EP1831475A1

EP1831475A1 - Method and product in the erection of a building

Info

Publication number: EP1831475A1
Application number: EP05818164A
Authority: EP
Inventors: Timo MÄKINEN
Original assignee: Lahden Rakennus Passion Oy
Current assignee: Aariatalot Oy
Priority date: 2004-12-01
Filing date: 2005-12-01
Publication date: 2007-09-12
Also published as: WO2006058962A1; RU2007124600A; FI20041555A0; FI20041555A

Abstract

The invention concerns a method and a product in the erection of a building. In the method, the frame of the building is mainly constructed from beam pairs (1) consisting of floor beams (2) and external wall beams (4) hinged on each other by a hinge (6). On the building site, the wall elements (20) are assembled and, if desirable, given a surface treatment in a horizontal plane from standard building materials on the external wall beams (4). The wall elements (20) assembled in a horizontal plane, supported by the hinges (6), are lifted to an upright position, locked by means of locking screws (10) and joined to other wall elements (20) to form a continuous wall. The roof structure of the building is assembled and given a surface treatment on the wall elements (20) from the ground, lifted aside by means of a crane to allow the wall elements (20) to be lifted up, and finally lifted up onto the upright wall elements (20) to form the roof of the building.

Description

METHOD AND PRODUCT IN THE ERECTION OF A BUILDING

The present invention relates to a method as disclosed in the preamble of claim 1 and to a product as disclosed in the preamble of claim 8 for use in the erection of a building.

The method and product of the invention, hereinafter referred to by the common designation ^λsolution of the invention' , are particularly well applicable for use in the erection of a building to be built on a ventilated base floor. According to the invention, it is possible to build the floor, outer wall and roof structures of the building to a given degree of completion before the actual erection of the building. The solution of the invention is also usable with other types of base floor solutions.

In general, there are several alternative methods of constructing the floor, frame and roof structures of a building. These prior-art methods are often characterized in that the time spent on the construction project is quite long and skilled labor is needed for the construction work. A further drawback is that especially building work using scaffolding involves workplace accident risks and a poor working ergonomy. Yet another drawback is that the construction work is not efficient, because in connection with construction a large amount of waste material and construction waste is produced and additionally the construction costs are quite high.

According to prior art, building factories make prefabricated elements in a horizontal plane, but in this case the construction work has to be carried out by skilled labor and transporting the large elements to the building site is difficult and expensive. Moreover, mounting the large elements at the building site requires the use of an expensive crane as well as skilled labor. There are also prior-art methods, such as platform construction, wherein the frame structure of a wall is completed in a horizontal plane and the complete wall frame or part of a wall thus assembled is lifted in a single operation to an upright position to the place where it is to be mounted. In this solution less scaffolding is needed than in the traditional building method, but even this solution does not obviate the need for time-consuming measuring actions that may involve errors, because the length and position of each component, such as frame pole, intermediate member or equivalent, to be included in the frame have to be measured separately. In addition, in these solutions, too, the thermal insulation and weather stripping of the walls are made separately and utilizing scaffolds. This solution also requires the use of a specialized craftsman. A further drawback is that the materials, such as plywood and single wood, used in solutions applying the platform technology, are quite expensive.

The object of the present invention is to overcome some of the above-mentioned drawbacks and to create an efficient and workable method and a corresponding product in the erection of a building that are good and safe in respect of working ergonomy. A further object is to achieve a fast solution of economical price for the erection of a building. The method of the invention is characterized by what is disclosed in the characterization part of claim 1, and the product of the invention is characterized by what is disclosed in the characterization part of claim 8. Other embodiments of the invention are characterized by what is disclosed in the other claims.

