Background of the invention

The invention relates to a rectangular building element which com prises a surface board forming a first facing surface located oppositely to a second facing surface of the building element; a first edge surface on a first edge, which is located oppositely to a second edge surface on a second edge; a third edge surface on a third edge, which is located oppositely to a fourth edge surface on a fourth edge; heat insulation material between the first facing surface and the second fac ing surface, the heat insulation material comprising building foam; and a plurality of rectangular, longitudinal support structures arranged at a distance from each other, which in a vertical position extend between the first edge surface and second edge surface of the building element, the support structures being bound together by the building foam, and top surfaces of the support structures being arranged at a distance from a bottom surface of the surface board by means of the building foam. The building element may typically be an intermediate floor element (a floor panel), a roofing deck, or a base floor element (base floor).

The rectangular-shaped slab-like building elements, which contain a heat insulation material, are well known and their detailed structure may in prac tise greatly vary. The heat insulation material in building elements is often mineral wool or glass wool whose purpose, as the name suggests, is to prevent heat transfer between the opposite facing surfaces of the building element. The building element of the type referred to in the above, which comprises building foam as the heat in sulation material and a plurality of support structures bound to each other by means of building foam, is known from the publication US 5678369 A.

Even though the heat insulation material also features a soundproofing property, in practise the soundproofing property of the known building elements is modest. In particular, if the building element is used as an intermediate floor el ement, it is of common knowledge that the soundproofing property against struc ture-borne noise is not as good as is desirable. In practise, this manifests itself so that sound is carried vertically from one floor/apartment to the next in a multisto rey building. Hollow-core concrete slabs do provide better soundproofing than wood-framed elements but not even concrete elements can effectively prevent sound transmission from a storey to the next when the sound is caused by impacts on the top surface of the concrete slab, created by walking on the concrete slab with high-heel shoes or shoes having a hard bottom. Under such conditions, walking on a floor higher up causes impact sounds to be heard as unpleasant knocking on the floor below.

It is the purpose of the present invention to provide a new building ele ment whose ability to insulate sound is in practise substantially better than with known building elements.

Brief description of the invention

It is an object of the invention to provide a building element to be used in housing construction, in particular, and able to efficiently isolate sound consist ing of several sources of sound, including impact sounds. This object of the inven tion is achieved by a building element of the type described in the above, which according to the invention is characterized in that there is sand between adjacent support structures, which forms soundproofing adjacent layers of sand between the support structures, the layers being supported from below by the building foam and covered by the building foam.

Advantageously, the layers of sand extend from the first edge surface to the second edge surface of the building element, because in such a case they pro vide the best soundproofing across the entire length of the building element.

The support structures advantageously support the layers of sand from the side, because this means that the manufacture of the building element is simple.

The outermost opposite support structures of the building element are advantageously located at the sides of the building element, because they, being hard elements compared to building foam, protect the sides of the building ele ments against impacts.

Advantageously the support structures of the building element extend from the first edge surface of the building element to the other edge surface be cause then they stiffen the building element along its entire length.

The grain size of the sand in the sand layers is advantageously 0 to 4 mm, because this provides a good soundproofing property. If the grain size is big and over 4 mm, the soundproofing property weakens.

The bottom part of the building element advantageously comprises a bottom board, whereby the bottom surfaces of the support structures are arranged at a distance from the top surface of the bottom board by means of building foam. The bottom board makes the building element better to handle at its usage location by reducing the risk of it getting damaged during installation, for example. In addi tion, the bottom board may act as a ceiling in case the building element is an intermediate floor element or a roof element. The building foam dampens sound transmission from the bottom board to the support structures.

The combined width of the layers of sand is advantageously 50 to 90% of the width of the building element. This establishes efficient soundproofing against impacts.

Preferred embodiments of the invention are disclosed in the dependent claims.

A big benefit of the inventive building element is that is it capable of very effectively dampening sound originating from different sources of sound. In particular, it provides good soundproofing against structure-borne noise such as knocking caused by impacts, but additionally provides good soundproofing against airborne noise. In addition, it provides good thermal insulation. Furthermore, it is easy to manufacture industrially. A further benefit of the building element is that due to the layers of sand it is not lightweight. It is often an advantage that building elements are not very light; the weight of building elements stabilizes a struc ture/building implemented with elements.

Brief description of the drawings

The invention will now be described in greater detail by means of ex amples and with reference to the attached drawing, in which:

Figure 1 is a perspective view of the inventive building element,

Figure 2 shows a scaled-down (by 50% in relation to Figure 1) bottom of the building element of Figure 1,

Figure 3 shows a support structure used in the building element of Fig ure 1,

Figure 4 is a perspective view of a second embodiment of the inventive building element,

Figure 5 shows a scaled-down (by 50% in relation to Figure 4) bottom of the building element of Figure 4, and

Figure 6 shows a support structure used in the building element of Fig ure 4.

