FIELD OF THE INVENTION

[0001] The invention relates to a prefabricated building element, the frame structure of which is made of wood and that may comprise insulation material. The elements can be utilized for making space elements, wall structures, floors, intermediate floors, ceilings and other parts of buildings or buildings themselves

[0002] Elements are used in many ways in the field of single family housing construction. The elements can be space elements or structure elements, such as walls, ceilings or floors. The space elements and structure elements are manufactured to the desired completion stage at the factory and assembled to form a complete building at the construction site. The advantage of space elements is their higher completion stage when delivered from the factory, but transporting them can be difficult and might require special arrangements. Space elements can easily be damaged during transport. Transport of structure elements is easier and in some cases the solutions wanted by the client can be realized more flexibly. The disadvantage is the increased amount of labour at the construction site and exposure to the conditions of the construction site. Building the wooden house elements is carried out by utilizing usual woodworking methods and the main advantage of element construction is achieved when the construction takes place in good conditions indoors at the factory.

[0003] CLT (Cross Laminated Timber) elements are one of the element construction methods. A CLT element made of solid lumber is formed by a number of lumber panel layers, the material thickness and number of which define the strength and thickness of the element. The structure of a CLT element is very strong and impermeable. The largest possible size of an element is 4.8 x 40.00 m and the thickness can be from 40 to 400 mm. The elements can be insulated, finished and provided with HVAC openings at the factory.

[0004] Due to their dense structure prefabricated CLT elements provide an easy way to build a passive-energy house, with no need for a separate air or vapour barrier. Due to the absence of cold bridges in the layer structure the CLT element functions as a part of the heat insulation of the building and improves the energy efficiency of the building. The massive lumber element allows a frame structure with a long service life and good fire resistance.

[0005] CLT creates new possibilities for design and flexibility of buildings. The stiffness of CLT allows high structures as well as large openings without additional stiffening members. Additionally extension, roof and staircase solutions without pillars can be made in horizontal structures. The frame material can be left visible or it can be lined. On the outside CLT buildings can be lined with lumber, plastered insulation or thin plaster panels. Due to its minimal expansion and compression CLT can easily be combined with other building materials, such as glass or steel. [0006] As CLT elements are formed of a massive lumber frame carrying the loads exposed on the structure and it usually also forms at least a part of the insulation capability of the structure, the element requires a large amount of wood as raw material. The element will be considerably heavy and making openings, such as doors and windows, is expensive, as a lot of massive waste material will be produced.

SHORT DESCRIPTION OF THE INVENTION

[0007] The invention is defined by the features of the independent claims. Some especial embodiments are described in the dependent claims.

[0008] According to the first feature of the invention there is provided a box- structure element comprising: a first surface panel, a second surface panel arranged at a distance from the first surface panel, and an intermediate structure attaching the first and second surface panel to each other and defining the distance between them, in which structure:

- the surface panels are lumber panels comprising at least three layers of lumber material glued on top of each other. [0009] According to the second feature of the invention there is provided an element wherein the surface panels are layered panel structures consisting of cross-laminated layers of sawn lumber having at least three superimposed layers.

[0010] According to the third feature of the invention there is provided an element in which each layer of lumber material consists of planar panels, preferably veneer.

[0011] According to the fourth feature of the invention there is provided an element in which the intermediate structure is massive timber.

[0012] According to the fifth feature of the invention there is provided an element in which the intermediate structure is glue-laminated timber. [0013] According to the sixth feature of the invention the intermediate structure forms at least one enclosed volume with the surface panels.

[0014] According to the seventh feature of the invention the intermediate structure comprises a surrounding timber around the edges of the element that joins the surface panels together. [0015] According to the eighth feature of the invention the volume between the surface panels and the intermediate structure is filled with insulation material.

[0016] According to the ninth feature of the invention there is provided an element in which the insulation material comprises wood shavings.

[0017] According to the tenth feature of the invention there is provided an element in which the insulation material is compressed wood shavings comprising bonding agent and having a specific weight of at least 200 kg/m ³ .

[0018] According to the eleventh feature of the invention the surrounding timber of at least one edge of the element is provided with a groove for a locking tenon.

[0019] According to the twelfth feature of the invention at least one bag or pressure volume is combined with the surrounding timber of at least one edge of the element so that it can be filled with a pressure medium, especially air or an expanding insulation material.

[0020] According to the thirteenth feature of the invention there is provided a building comprising at least two elements according to an embodiment of the invention, the elements being joined together and comprising at least one part of the building selected from the group: wall, floor, ceiling intermediate floor, intermediate wall.