The advantages of the solution of the invention include the fact that the building's wall structures together with wind shield boards and other necessary components can be built to completion in a horizontal plane, and thus, as compared to traditional building, the construction work is considerably faster, better and considerably safer in respect of working ergonomy, because the construction work can be carried out without using scaffolding, which often involves very laborious work, and there is no major risk of falling down during construction. A further advantage is that the outer surface structures of exterior walls, such as boarding and painting of boards, can be completed safely and very quickly in a horizontal plane. It is also an advantage that the building need not necessarily be provided with construction- time temporary structures, such as bracings, to keep the walls upright. Yet another significant advantage is that the construction work in a horizontal plane is carried out directly on the building site and the construction work can be executed without skilled labor. As the components of the frame structures delivered to the building site have largely been designed to standard dimensions so that they are the right size in both width, length and thickness, the only important detail is determination of the starting point, whereafter e.g. the floor beams and the frame structures of the walls as well as the wall panels and thermal insulation can be mounted directly on the elements to be built, without working them at all, and thus the traditionally required tools are not needed at the building site and the site remains free of construction waste, such as saw dust, plaster board or insulating material waste, produced by the working of materials. The standard dimensioning obviates the need to perform on the building site any dimensioning, which otherwise is normally a very rigorous and time-consuming task, because the pre-dimensioned structural components, when mounted on each other according to instructions, automatically bring the structures of the building to their designed dimensions. Furthermore, there is also the advantage that the entire roof structures of the building can, if desirable, be constructed and painted from the ground, which means savings in time and costs while a considerably better working safety in the construction work is achieved than in the traditional building method. A crane is thus only needed to lift off the roof structure completed on site from on top of the external wall elements of the building and to lift the completed roof structure into its position on the external wall elements lifted to an upright position.

The product to be manufactured, one important component of which is hereinafter called a beam pair, has the additional advantage that such beam pairs can be industrially manufactured using a very simple device. For the manufacture of the product, no heavy industrial infrastructure and no significant investments are needed. If necessary, the beam pair manufacture can be transferred to where raw material is available or a demand exists. The rest of the materials required for the structures consists of existing standard construction material. The beam pairs of the invention have been so designed that they can be packed in a mutually overlapping manner in a very compact transport package, with no empty space left between beam pairs.

In the following, the invention will be described in detail with reference to an embodiment example and the attached drawings, wherein

Fig. 1 presents an oblique side view of a beam pair according to the invention, turned to a partially open position,

Fig. 2 presents an oblique side view of beam pairs mounted side by side with even distances upon the foundation of a house, Fig. 3 presents an oblique side view of wall element constructed from beam pairs in a horizontal plane and provided with wall boarding on the outer surface, which element has not yet been lifted to an upright position to form an actual wall, Fig. 4 presents an oblique side view of the wall element of Fig. 3, lifted and locked to an upright position to form a complete wall element, Fig. 5 presents a wall element with a window opening for a side wall of a building as seen directly from inside the building,

Fig. β presents a sectional and simplified diagrammatic side view of a wall and floor structure constructed from a beam pair, with a roof structure mounted upon it, Fig. 7 presents a simplified diagrammatic cross-sectional view of a whole building as seen from the gable-end of the building, and Fig. 8 presents a simplified sectional view of the structure of a gable wall element of a building as seen from the side of the element.

All the figures presented are of a suggestive nature and they are not necessarily drawn in scale, nor do they necessarily represent the same construction.

Fig. 1 presents a beam pair 1 according to the invention, forming an important component, seen in an oblique top view and cut into two parts in the longitudinal direction. The beam pair 1 comprises a floor beam 2, which has on its lower surface a supporting batten 3 of a length substantially shorter at both ends than the floor beam 2. The supporting batten 3 is attached centrally to the floor beam 2 and is wider than the floor beam 2 so that the supporting battens 3 of two adjacent beam pairs 1 support a floor baseboard 11 to be mounted between the floor beams 2.

Pivoted by a hinge 6 on the upper surface of the floor beam 2 at a position close to the outer end of the floor beam is an external wall beam 4 having a thickness substantially equal to that of the floor beam 2 and a length so selected that the height of the finished wall will be substantially the same as a wall height according to standard construction. The external wall beam 4 consists of at least a wall frame beam 4a and an additional beam 5 attached to the outer surface of the frame beam 4a and having a thickness substantially corresponding to the thickness of the frame beam 4a.

The upper end of the frame beam 4a of the external wall beam 4 is provided with a rectangular cutout 7 made in the outer surface of the frame beam, whereafter the aforesaid additional beam 5 is fastened to the outer surface of the frame beam 4a. The length of the additional beam 5 has been fitted to be longer than the length of the frame beam 4a so that in the longitudinal direction each end of the additional beam 5 extends past the respective end of the frame beam 4a. Thus, the beam pair 1 in the collapsed position is a combination of four components placed one over the other, of which the two middlemost ones, i.e. the floor beam 2 and the frame beam 4a are hinged together by a hinge 6.

