GB2193516A

GB2193516A - Damp proof strips or cavity trays with flashing attachment

Info

Publication number: GB2193516A
Application number: GB08715990A
Authority: GB
Inventors: Anthony Victor Custerson
Original assignee: Timloc Building Products Ltd
Current assignee: Timloc Building Products Ltd
Priority date: 1986-08-06
Filing date: 1987-07-07
Publication date: 1988-02-10
Anticipated expiration: 2007-07-07
Also published as: GB2193516B; GB8715990D0; GB8619209D0

Abstract

A cavity tray for building into the outer skin of a cavity wall is formed as a single integral injection moulding and comprises a base portion 1, arear wall 2, an end wall 4 and a gully 5 in the base portion 1 adjacent the rear wall 2. To facilitate the fastening of a strip of lead flashing to the front edge of the base portion 1. the base portion 1 has an upwardly stepped portion 7 and a downwardly projecting flange 9 which is connected to it by an integrally formed hinge 10 of the plastics material. The flange 9 is provided with spaced projections 11 which pass through perforations in the flashing and into apertures 8 in the stepped portion 7. To lock the flashing strip in position, the tips of the projections 11 may then be heated to melt them and form buttons on their ends so that they cannot pass back through the apertures 8. <IMAGE>

Description

SPECIFICATION Damp proof strips or cavity trays for forming damp proof courses in walls This invention relates to damp proof strips or cavity trays for building into brickwork or blockwork cavity walls to form a damp proof course which extends through the outer skin and across the cavity of the wall.

When a horizontal damp proof course is required extending along a single joint between two adjacent courses of the outer skin of the wall, a damp proof strip of indefinite length maybe used. When, however, a stepped damp proof course is required, for example where a pitched roof abuts the outside of the wall, individual cavity trays are used in the joints between successive courses of the brickwork or blockwork and these cavity trays also include an upright wall at one end forming a vertical damp proof course between adjacent trays which are built into the wall in such a way that they overlap each other.

With either such damp proof strips or cavity trays, a lead flashing is frequently required extending downwards from the damp proof course. Where the damp proof course is horizontal, it has been usual to fix the flashing by raking out the horizontal joint of the brickwork along the damp proof course and after this the edge of the flashing is inserted into the joint and is held in position with newly applied mortar. With cavity trays on the other hand, individual strips of lead flashing are necessary for each tray and it has been the usual practice to fix one edge of the strip of flashing to the front edge of the cavity tray by means of staples before the cavity tray is built into the brickwork or blockwork.Frequently the flashing strips are stapled to the cavity trays in the factory where the cavity trays are manufactured, but this greatly increases the difficulty of packing the trays and there is also a tendency for the flashing strips to be damaged or to become partly detached from the cavity trays before the cavity trays are fixed in position in the wall.

As an alternative the flashing strips may be fitted in situ. To do this, after the cavity trays have been built into the wall, the mortar in the joints beneath the front edges of the trays is raked out, the edges of the flashing strips are inserted under the trays and lead wedges are inserted over the trays to press the trays down over the flashing strips. This method is, however, labour intensive and therefore expensive.

The object of the present invention is to provide a damp proof strip or cavity tray to which a lead flashing strip maybe fixed in a very simple manner on site without the use of any extraneous fixings so that it is made much easier to ensure that the flashing strip is fixed to the damp proof strip or cavity tray in a satisfactory manner at appropriate intervals.

To this end, according to this invention, a damp proof strip or cavity tray as initially described is injection moulded from resilient thermo-plastic plastics material and comprises a base portion for building into a horizontal joint of the outer skin of the wall, a cavity portion projecting from the rear edge of the base portion for bridging the cavity and an integrally formed clip portion for fixing a strip of flashing to the front edge of the base portion, the clip portion comprising a flange extending along and projecting upwards or downwards from near the front edge of the base portion to which it is connected by an integral hinge of the plastics material, and projections and corresponding apertures along the flange and along the front edge of the base portion, either the projections being on the flange and the apertures in the base portion or vice versa, the arrangement being such that when a strip of flashing having perforations at the same spacing as the projections and apertures is placed along the front edge of the base portion and the flange is folded about its hinge towards the base portion, the edge of the flashing is sandwiched between the flange and the front edge part of the base portion with the projections extending through the perforations and through the apertures to fix the flashing to the damp proof strip or cavity tray.

