GB2318368A

GB2318368A - Cavity wall lintels

Info

Publication number: GB2318368A
Application number: GB9621479A
Authority: GB
Inventors: Thomas John William Burge
Original assignee: I G Ltd
Current assignee: I G Ltd
Priority date: 1996-10-15
Filing date: 1996-10-15
Publication date: 1998-04-22
Also published as: GB9621479D0

Abstract

A cavity wall lintel (20) has two base flanges (26, 28) joined by a portion projecting upwardly within the cavity (14). The lintel consists of two structural members (22, 24), each of which is a simple section of steel or a composite material, having a vertical flange (30, 32). The vertical flanges are joined together through a body of thermal insulation (36) which may be adhesively secured directly to them.

Description

CAVITY WALL LINTELS This invention relates to lintels for spanning an opening in a cavity wall, the lintel having a load-bearing structure which comprises a pair of base flanges projecting away from each other, with each base flange being joined along its inner edge, i.e. the edge nearest to the cavity and to the other flange, to an upright element, which is usually integral with the flange.

In the load-bearing structure of such lintels as currently made, which is typically of steel, the two upright elements are spaced apart with thermal insulation between them. The lintel thus has an upstanding central portion, comprising the insulation flanked by the upright elements. This central portion is inserted within the cavity, the two base flanges being supported at their ends in the respective leaves of the wall.

One simple form of currently-used lintel consists of an upright channel section, open at the bottom and with the base flanges projecting on either side of its open end, the channel being filled with insulation.

More complex forms of this component may be fabricated from more than one steel section, these sections being joined directly to each other, typically by welding. In these known lintels the channel section has a base section, or more strictly a roof, which joins the upright elements together.

According to the invention, in a lintel for spanning an opening in a cavity wall, having a load-bearing structure comprising a pair of base flanges projecting away from each other, with an upright element joined to each base flange along the edge of the latter nearest to the other base flange, and a thermal insulating body between the upright elements, each base flange and its associated upright element together constitute a separate member, the two structural members being joined together through the insulating body.

Thus the load-bearing structure is in two parts, which are not joined directly to each other, and each of these parts can be made with only enough material to satisfy the load bearing requirements. In addition, the number of standard metal components required can be reduced in a lintel according to the invention. For example, lintels for use with cavities of various widths can use the same steel components, the cavity width determining the transverse width of the insulation between these components.

Different designs of inner and outer steel components (i.e. for the inner and outer leaves of the wall) can be used in conjunction with each other in the same lintel, instead of each combination of these different designs requiring to be made, and stocked if necessary. This gives greatly enhanced flexibility of lintel design with a small number of simple standard components, so enabling the number of available lintel cross-sections to be increased while leading to a substantial reduction in warehousing costs, as well as potentially reducing manufacturing costs.

In general, the structural members of the lintel are of simple cross section. They may be made of a suitable metal, such as steel, which can be relatively thin. Alternatively, they may be of suitable composite materials such as glass reinforced plastics or fibre reinforced plastics. In a given lintel according to the invention, these two separate parts of the load-bearing structure may indeed be of different materials.

The body of insulation can take any desired form. It may for example be applied as a liquid foam to the two structural members held in a suitable jig. Typical materials for such a foam are polyurethane or phenolic resin, which either adhere directly to the facing surfaces of the upright elements (which in practice take the form of vertical flanges). Alternatively, the insulation may be in the form of blocks of insulating material, such as preformed foam blocks which can be attached to the vertical flanges with an adhesive. Alternatively again, the insulating material may be enclosed in an envelope or casing of a suitable material (which can for example be filled with the insulating material in liquid form, the latter then being cured to form a solid mass), to form an insulating body of the required shape and dimensions. These insulating bodies can be attached to the two structural members either adhesively or by suitable mechanical means.

It is desirable for the two load-bearing structural components to be joined together (through the insulation, according to the invention) for purposes of storage and transport, i.e. until the lintel is installed in a building. Thereafter, the joint between the insulating component of the lintel and the vertical flanges serves merely to hold the insulation Some preferred embodiments of the invention will be described below, by way of example only and with reference to the accompanying drawings, in which: Figure 1 is a cross section through one lintel according to the invention; and Figures 2 and 3 are similar cross sections showing further embodiments.