Fig. 2 presents three truncated beam pairs 1 according to the invention mounted on a foundation, such as a plinth structure, so that the base floor solution of the building is a so-called ventilated base floor. For the sake of clarity, the plinth structure is not shown in the drawing. The beam pairs 1 are placed at predetermined distances, substantially with spacing k-600 between them on the plinth structure in such manner that the floor baseboard 11 can be easily mounted afterwards between the beam pairs 1. Although the floor baseboard 11 has been depicted in Fig. 2 already at this stage of installation to give a better visual perception, it is often easier to mount the baseboards 11 e.g. only after the walls have been erected and the roof structure mounted in place. To mount the beam pairs 1, the horizontal distance between beam pairs is determined by means of tie plates 12 and 14, which come ready provided with markings showing the position of the midpoint or one side edge of the floor beam 2 of each beam pair. Thus, the floor beams 2 can be automatically placed at a correct distance from each other. The mounting work is started by placing the beam pair 1 adjacent to the gable end onto the marked point on the plinth structure. The tie plates 12 and 14 are fastened by their first ends to the ends of the floor beam 2 of the first beam pair, whereupon the next beam pair is positioned at the markings on the tie plates 12 and 14 secured by its ends to the tie plates 12 and 14. After this, a third beam pair is again placed at the next marking on the tie plates 12 and 14 and secured by its ends to the tie plates 12 and 14. Continuing this procedure, all the required beam pairs are placed in position. In this way, the outer tie plate 12 of the floor beams is fastened to the outer end 8 of each floor beam 2 and the inner tie plate 14 of the floor beams is fastened to the inner end 8 of each floor beam, the tie plates thus stiffening the floor beam assembly of the beam pair structure.

The position of the pivot of the hinge 6 has been so chosen that the distance from the pivot to the outer edge of the tie plate 12 of the floor beam 2 is substantially at least equal to the width of the frame beam 4a of the external wall beam. Thus, when the external wall beam 4 is being lifted to its upright position, the lower end 9 of the additional beam 5 comprised in the external wall beam 4 will stop the external wall beam at exactly the right angle, which is substantially a right angle. The inner edge of the additional beam 5 of the uplifted external wall beam 4 is thus in the vertical plane substantially in the same line with the outer surface of the tie plate 12 at the outer end 8 of the floor beam 2.

Fig. 3 presents a finished wall element 20 assembled from beam pairs 1 on the building site and containing beam pairs 1 according to Fig. 2, mutually secured at predetermined distances between them and braced by tie plates 12 and 14. The external wall beams 4 of the beam pairs are mutually braced by an overhead cross-bracing beam 13, which is placed in notches 7 made in the outer surface of the frame beams 4a. The overhead cross-bracing beam 13 is secured to the external wall beams 4 e.g. by screwing or nailing through the additional beams 5.

A wind shield board 17 of standard width and length is fastened to the outer surfaces of the additional beams 5. The lower edge of the wind shield board 17 ends at the same level as the lower surfaces of the additional beams 5 and its upper edge ends at the same level as the upper surfaces of the additional beams 5. The standard width of the wind shield board is substantially exactly the same as the width of the three beam pairs 1 mounted on the foundation and secured to each other. Ventilating strips 15 of a length substantially equal to that of the wind shield board 17 are fastened onto the wind shield board 17 at a position and in an orientation corresponding to the position and orientation of the external wall beams 4 under the wind shield board 17. External cladding panels 16 are correspondingly fastened onto the ventilating strips 15, but at this stage the lowest board of the panels is preferably left out to allow the wall elements 20 to be more easily locked in the upright position. The boards of the external cladding panel 16 have a length substantially equal to the total width of the three beam pairs 1 mounted on the foundation and fastened to each other. The panel boards of the external cladding panel 16 are given a surface treatment, e.g. painted before the wall element 20 is lifted to the upright position.

In addition, a locking screw 10 provided with a washer or equivalent is screwed into the lower end of the ventilating strip 15, which screw is used to lock the uplifted wall element 20 in the upright position. Substantially all the above-mentioned stages of work explained with reference to Fig. 3 are carried out in a horizontal plane before the completed wall element 20 is lifted to its upright position. It is advantageous to build substantially all the wall elements 20 of the side walls to completion at once before lifting the wall elements to the upright position. Before lifting up the elements, it is additionally preferable to brace the wall elements 20 and fasten the elements so as to form wall elements of desired size by securing bracing beams 18 to the top end of the wall elements. The bracing beams 18 make the structure sturdier and allow the wall elements to be more easily lifted to the upright position. For the sake of clarity, Fig. 3 shows the situation before the mounting of the bracing beams 18.

