which uniformly space the mesh skeleton from the respective shutter assembly, thereby providing a space between the shutter and the skeleton into which the cementitious material can flow. In contrast, the window and the door frame (89, 91 ) are of sufficient thickness to abut both the inner and outer shutter so that no cementitious material flows inwardly of the respective frame.

[0060] Immediately after the cementitious material is input, a mould 100 (see Figure 8F) is placed atop the setting material, over the gap. This mould forms the ridge formation 42 on, and the stepped recess 38 within, the top edge 24.

[0061] Once the cementitious material has been allowed adequate time to set, the shutters are removed. The inner shutter assembly 80 is disassembled, with the corner inserts 94 removed and the panel 92 titled inwardly (see Figure 8G) away from the now manufactured walled component 14. Lifted off the platform 84 as described above, and with engagement of the roof-slab component 16, the building unit 10 of Figure 1 is provided.