If the flange projects upwardly from the base portion, the projections preferably project upwards from the base portion and the apertures are provided in the flange. In this case the flashing is placed over the top of the front part of the base portion with the projections extending through its perforations and the flange is then folded down over the edge of the flashing so that the projections extend through its apertures in which they are preferably a snap fit.

If, as is at present preferred, the flange projects downwardly from the base portion, the projections are preferably provided on the flange and the apertures are in the base portion. In this case the edge of the flashing is placed under the base portion with its perforations in register with the apertures and the flange is then bent up so that its projections pass through both the perforations and the apertures.

In either case, when the flange has been bent upwards or downwards to sandwich the edge of the flashing in position until the projections have passed through the apertures, the tips of the projections may be heated, for example by a hot tool, to expand them and, if required, weld them in position.

The flange is preferably continuous along the length of the base portion, but it may alternatively be divided into a series of spaced apart tabs each of which is provided with one or more projections or apertures.

The damp proof strip or cavity tray may be injection moulded out of any thermo-plastic plastics material which is suitable for use as a damp course and the hinge can then still be integrally formed of the plastics material because the hinge only has to be flexed one to sandwich the flashing in position. Preferably, however, the thermo-plastic plastics material is a polyolefin and the preferred material, which is particularly durable and particularly suitable for forming the hinge is polypropylene.

In the case of a cavity tray, a rear wall portion may be provided extending directly upwards, or upwards and rearwards from the rear edge of the base portion and in this case the rear wall portion forms the cavity portion and, in use, extends across the cavity of the wall into contact with the outer face of the inner skin of the wall.

The cavity tray may also be provided with an end wall at one end of the base portion and this end wall is joined integrally to the base portion and to the rear wall portion forming a box-like corner at that end of the tray. In use, in order to form a stepped damp proof course, adjacent trays are placed in adjacent horizontal joints of the brickwork or blockwork and the free end of the upper tray extends over the end wall of the lower tray.

Any moisture which then enters the cavity then runs off the upper tray into the lower tray and so on along the length of the stepped damp proof course. The tray may then be provided with a gully at the junction between the base portion and the rear wall and the end wall is provided with a recess to receive the end of the gully of the tray which overlaps it.

An example of a cavity tray and an example of a damp proof strip in accordance with the invention are illustrated in the accompanying drawings in which: Figure 1 is a perspective view of the cavity tray; Figure 2 is a cross-section through the cavity tray as seen in the direction of the arrows on the line ll-ll in Fig. 1; Figure 3 is a cross-section similar to Fig. 2, but showing the cavity tray built into a cavity brick wall and with a strip of lead flashing attached to the front edge of the base portion of the tray; and, Figure 4 is a cross-section through the damp proof strip.

The cavity tray shown in Figs. 1 to 3 of the drawings is formed as a single integral injection moulding of polyproplyene and comprises a base portidn 1, a rear wall 2, which extends upwardly and rearwardly from the rear edge of the base portion and has an upright seating portion 3 along its upper edge, and an end wall 4. Although this is not shown, the base portion 1 may be moulded with a pattern of ribs on its under surface with corresponding depressions in its upper surface to form a key with mortar in which, in use, it is embedded.

A gully 5 of V-shaped cross-section is formed near the rear edge of the base portion 1. The end wall 4 is provided with a V-shaped recess 6 into which the end of the gully 5 of an adjacent cavity tray in the joint between a higher course of bricks fits when the cavity tray is positioned in a wall.

The base portion 1 has at its front edge an upwardly stepped portion 7 provided along its length with a series of equally spaced apertures 8. A downwardly projecting flange 9 is connected to the base portion 1 adjacent the rear edge of the stepped portion 7 by a hinge 10. The flange 9 has a series of stud-like projections 11 at the same spacing as the apertures 8 and in register with the apertures 8 in the longitudinal direction of the tray. Each of the projections 11 has a chamfered tip 12 to facilitate its insertion through the aperture 8.

In order to fix a strip of lead flashing 13, as shown in Fig. 3, to the front edge of the base portion 1 of the tray, one edge of the flashing is provided with a series of perforations at the same spacing as, and of much the same diameter as the apertures 8. The flashing has its perforated edge placed below the portion 7 and abutting the upstanding step above the hinge 10 with its perforations in register with the apertures 8. The flange 9 is then bent upwards about its hinge 10 so that the projections 11 pass through the perforations in the flashing and through the apertures 8 after which, in order to anchor the flashing positively in position, the tips 12 of the projections 11 may be heated so that buttons are formed on their ends to prevent them from pulling out of the apertures 8.Alternatively increased heat may weld the tips of the projections 11 to the upper face of the portion 7.