In Fig. 4, the completed wall element 20 has been lifted as a single element to its upright position and secured at a substantially right angle relative to the floor beams 2 by means of locking screws 10. Thermal insulation, plastic lining and interior wall paneling of standard width are placed in the spaces between the external wall beams 4, against the wind shield board 17. An essential point is that the positioning and dimensioning or the beam pairs 1 have been so adapted as to allow thermal insulation and interior wall panel materials of standard width and length to be mounted on the wall element 20 without substantial working and dimensioning at the building site. On the external wall of the building, vertical cladding boards are mounted over the vertical joints between the wall elements 20 to cover the gaps between adjacent external cladding panels 16.

Fig. 5 presents a wall element 32 with a window opening for a side wall of a building as seen directly from inside the building. A window opening 27 is made in the wall element 32 in the area of three or more external wall beams 4. The external wall beams 31 below the window opening 27 are fastened to the floor beams 2 in the same way as the normal external wall beams 4 and they end below the window opening 27 to support the lower window beam 30. The lower window beam 30 is secured to the external wall beams 4 and 31. The external wall beams 28 above the window opening 27 are fastened to the wall element 32 via an overhead cross- bracing beam 13. The upper window beam 29 is secured to the external wall beams 4 and 28. The wind shield board 17b below the window opening 27 is fastened to the external wall beams 4 and 31 and to the upper window beam 30. The wind shield board 17a above the window opening 27 is fastened to the external wall beams 4 and 28 and to the upper window beam 29. A tie beam 18 mounted in a horizontal position at the upper end of the wall elements ties the wall element 32 with a window opening to the other wall elements 20.

Fig. 6 presents a simplified sectional view of a building's side wall constructed from uplifted wall elements 20 and 32, as well as floor structures and roof structures. All the wall elements 20 and 32 of the side wall are secured to each other via a horizontal tie beam 18 at the upper end of the external wall beams so as to form a unitary wall assembly. The roof structure already built to completion is lifted onto the tie beams 18 and secured in its proper place.

Fig. 7 presents a simplified cross-sectional view the wall structures, floor structures and rafter beams 19 of a building as seen from the gable-end of the building. The floor beams 2, which are fastened to the side walls of the building, i.e. to the beam pairs 1, have been made to predetermined dimensions and their length is determined by the length of the external wall beams 4 of the beam pairs 1, this length being consistent with the standard dimensioning. The final width of the building is determined according to the length of the middlemost floor beams 21 mounted between the opposite beam pairs 1 placed on different sides of the building. However, this length is so adapted that the width of the building is in exact agreement with the standard spacing of the wall beams. The middlemost floor beams 21 are substantially aligned with the outermost floor beams 2 and their lower surfaces are provided with corresponding supporting battens 3, to which the floor baseboards 11 are secured as in the case of the outermost floor beams 2. Placed between the middlemost floor beams 21 and the outermost floor beams 2 are tie plates 14 transverse to the floor beams to stiffen the floor structures.

In the method of the invention, the main parts of the roof structures can be built from the ground. The rafters 19 are lifted onto the completed wall elements 20 before lifting the wall elements 20 to the upright position. The rafters 19 are placed on the wall elements 20 with spacing k-900. Depending on the size of the building, it ^■ may also be necessary to have a compensating spacing below k-900. This compensating spacing can be dimensioned e.g. by the traditional measuring method. The work stage can be carried out without using a crane, because the roof rafters need not be lifted to a great height. The roof structures can thus be built to completion. Likewise, the surface treatment of the roof structures, such as painting of the gables, can be performed from the ground. The finished and assembled roof structure is lifted off the wall elements 20 by using e.g. ropes and a crane.

After the roof structure has been lifted off the wall elements 20, the wall elements 20 are lifted up about the hinges and locked to the upright position.^' If the tie beams 18 have not yet been fastened to the upper end of the wall elements 20, then they have to be fastened now. ^' The tie beams 18 lock the wall elements 20 together as a single assembly. Once the wall elements 20 are in the upright position and the tie beams _. have been secured in place, the completed roof structure is lifted by means of a crane onto the tie beams 18 and secured in position.

An exception to building the roof structure from the ground is the mounting of tile roofing, because, due to the heavy^¬ weight of the material, tile roofing is appropriately mounted by the traditional technique only after the roof structures have been lifted up onto the tie beams 18. Likewise, a large and heavy roof structure is preferably built by the traditional technique, because it may be difficult to lift up a heavy roof structure with a large surface area.

