GB2167782A

GB2167782A - Wall tie

Info

Publication number: GB2167782A
Application number: GB08524917A
Authority: GB
Inventors: Graham Edward Haycox; Michael Douglas Hoyland
Original assignee: PRESS BAT HOLDINGS Ltd
Current assignee: PRESS BAT HOLDINGS Ltd
Priority date: 1984-11-29
Filing date: 1985-10-09
Publication date: 1986-06-04
Also published as: GB2167782B; EP0183362A2; IE57020B1; GB8524917D0; EP0183362A3; GB8430162D0; IE852546L

Abstract

A wall tie (10) of strip metal has a pair of twists (17), (22) adjacent its end portions (11) and (12) which are formed with mortar keying formations (15). The central cavity bridging portion (13) lies upright and has an overall profile which includes an arched formation (20) and an inverted arched formation (18) affording a water drip. The tie (10) is symmetrical with direct or reversed symmetry about its mid point (23) so that it can be used inverted or reversed end to end without losing its effectiveness in preventing moisture penetration. <IMAGE>

Description

1 GB2167782A 1

SPECIFICATION

Wall tie This invention relates to wall ties for cavity walls.

It has principally been devised for use in wall ties for joining brick to brick or brick to block in a conventional masonary cavity wall.

The main requirements of a wall tie for use in any cavity wall are; 1. To connect the inner and outer leaves of the wall together against both tensile forces pulling them apart and compressive forces tending to push them together. Metal ties are usually preferred as having greater strength than plastics, particularly in compres sion.

2. To prevent any moisture which may condense in the cavity from flowing into the inner leaf of the cavity wall.

3. To avoid providing any ledge on which mortar from higher levels can settle if it falls into the cavity, bridging the cavity to encour age penetration of moisture into the inner leaf. 90 Conventionally, wall ties have provided a drip formation centrally in the cavity. In some form, the metal is bent or deformed down wardly which can cause the compressive strength of the tie to be reduced. Alterna tively, it has been suggested to provide cut outs in the metal of a wall tie which have downwardly projecting lips. However this al ternative can give rise to weakness of the tie in tension.

Furthermore, many forms of wall tie cur rently in use can be misused by a bricklayer putting them in an inverted position or re versed end for end from the correct theoreti cal position in the cavity wall. When incor rectly, positioned, moisture -may be caused to go into the inner leaf or rapid mortar build up may be encourage for example.

It is an object of the present invention to provide a new or improved wall tie which en- 110 ables some or all of these disadvantages to be overcome or reduced.

According to the present invention there is provided a wall tie comprising a rigid elon gated strip-like member including a pair of end 115 portions adapted to be secured respectively of the inner and outer leaves of a cavity wall; and a cavity bridging portion joining the end portions; the cavity bridging portion of the tie having a pair of twists adjacent respective end 120 portions, whereby the major part of the cavity bridging portion lies in a generally upright plane in use, the overall profile of the cavity bridging portion including an upwardly arched formation and an inverted arched formation.

The arched formations may be of generally U-shalied, V-shaped or truncated or polygonal.

Preferably, both end portions are substan tially coplanar.

The tie may be symmetrical about its mid 130 point and the symmetry may be mirror-image or inverted.

The inverted arched profile may lie immediately adjacent the upright arched profile.

A further arched profile or inverted arched profile may be provided in addition to said upright arched profile and said inverted arched profile.

One or both end portions of the tie may be provided with a mortar key in the form of projections, depressions or cut outs.

Several embodiments of the invention will now be described by of example only with reference to the accompanying drawings in which:

Figure 1 is a plan view of a first embodi ment of wall tie, Figure 2 is a side elevational view of the tie shown in Fig. 1, Figure 3 is an end elevational view of the tie shown in Figs. 1 and 2, Figure 4 shows scrap side elevational views of three modified forms of cavity bridging por tion for a wall tie, Referring firstly to the wall tie shown in Figs. 1 to 3 of the drawings, it comprises a metal strip of steel, which is preferably stain less steel but which may be galvanised mild steel. The first and second end portions of the tie are indicated at 11 and 12 and the tie is generally indicated at 10. A central cavity bridging portion of the tie is generally indicated at 13.

In the example shown, the end portions 11 and 12 are substantially the same, being formed with a series of chevron shaped projections and depressions 15 to act as a mortar key when the end portions are embedded in the mortar of the outer and inner leaves of a cavity wall respectively. The extreme free end portions of the tie may be rounded at 16 to reduce the risk of injury to a bricklayer which might be caused by sharp corners.

In use, the end portions 11 and 12 lie in the same generally horizontally plane in the inner and outer leaves of the cavity wall. However, the cavity bridging portion 13 lies in an upright vertical plane in use. Thus, as seen in plan view in Fig. 1 it presents only a very thin edge in an upwardly direction so that any mortar falling from a higher level onto the wall tie is discourged from settling and tends to drop off the wall tie without forming a mortar bridge between the inner and outer leaves of the wall.

Similarly, any moisture condensing on the tie tends to run down this thin vertically upright cavity bridging portion.

Referring now to Fig. 2 of the drawings, it will be seen that at the twist 17 where the end portion 11 leads into the cavity bridging portion 13, one edge of the tie dips downwardly below the level of the end portion 11. This -edge continues downwardly to a moisture drip formation 18 forming the lowermost 2 GB2167782A 2 part of an inverted generally vee shaped arched profile as seen in the side elevational view of Fig. 2. The edge 19 of the tie then turnsupwardly to form an upright arched pro- file generally indicated at 20, before again turning somewhat downwardly to a further moisture drip formation 21, where it merges with a reversed twist 22 and hence with the other end portion 12 of the wall tie.