[0021] According to the fourteenth embodiment of the invention the main directions of the grain of the lumber material of the lumber material layers of the surface panels are in adjacent layers at an angle with each other.

BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is an exploded view of an element according to some embodiments of the invention;

[0023] Figure 2 is a detail of figure 1;

[0024] Figures 3 and 4 illustrate the method of attachment used in some embodiments of the invention.

[0025] Figure 5 illustrates another method of attachment used in some embodiments of the invention.

EMBODFMENTS

[0026] DEFINITIONS

[0027] The structure of the massive lumber panel, CLT panel is defined as follows in the RIL 205-1-2009 instructions as follows: [0028] CLT is manufactured from finger-jointed strength-sorted spruce, fir or pine lumber. The strength class of the lamella in each layer is from C16 to C40. The thickness of the fully planed board is from 8 to 45 mm and the width of the board is at least 4 times the thickness. The crossing board layers are glued at an angle of 90 in relation to each other.

[0029] CLT has at least 2 and at most 20 layers of lamellae. The thickness of a CLT panel is from 16 mm to 350 mm. [0030] The cross-section is symmetrical. In a five-layer panel the two uppermost board layers may, at most, be parallel. When the panel comprises at least 7 layers of lamellae, no more than three superimposed layers may be parallel. The main portion of adjacent boards are glued to each other by their edges in a non-structural manner. The maximum allowed gap between adjacent boards is 2 mm for 10 % of the boards and a maximum of 4 mm for 3 % of the boards.

[0031] In this description a CLT panel means a layered panel structure consisting of cross-laminated lumber layers having at least three superimposed layers.

[0032] Plywood is a planar lumber product produced from at least three thin veneers by gluing them together.

[0033] The invention relates to a box-structure element of buildings, especially for a single-family house, terraced house or a small block of flats, the surfaces of the element being of CLT panel (cross-laminated timber). Preferably wood shavings are used as an insulation in the box structure. Wood shavings are a byproduct of wood processing industry. Using wood shavings is an ecological solution that increases its value added by processing. The box structure realizes an insulating, breathable and natural element with a minimized amount of joints. Tightness of the building is achieved without using plastics. Due to its tightness the element is a fire-safe construction solution.

[0034] Figures 1 and 2 illustrate one embodiment of the invention. In this embodiment the surface panels 1, 4 are CLT panel or cross-glued panel. In a cross-glued panel one lumber layer is formed of a panel formed of panels by means of a tongue and groove joint and in a cross-glued panel there are at least three of these layers glued one on top the other. In both or only one of the panels 1, 4 one or both surfaces of the panel can be of a high-quality wood for forming a high-quality surface or the surface panel can be made of wood of lesser value or even reject wood. In this case it is often necessary to finish the surfaces of the panels to suit the application. For example, residential buildings require a better surface quality then work environments or storage buildings. The surface panels can also be made of plywood or CIT panel. The panel structure must, however, consist of three lumber material layers. 24 mm can be used as a reference for minimum panel thickness. Thus the surface panel is dimensionally stable and dimensional movement doesn't break the paint surface or other finish of the surface. [0035] Due to the box structure the surface panels 1, 4 can be thin and light. Due to the structure and materials both the insulation and breathability are good because the sealed surface panels and, when necessary, total absence of joints in the surfaces produce such a tight a structure that the insulation is sufficient without sealing foils or the like. At the same time the element is, however, breathable due to its wood structure. Thin surface panels breath better than a fully massive lumber structure.