After the roof has been mounted, the floor baseboards 11 can be secured in place e.g. with screws to the supporting battens 3 attached to the floor beams 2. Next, the thermal insulation of the floor is mounted on the floor baseboards 11, in the spaces between the floor beams 2, using standard- width thermal insulation material. The floor of the building is built on the floor beams 2 using prior-art techniques.

The figures described above illustrate the assembly and erection of the wall elements 20 of the long walls, i.e. side walls of a building on the construction site. After the erection of the wall elements 20 and the lifting of the roof structures, the end wall elements 24 are built as illustrated in Fig. 8. The external wall beams 23 of the end walls of the building, which were not yet connected by hinges to the floor beams 2 and 21 in the factory delivery, are fastened to the outermost floor beams 2 and 21, i.e. to the floor beams closest to the end of the building. The outermost floor beams 2 and 21 at each end of the building are provided with markings spaced at equal distances showing the positions where the external wall beams 23 are to be mounted and the positions for the hinges 22 to be fastened to the mounting positions. Alternatively, hinges 22 spaced at equal distances are mounted on these floor beams 2 and 21 already at the factory, to which hinges the external wall beams 23 of the end walls are secured by their lower parts. After the external wall beams 23 of the end walls have been fastened, the end wall elements 24 are constructed in a substantially horizontal plane and erected like the wall elements 20 of the long walls of the building. The external wall beams 23 of the uplifted end wall elements 24 are supported on a sole 25 secured onto the foundation, such as a plinth 26, and they are locked in their upright position by means of fastening elements 33, such as nails or screws, from the inner side of the floor beams 2 and 21.

It is obvious to the person skilled in the art that the invention is not exclusively limited to the embodiment examples described above, but that it may be varied within the scope of the claims presented below. Thus, for example the wall elements 20 may be made in widths other than those mentioned in the embodiment examples described above. By difference from Figs. 3 and 4, one wall element can be advantageously constructed e.g. by connecting five or seven external wall beams 4 together by means of an overhead cross-bracing beam 13 and a tie beam 18 before lifting the wall element 20 to the upright position. Also, four, six or more external wall beams can be connected together before the wall elements are lifted to the upright position.

It is likewise obvious to the skilled person that the paneling 16 forming the external cladding may also be implemented by various vertical paneling methods, in which case the external wall structure is provided with ventilating strips in the horizontal direction as well. In this way, a continuous cladding paneling 16 covering the entire length or the wall is obtained, and no separate cladding boards are needed over the gaps between the wall elements 20 and 24.

It is additionally obvious to the person skilled in the art that the external cladding can also be made after the erection of the wall elements, in which case it is possible to use longer cladding panels on the wall surface than those described above in the example according to Fig. 3. Moreover, the external cladding can also be made from other materials than paneling boards, e.g. from tiles, ashlars or bricks, or the external cladding may be combination of several materials.

It is also obvious to the skilled person that most of the components, such as e.g. the baseboards 11 and tie beams 18 can be mounted in different ways and in a different order than in the examples described above.

Claims

1. A method in the erection of a building on a foundation, in which method at least the floor structure and the frame structure of the external walls of the building are assembled and erected, characterized in that at least part of the floor structure and external wall structure is made on the building site from beam pairs (1) consisting of floor beams (2) and external wall beams (4) hinged on each other, by placing the beam pairs (1) at predetermined horizontal distances from each other and fastening the essential structures of the external wall in a substantially horizontal plane to the external wall beams (4) on the floor beams (2) .

2. A method according to claim 1, characterized in that at least mutually adjacent floor beams (2) are connected by their ends with tie plates (12, 14), said tie plates being provided with markings showing the fastening points of the ends of the floor beams (2) so that, after the tie plates (12, 14) have been secured, the distances of the beam pairs (1) from each other are consistent with standard distances in the construction industry.

3. A method according to claim 1 or 2, characterized in that an assembly of at least two external wall beams (4) is built at a time in a substantially horizontal plane on the floor beams (2) in such manner that an overhead cross-bracing beam (13) connecting the upper ends of the external wall beams (4) is fastened to a cutout (7) provided at least at the upper end of the external wall beams (4) and a wind shield board (17) or equivalent is fastened to the outer surface of the external wall beam (4), and that, if desirable, ventilating strips (15) and an external cladding (16) are fastened to the outer surface of the wind shield board (17) or equivalent, whereupon the wall element (20) thus assembled, supported by hinges (6) mounted between the external wall beams (4) and the floor beams (2) , is lifted to an upright position and locked in the upright position by- means of locking screws (10) , and that the wall elements (20) are fastened together by their upper ends by means of tie beams (18) .