It will therefore be seen that moisture is encouraged to drip off the tie at at least two positions on it lower edge 19, namely the first moisture drip formation 18 and the second such formation 21. Any moisture adjacent the inner or outer leaf of the cavity wall falls onto 80 the twisted portions 17 or 22 and tends to run towards the downwardly inclined side edge 19 of the tie, and hence down to either of the drip formations 18 or 21.

However, considering Fig. 2 of the draw- 85 ings, it will be seen that the profile of the cavity bridging portion of the tie is generally symmetrical about the dotted line 23 with a reversed symmetry.

If the wall tie is inadvertently put into the cavity upside down, then the profile is very similar to that shown in Fig. 2 but is reversed end for end. Similarly, if the tie is simply re versed end for end from the position shown, the profile is similar. In each case, there is a pair of moisture drip formations separated by an upwardly inclined arch wholly above the level of the upper of the moisture drip formations. The tie therefore continues to function even if placed in the cavity reversed end for end or upside down.

It will be seen that there are no cut outs in the material of the tie which encourage tensile failure. Furthermore, there are no corrugations or bends in the material of the tie in the cavity bridging part which could give rise to a collapse of the tie under compression.

Referring now to Fig. 4 of the drawings, the scrap elevational views show modified forms of cavity bridging part which can be used in 110 substitution for that of Fig. 2.

Fig. 4a shows a truncated rather than vee shaped arched profile, with an arch 20a, a main downwardly projecting moisture drip for- mation 18a and a subsidary moisture drip formation 21a indicated on the drawings. Again, the tie is symmetrical about a dotted line 23a.

Fig. 4b shows a profile in which the underneath edge 19b of the tie has a pair of arches 20b separated by a main moisture drip formation 18b, the cavity bridging portion also including two subsidiary moisture drip formations 21b. The cavity bridging portion is symmetrical about the line 23b but this is not an inverted symmetry. Each side of the line 23b is a mirror image of the other.

Finally, Fig. 4c shows a profile very similar to that of Fig. 2 but with rounded, rather than angled arched profiles.

The chevron type mortar key illustrated pro- vides secure fixing against both tension and compression forces when it has been embedded in the mortar of the inner and outer leaf brickwork. This form of mortar key has been found to reduce the risk of vertical and or horizontal cracking of the masonry which may occur when wall ties having other types of mortar key are subjected to strong tension or compression forces, since these forces can be resolved into vertical forces in the masonry.

The tie is slender in width compared to other metal strip-like ties. This results in a relative saving in the metal used which may result in substantial cost savings particularly where the tie is to be made of stainless steel. Additionally, however, the tie has sufficient flexibility to be capable of accommodating some small discrepancy in height between the coursing levels of the inner and outer leaves of masonry. In each of the examples illustrated, such minor discrepancies do not have any substantial effect on the mortar or moisture shedding properties of the tie. It is parti- culafly noteworthy that none of the forms of the tie relies solely on a single moisture drip formation which could be pushed out of position by some misalignment in the inner and outer coursing levels.

The arched formation need not necessarily be arched at both of its edges. Thus, for example, a formation having a flat lower edge and a part circular arched upper edge is to be considered as an arched formation in the con- text of this specification.

Claims

1. A wall tie comprising a rigid elongated strip-like member including a pair of end por- tions adapted to be secured respectively to the inner and outer leaves of a cavity wall; and a cavity bridging portion joining the end portions; the cavity bridging portion of the tie having a pair of twists adjacent respective end portions, whereby the major part of the cavity bridging portion lies in a generally upright plane in use, the overall profile of the cavity bridging portion including an upwardly arched formation and an inverted arched formation.

2. A wall tie according to Claim 1 wherein the arched formations are of generally Ushape.

3. A wall tie according to Claim 2 wherein the arched formations are of generally V- shape.

4. A wall tie according to Claim 3 wherein the arched formations are of generally polygonal shape.

5. A wall tie according to any preceding claim wherein both end portions are substantially coplanar.

6. A wall tie according to any preceding claim wherein the tie is symmetrical about its mid point.

7. A wall tie according to Claim 6 wherein 3 GB2167782A 3 the tie has a mirror-image symmetry about its mid point.

8. A wall tie according to Claim 7 wherein the tie has inverted symmetry about its mid point.

9. A wall tie according to any preceding claim wherein the inverted arched profile lies immediately adjacent the upright arched profile.

10. A wall tie according to any preceding claim wherein a further arched profile, or inverted arched profile is provided in addition to said upright arched profile and said inverted arched profile.

11. A wall tie according to any preceding claim wherein one or both end portions of the tie are provided with a mortar key in the form of projections, depressions or cut outs.

12. A wall tie substantially as hereinbefore described with reference to and as illustrated in Figs. 1 to 3 of the accompanying drawings.

13. A wall tie substantially as hereinbefore described with reference to and as illustrated in Figs. 1 to 3 of the accompanying drawings as modified by Fig. 4a.

14. A wall tie substantially as hereinbefore described with reference to and as illustrated in Figs. 1 to 3 of the accompanying drawings as modified by Fig. 4b.

15. A wall tie substantially as hereinbefore described with reference to and as illustrated in Figs. 1 to 3 of the accompanying drawings as modified by Fig. 4c.

Printed in the United Kingdom for Her Majesty's Stationery Office, Dd 8818935, 1986, 4235. Published at The Patent Office, 25 Southampton Buildings, London, WC2A 'I AY, from which copies may be obtained.