GB2226580A - Lintel - Google Patents

Abstract

A lintel is formed of two parts 2, 4 interconnected to form a downwardly open channel with horizontal flanges 6, 24 to support respectively the outer and inner skins of a cavity wall. The inner skin side (which supports the greater load) is stiffened by ribs 28 extending down the vertical face 16 and at least partly across the flange 24. Stiffening blocks 30 may be located at spaced intervals along the channel by the ribs 28 and the remainder of the channel filled with insulation foam 44. Also disclosed is a lintel as in figure 3 but without the ribs 28, the channel being filled with a structural foam which may be denser nearer the bottom than the top. <IMAGE>

Description

cxvre WALL LINTLS This invention relates to lintels for use in cavity walls.

A known cavity wall lintel comprises a flange of material to support the inner skin of the wall, a flange of material to support the outer skin of the wall and a generally rectangular channel connecting the two flanges and, in use, protruding upwards into the cavity. The inner flange of the lintel has to support a greater weight than the outer flange since the floors of a building are usually keyed into the inner skins of the walls. Typically the ratio of inner flange load to outer flange load is of the order of 3:1. This normally either necessitates the use of thicker material for the inner flange, or the use of material with a greater stress rating than the outer flange which usually increases the weight and cost of the lintel.

The object of the present invention is to provide an improved lintel which enables more cost-effective use to be made of the materials used in its construction.

The present invention is defined in its various aspects in the appended claims to which reference should now be made.

The invention will now be described in more detail by way of example with reference to the drawings in which: Figure 1 is a cross section through a first lintel embodying a first aspect of the invention; Figure 2 is a cross section through a second lintel embodying the first aspect of the invention; Figure 3 is a cross section through a third lintel embodying the first and second aspect of the invention; and Figure 4 is a sectional side elevation of a portion of the inner leaf of a lintel embodying the first and second aspects of the invention.

The lintel of Figure 1 has an outer leaf 2 to support the outer skin of a cavity wall and an inner leaf 4 to support the inner skin. The outer leaf has a horizontal portion or flange 6 upon which the outer skin of the wall rests. This horizontal portion has a water drip 8 to prevent rain water from running along the underside of the lintel back towards the building.

The outer leaf has a vertical portion 10 which extends upwards into the wall cavity close to the inside of the outer skin of the wall. A roof portion 12 of the outer leaf bridges the gap between the outer leaf 2 and inner leaf 4. A further vertical portion 14 of the outer leaf, connected to the roof portion 12 lies adjacent to a vertical portion 16 of the inner leaf. The two vertical portions 14, 16 are held together by connectors 18 thus holding the inner and outer leaves together. The connectors 18 can be either self piercing rivets, standard rivets, nuts and bolts, resistance spot welds, plug welds or seam welds as appropriate.

An insulating strip 20 of, for example, PVC can be provided between the vertical portions 14, 16 of the outer and inner leaves. This acts as a thermal break in between the outer and inner leaves, thus reducing heat conduction across the wall cavity. This plastic strip also forms a seal between the inner and outer leaves of the lintel and prevents water fram entering the lintel from the wall cavity. It also prevents any possible corrosion due to bimetallic contact between the inner and outer leaves when they are formed from different materials.

This insulating strip 20 can also be extended upwards and be made of suitable material to form a flexible damp proof membrane which together with the outer ocoponent of the lintel can provide a damp proof course.

The flexible damp proof membrane can be built into the blocIwork coursing to suit.

A further portion 22 of the inner leaf is turned over the vertical portion 14 of the outer leaf, as shown in Figure 1.

This overlapping portion adds rigidity to the lintel as a whole.

This turned over portion 22 provides a useful hand grip to lift the lintel during fabrication, storage and erection, and also provides an anchorage point for a hoist sling for longer, heavier lintels.

The vertical portion 16 of the inner leaf 4 extends downwards from the connectors 18 and there is a horizontal portion or flange 24 extending away from the cavity for supporting the inner skin of the wall. This horizontal portion 24 is in substantially the sane plane as the horizontal portion 6 of the outer leaf.

The e respective vertical portions 10, 16 of the outer and inner leaves of the lintel and the roof portion 12 of the outer leaf form a channel 26 which, in use, extends into the wall cavity.