The flange 9 is thus held in its upwardly bent position so that the edge of the flashing remains sandwiched between the flange 9 and the portion 7.

When the flashing strip 13 has been fixed to it, the cavity tray is set in a horizontal mortar joint 14 of the outer skin 15 of a cavity wall. The gully 5 lies in the cavity 16 of the wall and the rear wall 2 extends upwardly and rearwardly across the cavity 16 with the portion 3 in contact with the outer face of the inner skin 17 of the wall. Owing to the resilience of the polypropylene of which the tray is moulded, the portion 3 can be held pressed tightly against the face of the inner skin of the wall to form a substantially watertight joint.

The damp proof strip shown in Fig. 4 of the drawings comprises a base portion 1' corresponding to the base portion 1 of the cavity tray with a stepped portion 7' and a-flange 9' connected by a hinge 10' together with holes 8' and projections 11' for fitting a flashing strip to its front edge in exactly the same way as with the cavity tray described with references to Figs. 1 to 3.

Although it is usual practice to insert the edge of a flashing strip underneath a damp proof strip or tray, the portions 7 and 7' may be downwardly stepped from the portion 1 or 1' and then the flange 9 or 9' may initially extend upwardly and subsequently be bent downwards into position. In this case the edge of the flashing is then placed over the portion 7 or 7', but this still forms a satisfactory fixing of the flashing strip because the flange 9 or 9' still overlies the flashing strip and forms a watertight joint between the flashing strip and the portion 1 of the tray or damp proof strip.

In the illustrated examples, the flanges 9 and 9' are continuous along the length of the base portion or of the damp proof strip. They may alternatively be formed discontinuously in sections. If this is done, it is desirable for the flange 9 or 9' to project downwards so that there is a continuous watertight part of the flange or damp proof strip above the flashing at the junction between the edge of the flashing and the tray or damp proof strip.

Claims

1. A damp proof strip or cavity tray for building into a brickwork or blockwork cavity wall to form a damp proof course which extends through the outer skin and across the cavity of the wall, the strip or tray being injection moulded from resilient thermo-plastics plastics material and comprising a base portion for building into a horizontal joint of the outer skin of the wall, a cavity portion projecting from the rear edge of the base portion for bridging the cavity and an integerally formed clip portion for fixing a strip of flashing to the front edge of the base portion, the clip portion comprising a flange extending along and projecting upwards or downwards from near the front edge of the base portion to which it is connected by an integral hinge of the plastics material, and projections and corresponding apertures along the flange and along the front edge of the ba'se portion, either the projections being on the flange and the apertures in the base portion or vice versa, the arrangement being such that when a strip of flashing having perforations at the same spacing as the projections and apertures is placed along the front edge of the base portion and the flange is folded about its hinge towards the base portion, the edge of the flashing is sandwiched between the flange and the front edge part of the base portion with the projections extending through the perforations and through the apertures to fix the flashing to the damp proof strip or cavity tray.

2. A damp proof strip or cavity tray according to Claim 1, in which the flange projects downwardly from the base portion, the projections are provided on the flange and the apertures are in the base portion.

3. A damp proof strip or cavity tray according to Claim 1 or Claim 2, in which the projections have chamfered ends to facilitate their entry into the apertures.

4. A damp proof strip or cavity tray according to any one of the preceding Claims, in which the flange is continuous along the length of the base portion.

5. A damp proof strip or cavity tray according to any one of the preceding Claims, which is formed of polypropylene.

6. A cavity tray according to any one of the preceding Claims, in which a rear wall portion is provided extending upwards and rearwards from the rear edge of the base portion, the rear wall portion forming the cavity portion of the tray.

7. A cavity tray according to Claim 6, which has an end wall at one end of the base portion, the end wall being joined integrally to the base portion and to the rear wall portion.

8. A cavity tray according to Claim 6 or Claim 7, which is provided with a gully extending along the base portion adjacent the rear wall.

9. A cavity tray according to Claim 8, in which the end wall is provided with a recess to receive the end of the gully of a tray which, in use, overlaps it.

10. A cavity tray according to Claim 1, substantially as described with reference to Figs. 1 to 3 of the accompanying drawings.

11. A damp proof strip according to Claim 1, substantially as described with reference to Fig. 4 of the accompanying drawings.