GB2133820A - Tie for a cavity wall - Google Patents

Abstract

The tie (1) includes first and second annuli (2,3) rigidly connected by a shaft (4). The first annulus can be pivotably secured to one leaf of the cavity wall structure, and the second annulus can be pivotably secured to another leaf of the cavity wall structure. <IMAGE>

Description

SPECIFICATION Tie for a cavity wall structure This invention relates to a tie for a cavity wall structure.

A typical cavity wall structure consists of two leaves of wall, and the two leaves are usually independent of one another. Commonly, one of the leaves corresponds to an internal wall of a building structure, and the other corresponds to an external wall.

Although both of the walls are often brick walls, this is not essential. For example, in houses having a timber frame construction, one of the walls may be a brickwork skin, while the other can be a timber frame.

It is known to incorporate ties between the two leaves of the cavity wall structure in order to provide the structure with additional rigidity and strength . These ties are extremely important since they often provide the only connection between the leaves of a cavity wall structure.

Prior ties have often been made of zinc coated metal, and these are subject to severe corrosion attacks, particularly at the internal face of the external leaf. This occurs due to water penetrating the mortar in which the ties are embedded, and also because of condensation between the leaves.

Special metals and alloys are available to prevent such corrosion, but these are expensive. Even such specially constructed ties are susceptible to a problem common to all metallic items, that is, they are very effective conductors of heat and sound.

The leaves of most cavity wall structures are prone to horizontal movement. Vertical movement can also occur, but this is usually relatively small compared with the horizontal movement.

Furthermore, the movement of each leaf is usually independent of the other leaves because of the different environmental conditions which each experiences. Such movement can cause the tie to become loose within the mortar, and this substantially reduces their effectiveness. The ties can also become loose during the construction of the cavity wall structure, since they can easily be knocked out of place.

According to the invention there is provided a tie for a cavity wall structure comprising a first part adapted to be pivotally secured to a first leaf of the cavity wall structure, and a second part adapted to be pivotally secured to a second leaf of the cavity wall structure, said first and second parts being rigidly connected.

Advantageously the first part comprises an annulus having a pivotal axis which passes perpendicularly through the centre of the annulus.

In one embodiment the second part also comprises an annulus having a pivotal axis which passes perpendicularly through the centre of the annulus.

In an alternative embodiment the second part comprises a member having an aperture for receiving a screw to facilitate fixing of the member to a timber frame.

Preferably the first and second parts are connected by a shaft, and desirably additional strengthening is provided on the shaft adjacent its connection with the first and second parts.

It is also preferable that protrusions are provided around the shaft in order to prevent water freely passing along the shaft. It is preferred that the tie is made from a plastics material but it may be made from a corrosion resistant metal or other material if desired.

It is desirable that a recess is provided on both faces of the or each annulus between the inner and outer edges of the or each annulus.

Reference is now made to the accompanying drawings in which: Figure 1 is a perspective view of one embodiment of a tie according to the invention; Figure 2 is a plan view of the tie shown in Figure 1; Figure 3 is a side elevation of the tie shown in Figures 1 and 2; Figure 4 is a cross section of a leaf of a cavity wall structure incorporating a tie according to the invention; Figure 5 is a plan view of a second embodiment of cavity wall tie according to the invention; and Figure 6 is a side elevation of the tie shown in Figure 5.

Referring to Figures 1 to 3 a tie for a cavity wall structure is generally designated 1. The tie consists of a first part, provided in the form of an annulus 2, and a second part, provided in the form of an annulus 3, the annulus 2 and 3 being connected by a shaft 4. Recesses 2a and 3a are provided in the annuli 2 and 3 respectively.

Recesses 2a are provided on both faces of the annulus 2 between an inner edge 2b and an outer edge 2c. Similarly, recesses 3a are provided on both faces of the annulus 3 between an inner edge 3b and an outer edge 3c.

