GB2223556A - Stabilising cavity walls by wall ties - Google Patents

Abstract

To restabilise a cavity wall structure (1, 2, 3) a wall tie comprising two parts 12, 13 having mating inclined surfaces is inserted into a hole bored into the two leaves 1, 2 of the wall, the part 12 wedging against the part 13. The hole is bored in an upwardly inclined direction commencing at a mortar course (4) and extending through the wall (1) and approximately three quarters of the way into the second wall (2). After boring this hole an expandable plastic sheath member (5) which may be longitudinally split is inserted into the hole (a) and the sheath member (5) may include a conically tapered end (6). Thereafter the rigid rod (7) formed from the two parts (12, 13) with longitudinal mating inclined surfaces is driven into the sheath member (5). <IMAGE>

Description

TITLE Stabilisation of Cavity Walls This invention relates to the stabilisation of cavity walls and is more particularly concerned with restabilising cavity walls wherein the existing cavity wall tie members have or are suspected to have deteriorated to an unacceptable extent. As is known, during building cavity walls are constructed with metal tie members between the two walls with the tie members being embedded in respective courses of mortar. The tie members generally comprise either galvanised twisted wall ties or galvanised wire of a butterfly profile.

Such wire members deteriorate relatively rapidly and may thus fail to provide the necessary stability. This invention seeks to provide a method for restabilising a cavity wall by introducing an effective tie member means between the two walls in situ.

According to this invention there is provided a method for the restabilisation of cavity walls which method comprises boring a hole through the outer cavity wall and partially into the inner cavity wall, and thereafter locating a rigid rod member in the aperture to form a tie between the two walls of the cavity, wherein the rigid rod member is formed from parts which have longitudinally extending mating inclined surfaces to form a wedge ramp.

This invention also provides a wall tie member for the restabilisation of cavity walls comprising an outer sheath member for locating within a bore provided in brickwork and a rigid inner rod member adapted to be driven into the sheath to force same outwardly to grip the brickwork wherein the rigid rod is formed by two or more parts having inclined mating surfaces extending longitudinally and arranged so that on insertion into a hole in brickwork, driving in one of said parts relatively to the other will cause outward expansion through co-operation of the inclined surfaces.

The rigid rod parts may be formed of metal or plastic or a combination thereof, for example one part of metal and another of plastic.

In a preferred construction two parts constitute the rigid rod member. In this arrangement one part of the rod may be inserted to be followed by the second part which is driven home with the mating inclined ramp surfaces providing outward expansion to firmly grip the brickwork.

Preferably the hole is bored in an upwardly angled direction and optionally also angled laterally. In the former case, ingress of water into the aperture is prevented and in the latter case a more effective key between the two cavity walls is provided by a dovetailing effect between adjacent ties.

After the rod has been introduced the aperture may be closed off by plugging with mortar and, to provide an improved visual effect, the aperture is preferably bored by starting into a mortar course in the outer cavity wall. The rod may comprise galvanised steel with a roughened or helically profiled surface which when driven into the brickwork or the sheath will provide an adequate locking key.

In a further embodiment a plastic sheath member is inserted into the bored hole and the rigid rod member or part thereof of metal or other material driven into the sheath member to thereby cause same to expand outwardly providing a firm grip into the brickwork. In this arrangement the plastic sheath may have profiled outer surfaces to augment the gripping action.

The end of the sheath may include an annular collar which abuts the face of the outer brick thereby to prevent the sheath being driven inwardly during the action of driving home the rod member parts. After inserting the rod members into holes bored into the mortar course the brickwork can be re-pointed to conceal the repair.

The method is further enhanced by laterally offsetting the angle of the bore hole in alternate directions with respect to adjacent ties to provide the dovetail locking action. A longitudinally extending groove in the rod parts may be provided to assist in the expulsion of air from the blind cavity which is formed in the inner course of brickwork.

Embodiments according to the invention are shown by way of examples in the accompanying drawings wherein: Figure la shows a cavity wall structure in part section with two embodiments of tie members, Figure ib shows a detail of a sheath end, Figure 2 shows a wall section similar to Figure la with further embodiments of tie members, and Figure 3 shows in detail a tie member.

Referring to Figure 1 of the drawings, a cavity wall comprises an outer course of brickwork 1 and an inner course of brickwork 2 separated by a cavity 3. To restabilise such a cavity wall structure a hole is bored in an upwardly inclined direction commencing preferably, but not essentially, at a mortar course 4 and extending through the wall 1 and approximately three quarters of the way into the second wall 2. After boring this hole a plastic sheath member 5 which preferably will be longitudinally split is inserted into the hole (a) and the sheath member 5 will preferably include a conically tapered end 6 which engages the opening to the hole.