In Figure 1, a cavity wall has an outer leaf 10, an inner leaf 12, and a cavity 14 between them. This wall, shown in phantom lines, is conventional. A door opening 16, containing a door frame 18, is formed through the wall and is spanned by a cavity wall lintel 20.

The lintel 20 comprises two thin steel load-bearing structural members, namely an outer member 22 and an inner member 24.

Each of these members consists essentially of a simple angle section comprising a horizontal base flange 26, 28 and an upright element consisting of a vertical flange 30, 32 respectively. Each vertical flange is joined to the associated base flange along the edge of the latter that lies (in the cavity 14 in Figure 1) closest to the other base flange. The flange 26 has the usual downward lip 34 on its outer edge.

The members 22 and 24 are joined together through a body of thermal insulation 36, and in this example it is the body 36 itself that joins them together. The body 36 consists of polyurethane or phenolic resin foam poured into the preset gap between the vertical flanges 30 and 32 (in a suitable jig) and then cured. Alternatively, the body 36 may consist of preformed foam blocks (e.g. of these same materials), attached to the flanges 30, 32 by a suitable adhesive. The body 36 may be interrupted at suitable intervals in the usual way by timber inserts.

A conventional plaster key 38 is provided along the exposed bottom edge of the insulation body 36, and the underside of the inner flange 28 also has a plaster key 40. Figure 1 shows, purely by way of illustration, a plaster key 40 in the form of an added component, such as expanded mesh.

In Figure 2, the insulating body is in the form of one or more preformed blocks 50, comprising an envelope 52 preformed to shape and containing a mass of thermal insulating material 54.

Figure 2 also illustrates another method of attaching insulating blocks (of any kind) to the structural members 22 and 24, namely by means of light rivets 56. This is only one possible mechanical method of attaching the insulation to the structural members. The use of adhesives may be omitted if such mechanical methods are used.

Similar blocks 50 are used in the lintel shown in Figure 3, but in this case they are secured adhesively to the vertical flanges 30 and 32.

Figures 2 and 3 also illustrate the fact that the invention is applicable to lintels of heavier duty types, in which the inner structural member 24 is of channel section having an upper flange 60. In Figure 3, the vertical flange 30 of the outer member 22 is extended by an inclined portion 62 to give additional strength.

Figures 2 and 3 also show examples of other forms of plaster key, namely indented slots 64 in Figure 2, formed here in the flange 28 and in the base of the envelope 52; and in Figure 3, the same plaster key that bridges the cavity in Figure 1 is extended across the flange 28.

In each case the lintel is installed once both leaves of the wall have been raised to the same level, so that the ends of the two base flanges 26 and 28 can be set into the respective leaves 10 and 1 2 of the wall on either side of the door opening 1 6. A dampproof course 66 is laid over the flange 26 so as to overlie the top of the insulating body 36 if required, and building of the wall is then continued upwards in the usual way.

It will be noted that the top of the insulating body is inclined to the vertical in the examples shown, so that the two vertical flanges are of different heights. If desired, the latter may be of the same height; and the top surface of the insulating body can have any suitable shape.

Claims

1. A lintel for spanning an opening in a cavity wall, having a loadbearing structure comprising a pair of base flanges projecting away from each other, with an upright element joined to each base flange along the edge of the latter nearest to the other base flange, and a thermal insulating body between the upright elements, wherein each base flange and its associated upright element together constitute a separate structural member, the two structural members being joined together through the insulating body.

2. A lintel according to Claim 1, wherein the structural members are joined together by the insulating body.

3. A lintel according to Claim 1 or Claim 2, wherein the insulating body is adhesively attached to the upright elements.

4. A lintel according to any one of Claims 1 to 3, wherein the insulating body is in the form of at least one preformed block.

5. A lintel according to Claim 4, wherein the preformed block comprises an envelope containing thermal insulating material.

6. A lintel according to any one of Claims 1 to 3, wherein the insulating body is formed from a mass of liquid polyurethane or phenolic resin foam adhering directly to the upright elements.

7. A lintel according to any one of the preceding Claims, wherein at least one of the structural members is made from a material selected from a metal, an alloy, a glass reinforced plastics material, a fibre reinforced plastics material.

8. A lintel according to any one of the preceding Claims, wherein the two structural members are of different materials.

9. A lintel substantially as described in the foregoing description with reference to any one of Figures 1 to 3 of the accompanying drawings.