A side web 5 is provided attached to the shaft 4 and annulus 2 in order to provide additional strengthening at the joint between the shaft and the annulus 2. Side web 6 fulfills a similar function between the shaft 4 and the annulus 3.

The shaft 4 is provided with circumferential protrusions 7 which serve to prevent water passing along the shaft.

Annuli 2 and 3 may, in use, pivot about axes A and B respectively, which pass through the centre of each annulus. The inner edge 2b of the annulus 2 defines a cylindrical space, and the inner edge 3b of the annulus 3 defines a cylindrical space.

Figure 4 shows how the tie 1 is embedded in a leaf of a brick wall. Bricks 20 and 21 are separated by mortar 22 in a leaf generally designated 23. A plug of mortar 24 forms within the cylindrical space, and abuts against surface 2dof the inner edge 2a, thereby impeding the movement of the tie 1 through the mortar. However, the plug 24 does not prevent the tie 1 from pivotting about the axis A. The tie 1 can pivot about the axis A without under going any lateral movement, and hence does not tend to work itself loose from the mortar.

It is preferred that there is no bond between the mortar and the material of the tie, so that the pivotal movement of the tie is not restricted.

The relative ease with which the tie may pivot helps to reduce the shearing forces at the junctions between the annuli 2 and 3 and the shaft 4. Consequently the principal forces within the tie are tensile or compressive.

Referring to Figures 5 and 6 a tie 30 is shown.

The tie 30 is the same as the tie 1 shown in Figures 1 to 4, with the exception that the second part comprises a member 31.

The tie shown in Figures 5 and 6 can be used, for example, in buildings having a timber frame construction to provide strength between a brickwork skin and a timber frame. The annulus 2 is attached to the mortar of the brickwork skin, and the member 31 is attached to the timber frame.

The member 31 can be attached to a wall of the timber frame by means of a screw (not shown) which passes through an aperture 32 of the member 31.

The member 31 is provided with an arcuate surface 31 a, to permit pivotal movement of the member 31 with respect to the wall to which it is connected. The tie 31 can thus pivot about axis C, which is parallel to axis A, and about axis D which is transverse to axis A.

The resistance of the timber frame to which the tie 31 is attached provides sufficient flexibility to permit this pivotal movement.

When the tie is made from a plastics material the heat and sound conduction is reduced, and this helps to prevent the formation of cold spots on internal walls, and to lessen noise transmission through the cavity wall structure. The plastics ties are also easier to handle and much safer for the construction personnel than metallic ties.

In addition the cross-sectional shape of the annulus increases the surface area of the tie in contact with the mortar.

Claims (9)

1. A tie for a cavity wall structure comprising a first part adapted to be pivotally secured to a first leaf of the cavity wall structure, and a second part adapted to be pivotally secured to a second leaf of the cavity wall structure, said first and second parts being rigidly connected.

2. A tie according to Claim 1 in which the first part comprises an annulus having a pivotal axis which passes substantially perpendicularly through the centre of the annulus.

3. A tie according to Claim 1 or 2 in which the second part comprises an annulus having a pivotal axis which passes substantially perpendicularly through the centre of the annulus.

4. A tie according to Claim 1 or 2 in which the second part comprises a member having an aperture for receiving a screw to facilitate fixing of the member to a timber frame.

5. A tie according to any preceding claim in which the first and second parts are connected by a shaft.

6. A tie according to Claim 5 in which additional strengthening is provided on the shaft adjacent its connection with the first and second parts.

7. A tie according to Claim 5 for 6 in which protrusions are provided on the shaft in order to prevent water passing along the shaft.

8. A tie according to any one of Claims 2 to 7 in which a recess is provided on both faces of the or each annulus between the inner and outer edges of the or each annulus.

9. A tie according to any preceding claim which is made from a plastics material.

1 0. A tie for a cavity wall structure substantially as herein described with reference to and as shown in the accompanying drawings.