Detailed description of the invention

Figure 1 shows a rectangular building element 1 according to the inven tion, which may be used in buildings as an intermediate floor element or base floor element. The length of the building element 1 is preferably 5 to 10 m, the width is preferably 2 to 3.5 m, and the height (thickness) is preferably 0.3 to 1 m. The interior of the building element 1 has building foam 8a in it, acting as heat insulation and binds the structure uniform. The building element 1 prefer ably has no other heat insulation than building foam 8a, whereby this forms the single heat insulation of the building element, and there is no other heat insulation such as construction wool, for example. As building foam 8a, polystyrene or polyu rethane may preferably be used. The interior is covered by a surface board 10, which forms a first facing surface 2 of the building element 1. Preferably, the sur face board 10 is a multilayer, typically a three-layer, building element made of crosswise glued conifer chips. Such a board is at times referred to as an OSB board. Instead of an OSB board, the board may be an MFD board (medium-density fibre board), or another compact-grained building board. A board is not necessarily needed at the bottom of the building element 1, whereby the second facing surface 3 is formed by the bottom surfaces of the support structures 9 in addition to the building foam surfaces. Reference number 9 denotes a longitudinal support struc ture in the building element 1, which extends from a first edge surface 4 of the building element to the opposite edge surface of the building element (see, refer ence number 5 in Figure 2). There is a plurality of adjacent support structures 9 at a distance L2 from each other, and they are bound to each other with building foam 8a. Building foam 8a thus acts as a binding agent. The distance L2 is 300 to 600 mm and the support structures 9 are arranged rectilinearly. The quantity of support structures 9 depends on the size of the building element 1. In case the building el ement 1 is 2 to 3.5 m wide, the quantity of support structures is 5 to 10. The oppo site longitudinal flanks of the building element 1, that is, at the edges 6, 7 there are supports 9 which protect the edge surfaces against potential impacts when the building element is being handled and installed in place.

Top surfaces 11 of the support structures 9 are arranged at a distance LI from the bottom surface of the surface board 10 of the building element. This is important so that impacts and sounds directed onto the surface board 1 would not be carried onto the supports 9, and through the supports to the bottom of the build ing element 1. The distance LI is preferably 20 to 40 mm, so the height of the sup port structures 9 is 20 to 40 mm less than the height of the building element 1. Between the bottom surface of the surface board 10 and the top surface 11 of the support structures 9 there is building foam 8a.

The support structures 9 are preferably wooden. They may be solid wood, as shown in Figure 3, or wood-like material (building, plywood, OSB, or similar board). They may be lattice structures as illustrated in Figure 5. The width of the support structures 9 is 9 to 70 mm, preferably 30 to 50 mm.

Reference number 8b denotes the layers of sand between the support structures 9. The layers of sand 8b are in the lateral direction supported to the sup ports 9, and preferably extend continuously from the first edge surface 4 or first edge of the building element 1 to the opposite second edge surface 5 or second edge. The first edge and the opposite second edge of the building element 1 may have supports for the layers of sand 8b, and then these layers of sand more specif ically extend from the first edge of the building element to the second opposite sec ond edge of the building element. As shown in the figure, the layers of sand 8b ex tend on the entire width of the building element 1 - obviously excluding the width taken up by the support structures 9, whereby the combined width of the layers of sand is 50 to 90%, and more preferably 70 to 90%, of the width of the building element 1. The layers of sand 8b are important in that they effectively dampen impact noise transmitted from the top surface of the building element 1 to its bot tom surface. The layers of sand 8b dampen such sounds far more effectively than building foam 8a. Under the layers of sand 8b, there is building foam 8a which sup ports the layers of sand. Over the layers of sand 8b, there is also building foam 8a. The thickness of the building foam 8a covering the layers of sand 8b is 20 to 50% of the thickness of the building element 1. The thickness, in other words the height, of the layers of sand 8b is preferably 60 to 100 mm, but the thickness range may be wider than this, such as 30 to 120 mm. It is obvious that the thicker the layers of sand 8b are, the more effectively they dampen sound. Even though good sound proofing is desirable, very thick layers of sand make the building elements 1 heavy, which is not always desirable.

The grain size of the sand used in the layers of sand 8b is 0 to 4 mm. Due to the fact that the range of grain size includes sand with a very small grain size (0 to 1 mm), the sound dampening property of such sand is excellent. The grain size of the sand may also be 0 to 16 mm, but the dampening property of such sand is not as good as that of sand with the grain size of 0 to 4 mm. The sand in the layers of sand 8b is in flowable form, that is, the grains of sand are noth ound to each other, because sand in flowable form is particularly good for sound dampening.

