Girder

The present invention relates to a girder for building purposes, comprising two mutually spaced elongated wood bands or members extending substantially parallel to each other and a sheet-like web rigidly interconnecting the bands.

Such girders are already known through for, example, U.S. Pat. No. 4,336,678, FR patent 1 230 119, and SE published patent application 389 883, and they are generally called "light girders". Girders of this type are used, instead of girders of solid wood, to achieve two main advantages which light girders have over solid girders. First, a "light girder" requires considerably less material and is therefore cheaper than a solid girder. As a consequence of this, it will of course be easier to handle because of its low weight. Secondly, because of the thin web a considerable reduction of thermal conductivity is obtained, i.e. conduction of heat (or cold) through the girder is made more difficult, as compared to the solid girders.

The girders hitherto known of the type mentioned in the introduction could only be used as walls, floors and the like when buildings were originally erected, but they could not be used for application on existing building surfaces, such as external walls or garret floors to effect additional insulation. The reason for not using the so called "light girders" for these purposes is that they could not be applied in a rational way by nailing, screwing or the like on a large existing surface. Solid girders have therefore been used in this type of additional works on existing buildings, and by that material as well as insulating capacity, are lost as compared to light girders.

The object of the present invention is to inconveniences mentioned above of the girders already known of provide a "light girder" which solves the problems of conventional girders and can be used on existing large building surfaces with the advantages discussed above. The light girder according to the invention is also well suited for use in, for example, roofs, walls and floors in the original erection of buildings.

Through the fact that the two elongated wood bands are arranged on opposite flat sides of the sheet-like web, it is easy to apply the girder according to the invention on a building surface through one of the two elongated wood bands, since the other band is not in the way when nailing, screwing or the like through the band in question, and at the same time the stability and rigidity of a plurality of spaced girder is assured by the transversal wood bands or member.

Preferably, but not necessary, the girder is applied on the building surface in question through the elongated wood band arranged on the opposite flat side of the web with respect to the transversal wood bands, since in such a case on one hand the transversal bands may not be in the way when applying the girder, irrespective of where this is accomplished along the elongated wood band, and on the other the elongated wood band located on the same side as the transversal bands may become the support from the transversal bands when applying an outer covering, such as a wall covering, on the outside of the frame work formed by several girders arranged on a building surface.

The girder according to the invention is naturally also adapted for new constructions, but it has the greatest advantages as compared to the girders of the prior art in the application on existing buildings, for instance in order to provide additional insulation.

Further advantages and advantageous characteristics of the invention will appear from the following description of a preferred embodiment of the invention.

With reference to the appended drawings, below follows a specific description of an embodiment according to the invention cited as an example.

In the drawings:

FIG. 1 is a perspective view of a preferred embodiment of the girder according to the invention.

FIG. 2 is a perspective view of the girder according to FIG. 1, but from the opposite direction.

FIG. 3 is a partially sectioned perspective view of the portion of an external wall of a building additionally insulated by means of girders according to the invention.

A girder 1 according to a preferred embodiment of the invention is shown in perspective from opposite directions in FIG. 1 and 2. The girder 1 has two mutually spaced elongated wood bands or members 2', 2" extending substantially parallel to each other and a sheet-like web 3, which preferably consists of a wood fiber board, for example of the type sold under the trade mark MASONITE, of a thickness of, for example 5 mm, interconnecting the bands 2', 2". The elongated wood bands 2', 2" are secured on opposite flat sides of the web 3, for instance by securing cramps, or staples which have been shot thereon by conventional cramp or staple guns, but gluing or the like is also possible. On the first flat side 4 of the web 3 a plurality of transversal or transverse wood bands or members 5 bearing upon the web 3 and extending substantially perpendicularly to the longitudinal direction of the bands 2', 2", from the first band 2' secured to the same flat side and to the opposite end of the web 3, are fixed at intervals. The transversal wood bands 5 are fixed on one hand to the first elongated band 2' by nails 6 (See FIG. 1), which have been driven through the elongated band 2' and into the transversal band 5 in question, and on the other to the web 3 and the second elongated band 2" by nails 7 (See FIG. 2), which have been driven into the transversal band 5 in question and through the web 3 and into the second elongated band 2". In this way a strong girder is obtained, and this strength may be adapted to the demands made by different conditions by varying the distance between the transversal wood bands 5 or the dimensions of the different parts of the girder.