[0036] A box structure has been formed of the surface panels 1, 4 by means of a spacer structure. Here the spacer structure comprises a surrounding timber 3 running along the edges of the element and stiffening timbers 5. The surrounding timber 3 runs along the edge of the element either flush with the surface panels 1, 4 or at a distance inside from the edge. If the surrounding timber 3 is set flush with the edges of the surface panels the edge will be even, whereby the risk of damage to the surface panels is reduced and the edge is planar and tidy. However, if the surrounding timber 3 is pulled inside of the outer edge of the surface panel 1, 4, various attachment surfaces for attaching the elements to each other can be arranged into the formed groove. The surrounding timber 3 also runs around the openings 6 formed into the surface panels 1, 4 and thereby also to the element. The openings 6 can be doors, windows or other openings necessary for the building. The openings can be made into the surface panels by e.g. CNC machining methods, whereby they are fast and easy to make. In these places a surrounding timber 3 pulled inside from the edge of the opening 6 can be used for forming an installation collar for a window frame or door. The openings 6 of the surface panels 1, 4 can also be different in size so that a threshold or lip is formed in the corner of only one panel or surrounding timber 6. The box structure can be divided into subdivisions and its bearing capacity and strength can be varied by using the desired amount of stiffening timbers 5. The stiffening timbers 5 most preferably extend from one edge of the circumference formed by the framing timbers to the other edge. The stiffening timbers 5 can also act as a part of the surrounding timber 3 at the openings 6. Most preferably the surrounding timber 3 runs without interruptions along the edges of the surface panels and openings, but cuts and openings can be made thereto, if necessary, for pass-throughs or tubes. [0037] The dimensions and number of the surrounding timber 3 and the stiffening timber 5 define the thickness, stiffness and other strength properties of the element together with the dimensioning of the surface panels 1, 4. The width of the surrounding timber 3 and the stiffening timbers 5 sets the distance between the surface panels 1, 4 and their thickness changes the strength of the box structure. Stiffening timbers 5 are used to achieve a sufficient stiffness. On the other hand, it will be easier to later form openings between the stiffenings during the service life of the building. Thus a sufficient amount of compartments formed by the stiffening timbers increases the flexibility of the building for different requirements. The surrounding timber 3 and the stiffening timbers can be sawn lumber or glued timber produced by various means. Usual woodworking fastening methods can be used for attaching the surrounding timber 3, stiffening timbers 5 and the surface panels 1, 4, such as gluing, nails, screws, special connectors and shaped joints such as mitre joints. According to one embodiment the surface panels 1, 4 are fastened to the surrounding timber 3 and the stiffening timbers 5 by means of gluing. This produces a strong and tight structure and the method is well suitable for industrial production. Gluing produces an air-tight structure. If necessary, the gluing can be secured with screws.

[0038] According to one embodiment of the invention the spaces 7 formed by the surrounding timber 3 and the stiffening timbers 5 are filled with insulation 2. The insulation can be any suitable insulation, but as the element is otherwise a wooden structure, insulation materials based on natural fibers are preferable. According to one embodiment of the invention the insulation is wood shavings. Wood shavings are produced in various processes of wood processing industry. The shavings should be dry enough and it is preferable to remove fractions that are too small, especially dust. Compressing wood shavings and a bonding agent will produce a solid insulation. In the compression a mass of wood shavings having a specific density of about 100 kg/m ³ is compressed to about double density, whereby its specific density is increased to about 200 kg/m ³ . The necessary amount of bonding agent is very small. In one embodiment the bonding agent can be a fire- retardant agent, such as water glass or other commercially available fire suppression agent. The compression can be minimal, similar to the amount of the bonding agent, because their purpose is only to prevent the compression of the insulation during use. As the insulation is inside the box structure, it does not have to withstand mechanical stresses.

[0039] The insulation 2 can be compressed into ready pieces that are cut to the shape of the boxes of the element or the insulation 2 can be pressed directly into the boxes during manufacture of the elements. Insulation, like the other structures of the element, can be a fully natural material. In addition to the described shavings e.g. cellulose wadding, sheep wool, peat or plant-based fibre materials can be used as insulation. The compartments of the box structure of the elements, compression and bonding agent can be used for having an effect on the creeping of the insulation during use and for producing an element that retains its insulation capability. The advantage of wood shaving insulation is that the whole structure of the element is of the same material.

[0040] With massive timber a structure thickness of 280 mm is needed for achieving sufficient insulation. By means of a box element a similar structure thickness will produce a corresponding insulation. This will achieve considerable savings as the specific mass of massive timber is about 400 to 450 kg/m ³ . In a box structure the insulation forms a considerable part of the volume and its specific mass is of the order of 200 kg/m ³ . As all the parts of the element can be of same material, wood, the properties of the element are close to those of log structure. The box structure is stiff during transport and its surface panels work as the body of the element.

[0041] Byproduct flows and reject of wood processing industry can be utilized in the element, such as wood shavings as insulation and rejected or lower value sawn material can be used production of the surface panels. For example, surface panels can be made of lower quality, rejected or otherwise no-saleable panel. This allows using these materials for better profit than by e.g. burning them or selling them for a very low price.

[0042] The element can have a finished surface or the surfaces can be finished at the construction site. One surface structure of the outer wall can be ventilated board cladding.