The inner leaf 4 shown in Figure 3 includes at least one stiffening swage 28 which extends, from the junction 46 between the horizontal portion 24 and the vertical portion 16 of the inner leaf, at least partially across the horizontal portion 24 and at least partially up the vertical portion 16.

The number of stiffening swages included in a particular lintel will vary according to the design load and length of the lintel. These swages 28 increase the stiffness of the inner leaf and reduce the amount of deflection of the section.

Adjacent to each swage 28 in Figure 3 and within the channel 26 is a structural block 30 which bridges the channel 26.

These blocks 30 may be sufficiently narrow to fit within the recesses formed by the swages. This is illustrated in the sectioned side elevation of Figure 4. This fit within the recess helps to prevent lateral movement of the blocks. This further increases the stiffness of the lintel by preventing the loads on the inner and outer leaves from forcing the inner and outer leaves towards each other. This block is formed from a suitable structural material such as wood, steel or structural rubber and may be held in place by a mechanical fixing such as nails, screws, rivets, welding, punched lugs on the inner and outer leaves, or by using an adhesive as appropriate. However it may be sufficient for the blocks to spring the leaves 2 and 4 apart and simply be gripped therebetween.When the lintel is under load the gripping pressure is increased as a result of the loading of the flanges 6 and 24.

The blocks may be provided in lintels with and without swages since their action is the same in each case.

The gaps between the blocks 30 (along the length of the lintel) may be filled with insulating material 40 and 44 to increase the effectiveness of the lintel as a thermal barrier.

This filling can be of various materials including expanded polystyrene, rock wool, glass wool, polyisocyanurate foam, phenolic foam, and rigid polyurethane foam. Sane of these materials have good compressive strength and will, together with the blocks 30, increase the stiffness of the lintel.

The insulation material may be in sections 40 placed between the blocks 30 or, in the case of structural foams 44 may be poured into the base of the cavity 26 and fill the cavity up as the material foams. Structural foams applied in this manner will bond to the vertical portions 10 and 16 as well as to the roof portion 12 as they foam. These foams may include fibre reinforcement. These structural foams typically have good mechanical properties and compressive strength and will add to the torsional stiffness of the lintel.

The foam may have a varying density with the most dense foam being near the base of the lintel where the highest compressive strength is required and the least dense being above the dense portion providing improved insulation properties.

A further stiffening rib 32 is shown and this extends along the length of the lintel near to the inner edge of the inner flange 24. This rib 32 helps to reduce the deflection of the portion 24 of the inner leaf furthest from the wall cavity.

The underside of the inner flange 24 as shown in Figure 1 will usually have a plaster coat applied to it after installation.

This forms a substrate (or decorative finish) as well as protecting the metal of the lintel from the effects of fire.

To provide a key for the plaster, a lath 34 is provided which may be crimped with an edge strip 48 to the inner leaf and is welded, bonded or mechanically fixed to the inner leaf portion 24. This lath could be produced from expanded metal or plastics or soma other suitable material. This may be in mesh, grid or textured form.

Because the inner and outer leaves are separate, different materials can be used in their manufacture. Generally the outer leaf carries a much lighter load than the inner leaf and can be made of thinner material or material with a lower stress rating than the inner leaf. However, the outer leaf is exposed to the atmosphere and is therefore often made from a more durable material than the inner leaf. For example, it could be made from post-galvanised or stainless steel with the inner leaf made from pre-galvanised steel. Alternatively both leaves could be made from the same material.

The lintel shown in Figure 2 may be used with heavier loads or longer spans than the lintel of Figure 1. To increase the strength of the lintel, a structural steel sheet 36 which may be perforated connects portions 6, and 24. This may extend along portion 6 and may extend to the far edge of portion 24.

This steel sheet may be used instead of the lath 34 as shown or in conjunction with a lath fixed to portion 24 and the steel sheet when the steel sheet does not extend to the edge of portion 24. This structural steel sheet may be discontinuous along the length of the lintel to reduce the quantity of steel required and the weight of the lintel.

This can be formed from pre-galvanised steel, post-galvanised steel or stainless steel and is fixed to the inner and outer leaves of the lintel by welding or by rivets 38.

A layer of insulation such as PVC may be provided between the perforated steel sheet 36 and the inner and outer leaves of the lintel to further increase the effectiveness of the lintel as a thermal barrier.