In the building element 1 of Figure 1, there are no major air spaces be tween the facing surfaces 2 and 3, because building foam 8a acts as a substance filling the structure with the purpose of binding the structure uniform. Figure 4 shows an inventive building element 1’ which differs from the building element 1 of Figure 1 in that its bottom part comprises a bottom board 12’. The bottom board 12’ may be a plywood board or an OSB board. In addition, bottom surfaces 16’ of support structures 9’ are arranged at a distance L3’ from the top surface of the bottom board 12’ by means of building foam 8a’. The distance L3’ is preferably 20 to 50 mm. Figure 4 uses corresponding reference numbers as Fig ure 1 for the corresponding components. The building element 1’ of Figure 4 uses the support structure 9’ shown in Figure 6, which is a lattice support structure. The benefit of the lattice support structure 9’ is that due to its openings it may allow the layers of sand 8b to be accomplished faster (when the building element is being manufactured); in addition, the manufacture of the lattice support structure 9’ does not require as much wood as manufacturing the support structure 9 according to Figure 3. Furthermore, if the building element 1’ comprises lattice support struc tures 9’, the height of the building element 1’ may be smaller than in such a case where the support structure is of solid wood instead of a lattice support structure, because the height of the layer of sand 8b may be smaller. Alternatively, in the em bodiment of Figure 4, it is naturally possible to use the support structure according to Figure 3.

Under the bottom board 12’ there is a base board 13’, attached by means of battening to the bottom board. The base board 13’ is typically a trim panel and may be a plaster board, for example. The battening comprises a plurality of longi tudinal supports 14’, which are rectilinear with the support structures 9’. The sup ports 14’ are preferably of wood, or they may be made of metal profile. As shown in Figure 4, the supports 14’ preferably align with the support structure 9’, as ex amined in the vertical direction, because this is advantageous in the strength tech nical sense for the building element 1. The supports 14’ arranged in said manner and the base board 13’ form a plurality of installation channels 15’, which extend from the first edge surface 4’ of the building element 1’ to the second edge surface 5’ of the building element . The installation channels 15’ are for electric wires, fibre optical cables, and suchlike.

The building elements 1, 1’ of Figures 1 and 4 preferably have end boards (not shown), which prevent the sand from flowing out of the edge surfaces 4, 5; 4’, 5’ of the building element.

The manufacturing method of the inventive building element is not de scribed in detail here, because the manufacture thereof will not present problems to a person skilled in the art. In the following, only a brief description of the manufacture of the building element 1 will only be offered. The manufacture may essentially take place so that a surface board 10 of the building element is placed on a platform, such as a floor, after which building foam is sprayed over it. This means that the surface board 10 is upside down during manufacturing, so turned opposite to that shown in Figure 1. The amount of sprayed building foam is such that once the foam has expanded and hardened, the foam height is at least approx imately 50 mm, which is to say that the height exceeds the aforementioned distance LI. The support structures 9 must be arranged at the distance LI from the surface board 10 before the foam hardens. After the hardened foam surrounds the bottom ends of the support structures 9, sand is dumped on the foam. The sand quantity is so chosen that the layers of sand 8b are as high as desired. Then, building foam is sprayed on the layers of sand 8b to the extend that the building foam, after hard ening, rises to match the height of the support structures 9. The amount of building foam that exceeds the supports structures 9, is cut off so that a planar facing surface 3 is created for the building element 1, cf. Figure 2 (showing a view towards the planar facing surface 3 of the building element 1). Also the hardened building foam that possibly exceeds the edge surfaces 6, 7 defined by the support structures 9 at the edges of the building element 1, that is, outside (unless there is arranged a bar rier for the building foam not to flow over the edge surfaces), is cut off. The same applies to the building foam that pushes its way outside the edge surfaces 4 and 5. When a building element manufactured this way is turned upside down, a building element of Figure 2 is obtained, that is, a building element in its use position. One and the same building element may have both polystyrene and polyurethane, in which case polystyrene is placed where the highest loading occurs. This is rela tively simple to arrange in practise by changing the sprayed substance between the aforementioned different work stages of the building board.

In the above, the invention is described by means of examples, only, and it is for this reason pointed out that the building element 1, 1’ according to the in vention may as concerns its details be achieved in various ways within the scope of the attached claims. Consequently, the number and geometry of the support struc tures 9, 9’ may vary; the precise location of the layers of sand 8b, 8b’ in the building element 1 may vary, the material of the surface board 10 may differ from the de scribed, etc. Instead of polystyrene and polyurethane, a similar pourable substance may act as the building foam 8a.