[0043] Buildings and space elements can be assembled of the elements as necessary and the elements can be used in ceilings, floors and intermediate floors as well as in any structure in which stiffness of the element is required. For internal wall structures omitting the insulation material can be contemplated, but this will reduce sound insulation. Usual wood construction methods can be used for attaching the elements and insulating their joints. [0044] Figures 3 and 4 illustrate an attachment method of elements by means of which the embodiments of the invention can be carried out. In the example of figure 3 the first element 8 and the second element 10 are joined to each other in right angle so that the edge comprising the surrounding timber 3 of the first element will be against the surface panel 1 of the second element 10. Here the edge of the first element 8, the surrounding timber 3, is provided with grooves for tenons. Here they are two dovetail grooves 9. The edge of the second element 10 is provided with corresponding dovetail grooves 9 on the side of the surface panel. The elements 8, 10 must be sufficiently strong at their edge regions for forming the dovetail grooves 9. This can be guaranteed by using a sufficiently massive surrounding timber 3 extending to the grooves or by reinforcing the element at the dovetail grooves. The dovetail grooves can extend to the whole height of the element, whereby the keys can be installed by pushing from above. Here the tenons are butterfly tenons 11 consisting of two opposing triangular keys. When the tenons 11 extend to the whole length of the element joint, the joint will be strong along its whole length. The shape of the grooves and tenons may vary. The tenons can be, for example, an I profile in shape or shaped like bars with a web between them so that the cross-section of the bars is circular or semicircular. The essential point is that the grooves and tenons have surfaces that are pressed against each other. Preferably these surfaces are shaped so that a joint tightened by wedging is formed between the surfaces.

[0045] The essential feature of the joint described above is the pressure tightening gap 12 remaining between the tenon grooves 9 and the tenons arranged thereto and the surfaces of the elements. This pressure tightening gap can be provided with a bag filled with pressure medium or the pressure tightening gap can be filled with an expanding material, such as known insulation foams. The bag to be filled with pressure medium can be fastened between the tenon grooves already at the factory or it can be arranged at the location of the joint when attaching the elements. Compressed air is a preferred pressure medium, as it is usually available at construction sites and it's not harmful to health. However, liquid pressure or other pressure medium can also be used when necessary or the bag can be filled with an expanding insulation. Due to the length of the joint the area under pressure will be large, whereby a high tightening force can be achieved already with a small pressure. [0046] In figure 4 the edges of the elements are chamfered to an angle of 45°. The advantage of this is that the tenon grooves 9 can be made into the surrounding timber 3. The tenon grooves are perpendicular to the surface of the framing timber. The edges of the elements are similar.

[0047] The elements 8, 10 are joined as follows. The elements are aligned and installed with the tenon grooves 9 aligned and the tenons 11 are arranged in the grooves. Then the pressure tightening gap is pressurized by means of a pressure medium bag or expanding filler material. Now the pressure pushes the elements away from each other and the tenon groves are tightened to the tenons. When a sufficient tightening force has been reached, locking battens 13 are hit or pushed on both sides at the edges of the gap at the location of the joint for locking the joint and sealing the gap as well as finishing the appearance of the joint. As the joint is formed along the height of the whole element/the length of the joint, a strong and immobile joint is produced even though the forces exerted on the mating surfaces are reasonable.

[0048] Figure 5 illustrates an embodiment of the element and joining method in which one locking tenon is used, in this example a wide butterfly tenon 14. There are two pressure tightening gaps 15 and they are arranged at the bottom of the dovetail grooves 9 between the dovetail groove 9 and the butterfly tenon 14. In order to tighten the joint on both sides both elements 16, 17 to be joined must have a pressure tightening gap. The elements 16, 17 are joined otherwise in a corresponding way as in the above example, but now a tightening pressure must be formed into the pressure tightening gap 16, 17 of both elements. The pressure can be formed by similar methods as in the previous example, i.e. a pressure bag installed in the tightening gap 15 on site, a preinstalled pressure bag or expanding sealing agent. It can, of course, be contemplated that the gap between the locking tenon and the dovetail groove is made so accurately or provided with sealing members so that a tightening sufficient for the pressure medium is achieved. However, in this case the gap formed by the dovetail groove and the butterfly tenon must sufficiently sealed at both ends of the gap. The sealing can be provided by means of sealing members or wedges.

[0049] The joint is locked by means of locking battens or other wedge members, such as for example short wedge. The advantage of a long locking batten is the even distribution of forces along a long distance and small surface pressures. [0050] The various features and structures of the joining methods described above can be combined to form a joining method suitable for each joining application.

[0051] The strength and stiffness of the structure can be increased by fastening the element on the top plates or sill plates or other structures of the building, such as floor, intermediate ceiling or roof. These structures can also be formed of corresponding elements. [0052] The elements can be provided with boxes or tubes as well as openings for electrical and data communications cabling and, if necessary, with corresponding equipment for other HVAC equipment.

[0053]

INDUSTRIAL APPLICABILITY

[0054] At least some embodiments of the invention can be used for housing construction for forming various spaces and buildings.

REFERENCE NUMBER LIST