It shall here be brought out clearly that the definition wood band also comprises bands composed by wood laminae, bands consisting of wood that have been broken up and then pressed together (of the particle board type) and bands of wood containing other materials, such as plastic or metals.

The further structure of the girder 1 shall now be explained with reference also to FIG. 3, which shows a number of girders 1 applied on an external wall 8 of a building for insulating purpose. Owing to the fact that the two elongated wood bands 2', 2" of the girder according to the invention are arranged on opposite flat sides of the web 3, it is possible to secure the girder on an existing surface in a very rational way, since good accessibility for example nailing is obtained in the region of the two elongated bands 2', 2". The girder is preferably nailed on an external wall 8 by applying the second elongated band 2" against the surface of the wall 8 and driving nails 9 through the band and 2" into the wall 8. A piece of the web 3 of the right girder shown in FIG. 3 has been broken away in order to illustrate this. Thereafter a covering 10 allowing humidity diffusion, such as any type of plates or cardboard, may be secured on the outside of the girders by nailing or the like into the first elongated band 2'. Subsequently, an external covering 15, e.g. wood panelling or siding is applied by nailing, screwing or the like in the bands 2' on the outside of the bands 2'. The transversal bands 5 will bear upon the external wall 8 through their surfaces 11 directed away from the band 2' and support the first elongated bands 2' in their supporting of the new external wall of the building. They do also prevent the first elongated band 2' from loosening from the web 3 upon the nailing of the wall coverings 10, 15.

The web of the girder according to the invention is provided with a number of through bores 12. Furthermore, the lower surface 13 of the transversal bands is obliquely directed with respect to the vertical line, preferably at about 45.degree. (See FIG. 2). The object of these two characteristics is to prevent air spaces from being formed during a method of providing additional insulation of external building walls according to the invention. In this method, after attaching the wall coverings 10, 15 outside the girders, an insulating composition or mass 14 is injected in the rooms formed between the girders 1, the previous external wall 8 and the wall coverings 10, 15. The bores 12 act as escape ways for the air present in these rooms or spaces, while the inclined lower surfaces 13 of the transversal bands 5 assure that no air spaces are formed under any transversal band on injection of the insulating material.

Thus, thanks to the provision of the girders 1 according to the invention it has become possible to utilize a totally new method of providing additional insulation to external walls of buildings. Previously, additional insulation boards were secured directly onto the house wall and after this a wall covering was secured to these, but since a house wall nearly always is uneven so called levelling has to be done, i.e. pieces of, for example, wood are placed behind certain girders in order to bring their external surface in the same plane as the other girders, which results in cavities between at least some of the insulating boards and the original wall surface behind them and through this results inferior insulation. The present invention avoids such inconveniences by means of the injection of the insulating material described above, which totally fills all the spaces between the previous and the new external wall.

The invention is of course not in any way restricted to the preferred embodiment described above, but a plurality of modification possibilities should be apparent to a person having ordinary skill in the art, without departing from the basic idea of the invention.

It would also be possible to apply the girder 1 according to the invention with the elongated wood bands arranged on the same flat side of the web as the transversal bands against existing building surface, if this would be desired.

By definition, "a web" also includes several sheet-like elements which may be arranged with a certain interruption between each other.

The shape of the transversal bands may, of course, be varied, and it is not necessary in every application that the web has through bores.

The girder 1 according to the invention may, of course, be used as an ordinary girder in erecting buildings or also for additional insulation of all kinds of surfaces, also including floors, roof frames and the like.

It would also be conceivable to arrange transversal bands 5 on both flat sides of the web 3. The insulating method according to the invention means that no exact girder distance is necessary, but this distance may be varied beyond the standard measures being imposed in conventional insulation as a result of certain dimensions of the insulating sheets or the like.