If the plastic sheath is capable of expanding readily then the longitudinal split may not be necessary.

Thereafter a rigid rod 7 formed from two parts 12, 13 with longitudinal mating inclined surfaces is driven into the sheath member 5 and the arrangement is such that the sheath member is caused to expand outwardly by the rod parts along the line of the longitudinal division and thereby provide a gripping action to firmly stabilise the two brick courses. After insertion the bored aperture 4 may be plugged with mortar in a repointing operation.

Yet another arrangement (b) is shown using a sheath 10 similar to that previously described but including an annular collar 11 which abuts the outer face of the brickwork 1. Here again a steel rod 7 formed from parts 12, 13 is driven into the sheath 10 and, after insertion, the collar 11 can be cut or broken off.

The sheaths 5 and 10 may include a conical end plug 15 to facilitate driving into the brickwork (see Figure 1b) and a longitudinal split 16.

Figure 2 shows an embodiment wherein the rod is formed from two parts 12 and 13 with mating inclined faces forming a ramp. With this construction one part of this rigid rod is first located within the bored hole (a) and the second part thereafter inserted and driven home whereby an outward expanding force is generated through the inclined mating surfaces. The surplus rod part protruding can be cut off flush with the outer face as required. This arrangement has the advantage of enabling the rod to be easily inserted and positioned and thereafter firmly tightened into the hole by the wedging action. This arrangement also provides for an even expanding action to occur over the total length of the bearing area formed within the brickwork. This embodiment can be used with a plastic sheath as in Figure 1 and as shown at (b).

Referring to Figure 3 the expansion produced by the wedges 12,13 can be controlled by cutting off the end 12a of one wedge 12 to provide a sufficient linear movement for outward expansion. The surplus end 12b projecting from the brickwork can then be removed.

To facilitate driving in the sheath and/or the rigid rod lubricating means may be provided and all the embodiments may include some form of longitudinally extending groove along the peripheral surface or between the mating surfaces to enable air to be exhausted as the rod or parts are driven home.

Claims (12)

1. A method for the restabilisation of cavity walls which method comprises boring a hole through the outer cavity wall and partially into the inner cavity wall, and thereafter locating a rigid rod member in the aperture to form a tie between the two walls of the cavity, wherein the rigid rod member is formed from parts which have longitudinally extending mating inclined surfaces to form a wedge ramp.

2. A method according to Claim 1, wherein two parts form the rigid rod member, one part being inserted into the hole followed by the second part which is driven home with the mating inclined ramp surfaces providing outward expansion to firmly grip the brickwork.

3. A method according to Claim 1 or 2, wherein the hole is bored in an upwardly angled direction and/or laterally angled direction.

4. A method according to any preceding claim, wherein after the rod has been introduced the hole is plugged.

5. A method according to any preceding claim, wherein a plastic sheath member is inserted into the bored hole and the rigid rod member or part thereof of metal or other material driven into the sheath member to thereby cause same to expand outwardly providing a firm grip into the brickwork.

6. A wall tie member for the restabilisation of cavity walls comprising an outer sheath member for locating within a bore provided in brickwork and a rigid inner rod member adapted to be driven into the sheath to force same outwardly to grip the brickwork wherein the rigid rod is formed by two or more parts having inclined mating surfaces extending longitudinally and arranged so that on insertion into a hole in brickwork, driving in one of said parts relatively to the other will cause outward expansion through co-operation of the inclined surfaces.

7. A method or tie member according to any preceding claim, wherein the rigid rod parts may be formed of metal or of plastic or a combination thereof.

8. A method or tie member according to any preceding claim, wherein the rod comprises galvanised steel with a roughened or helically profiled surface which when driven into the brickwork or the sheath will provide an adequate locking key.

9. A method or tie member according to any preceding claim, wherein the end of the sheath includes an annular collar which abuts the face of the outer brick thereby to prevent the sheath being driven inwardly during the action of driving home the rod member parts.

10. A method or tie member according to any preceding claim wherein a longitudinally extending groove is provided in the rod parts to assist in the expulsion of air from the blind cavity which is formed in the inner course of brickwork.

11. A method for the restabilisation of cavity walls as described herein and exemplified.

12. A cavity wall tie member as described herein and exemplified with reference to the drawings.