4. A method according to claim 1, 2 or 3, characterized in that, to form an external cladding (16), panel boarding is mounted in a substantially horizontal position and the external cladding (16) is coated in a substantially horizontal position by painting or by using a corresponding coating.

5. A method according to any one of the preceding claims, characterized in that the beam pairs (1) mounted on the foundation are braced to each other by means of tie plates

(12) fastened to the outside of the floor beams (2) and tie plates (14) fastened to the inside of the floor beams, and that, in the middle part of the building, a substantially straight middlemost floor beam (21) is mounted between the floor beams (2) of the beam pairs (1) on opposite sides of the building and fastened to the tie plates (14) , the total width of the building being determined by the length of said middlemost floor beam.

6. A method according to any one of the preceding claims, characterized in that the roof rafters (19) of the building are placed onto the wall elements (20) in a horizontal plane in such manner that the beam pairs (1) and middlemost floor beams (21) dimensioned and placed on the foundation during a previous building stage are substantially parallel to the roof rafters (19) , and that the roof structure of the building is assembled and given a surface treatment, such as painting, from the ground at least on the wall elements (20) in a horizontal plane and lifted aside to allow the wall elements (20) to be lifted to an upright position, whereupon the roof structure is lifted to its proper position on the wall elements (20) lifted to the upright position.

7. A method according to any one of the preceding claims, characterized in that external wall beams (23) are mounted at the gable ends of the building by fastening the external wall beams (23) by means of hinges (22) to positions on the outermost floor beams (2, 21) marked either by the hinges (22) or other suitable markings at predetermined distances from each other to facilitate the fastening, and that an assembly of at least two external wall beams (4) is built at a time in a substantially horizontal plane on the floor beams (2, 21) in such manner that a wind shield board (17) or equivalent is fastened to the outer surface of the external wall beam (23) , and that, if desirable, ventilating strips (15) and an external cladding (16) are fastened to the outer surface of the wind shield board (17) or equivalent, whereupon the wall element (24) thus assembled, supported by the hinges (22) mounted between the external wall beams (23) and the floor beams (2, 21), is lifted to an upright position and locked in the upright position by means of locking elements (33) , such as nails or screws, from the inner side of the floor beams (2, 21) and that the wall elements (24) are fastened together by their upper ends by means of tie beams (18) .

8. A product in the erection of a building, said product comprising at least a part forming a floor beam (2) of the building, characterized in that an external wall beam (4) has been fitted to be pivoted by a hinge (6) on the floor beam (2) .

9. A product according to claim 8, characterized in that the floor beam (2) and external wall beam (4) pivoted on each other by the hinge (6) have been fitted to form a beam pair (1), wherein the length of the external wall beam (4) has been so chosen that the height of the completed wall will be substantially the same as a wall height according to standard construction.

10. A product according to claim 8 or 9, characterized in that the floor beam (2) has on its lower surface a supporting batten (3) of a length substantially shorter at both ends than the floor beam (2) , said supporting batten (3) being attached centrally to the floor beam (2) and said supporting batten (3) being wider than the floor beam (2) , and that the external wall beam (4) comprises a frame beam (4a) provided with a cutout (7) in its outer surface at least at the upper end and an additional beam (5) fastened to the outer surface of the frame beam (4a) and having a width substantially equal to that of the frame beam (4a) , the length of which frame beam extends at each end past the end of the frame beam (4a), and that the beam pair (1) formed by the floor beam (2) and the external wall beam (4) is in the collapsed position a combination of four components placed one over the other, of which the two middlemost components, i.e. the floor beam (2) and the frame beam (4a), are hinged together by a hinge (6) .

11. A product according to any one of the preceding claims 8 - 10, characterized in that at least two adjacent floor beams (2) have been fastened together at their outer ends with a tie plate (12), and that the hinge (6) has been fastened to a point on the upper surface of the floor beam (2) such that the distance from the pivot of the hinge (6) to the outer edge of the tie plate (12) of the floor beam (2) is substantially at least equal to the width of the frame beam (4a) of the external wall beam (4) .