Figure 3 shows a lintel in which the plaster lath is formed fram a sprayed on coating 42. This coating 42 may comprise a foam or some form of plastics cement. The coating is shown in Figure 3 as extending across the blocks 30 in the channel but it may also be applied before the blocks are inserted into the channel.

Coating 42 may be preformed and attached to an adhesive strip.

Figure 4 shows a sectional side view of a lintel in which a stiffening swage 28 can be seen extending up the vertical portion 16 of the inner leaf and also into the horizontal portion 24.

Because the inner and outer leaves are separate components, a number of different widths of cavity and thicknesses of wall skin can be accommDdated with a small number of components, thus reducing the quantity of components that need to be manufactured and stocked. For example, four different inner and four different outer components would enable a range of sixteen different lintels to be made.

The turned over portion 22 of Figures 1, 2 and 3 may only be necessary when the lintel is subjected to severe lateral budding forces. When this is not the case, the inner and outer leaves can both terminate vertically at the same point if appropriate with the optional plastic on PVC strip forming an effective seal between them.

Where a lintel is to be installed close to the eaves of a building, the width of the horizontal portion 6 or the outer leaf can be significantly reduced to say half the width of the outer skin of the wall since it only carries load from the inner skin. The water drip 8 can also be omitted.

Claims (20)

1. A lintel for supporting the inner and outer skins of a cavity wall oomprising inner and outer leaves of material, each having, a horizontal portion for supporting the respective inner and outer skins of the wall, and a substantially vertical portion extending, in use, upwards into the cavity, at least one substantially vertical portion having a portion extending across the cavity and fixed to the other leaf, thereby forming a channel within the cavity, the inner leaf having at least one stiffening swage extending from the channel at least partially across its horizontal portion and at least partially up the channel wall formed by its vertical portion.

2. A lintel for supporting inner and outer skins of a cavity wall comprising inner and outer leaves of material, each having, a horizontal portion for supporting the resepctive inner and outer skins of the wall, and a substantially vertical portion extending, in use, upwards into the cavity, at least one substantially vertical portion having a portion extending across the cavity and fixed to the other leaf, thereby forming a channel within the cavity, the channel being at least partially filled with a structural foam.

3. A lintel according to claim 1 including a block within the channel adjacent to the or each stiffening swage and in abutment with both substantially vertical portions.

4. A lintel according to claim 3 in which the block fits within a recess formed by the stiffening swage.

5. A lintel according to claim 1 including a structural foam at least partially filling the channel.

6. A lintel according to claim 1, 2, 3, 4, or 5 including a lath extending across the underside of the horizontal portion of the inner leaf and at least partially across the channel and fixed to at least the inner leaf.

7. A lintel according to claim 6 in which the lath comprises a sprayed on plastics material.

8. A lintel according to claim 6 in which the lath comprises a plastics material attached to the lintel by a adhesive strip.

9. A lintel according to claims 1, 2, 3, 4, or 5 including a metal sheet extending at least partially across the underside of the horizontal portion of the inner leaf, across the channel and at least partially across the underside of the horizontal portion of the outer leaf and fixed to both the inner and outer leaves.

10. A lintel according to claim 9 in which the metal sheet is discontinuous along the length of the lintel.

11. A lintel according to claim 9 or 10 including a lath attached to both the inner leaf and to the metal sheet.

12. A lintel according to claim 9, 10 or 11 including a layer of insulating material between the metal sheet and the inner and outer leaves.

13. A lintel according to any of claims 1 to 12 including a stiffening rib extending along the distal edge of the horizontal portion of the inner leaf and parallel to the channel.

14. A lintel acoording to any of claims 1 to 13, in which at least one of the leaves includes a portion turned over the other leaf near to the fixing between the two leaves.

15. A lintel according to any preceding claim including a layer of insulating material between the inner and outer leaves where they are fixed together.

16. A lintel according to claim 15 in which the layer of insulating material is extended upwards to form a flexible damp proof membrane for building into blockwork above the lintel.

17. A lintel according to any preceding claim in which gaps in the channel are filled with thermally insulating material.

18. A lintel substantially as herein described with reference to Figure 1 of the drawings.

19. A lintel substantially as herein described with reference to Figure 2 of the drawings.

20. A lintel substantially as herein described with reference to Figure 3 of the drawings.