EP0183362A2

EP0183362A2 - Wall tie

Info

Publication number: EP0183362A2
Application number: EP85307209A
Authority: EP
Inventors: Michael Douglas Hoyland; Graham Edward Haycox
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; GB8430162D0; EP0183362A3; GB2167782A; IE57020B1; IE852546L; GB8524917D0

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 upirght 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.

Description

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 masonry 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 compression.
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 encourage penetration of moisture into the inner leaf.

Conventionally, wall ties have provided a drip formation centrally in the cavity. In some forms, the metal is bent or deformed downwardly which can cause the compressive strength of the tie to be reduced. Alternatively, it has been suggested to provide cut outs in the metal of a wall tie which have downwardly projecting lips. However this alternative can give rise to weakness of the tie in tension.
Furthermore, many forms of wall tie currently in use can be misused by a bricklayer putting them in an inverted position or reversed end for end from the correct theoretical position in the cavity wall. When incorrectly positioned, moisture may be caused to go into the inner leaf or rapid mortar build up may be encouraged for example.
It is an object of the present invention to provide a new or improved wall tie which enables some or all of these disadvantages to be overcome or reduced.
According to the invention there is provided a wall tie comprising a rigid elongate strip-like member including a pair of end portions 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.
The arched formations may be of generally U-shape, V-shape or truncated or polygonal.
Preferably, both. end portions are substantially coplanar.
The tie may be symmetrical about its mid 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 way of example only with reference to the accompanying drawings in which;

FIGURE 1 is a plan view of a first embodiment of wall tie,
FIGURE 2 is a side elevational view of the tie shown in Figure 1,
FIGURE 3 is an end elevational view of the tie shown in Figures 1 and 2,
FIGURE 4 shows scrap side elevational views of three modified forms of cavity bridging portion for a wall tie,

Referring firstly to the wall tie shown in Figures 1 to 3 of the drawings, it comprises a metal strip of steel, which is preferably stainless 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 Figure 1 it presents only a very thin edge in an upward direction so that any mortar falling from a higher level onto the wall tie is discour- ged 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 Figure 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 part of an inverted generally vee shaped arched profile as seen in the side elevational view of Figure 2. The edge 19.of the tie then turns upwardly to form an upright arched profile 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 its 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 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 Figure 2 of the drawings, 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 Figure 2 but is reversed end for end. Similarly, if the tie is simply reversed 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 Figure 4 of the drawings, the scrap elevational views show modified forms of cavity bridging part which can be used in substitution for that of Figure 2..
Figure 4a shows a truncated rather than vee shaped arched profile, with an arch 20a, a main downwardly projecting moisture drip formation 18a and a subsidiary moisture drip formation 21a indicated on the drawings. Again, the tie is symmetrical about a dotted line 23a.
Figure 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, Figure 4c shows a profile very similar to that of Figure 2 but with rounded, rather than angled arched profiles.
The chevron type mortar key illustrated provides 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 particularly 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 context of this specification.

Claims

1. A wall tie 10 comprising a rigid elongate strip like member including a pair of end portions 11, 12 adapted to be secured respectively to the inner and outer leaves of a cavity wall; and a cavity bridging portion 13 joining the end portions 11, 12; characterised in that the cavity bridging portion 13 of the tie has a pair of twists 17, 22 adjacent respective end portions 11, 12, whereby the major part of the cavity bridging portion 13 lies in a generally upright plane in use, the overall profile of the cavity bridging portion 13 including an upwardly arched formation 20 and an inverted arched formation 18.

2. A wall tie according to Claim 1 further characterised in that the tie is symmetrical about its mid point 23.

3. A wall tie according to Claim 2 further characterised in that the tie has a mirror image symmetry about its mid point 23.

4. A wall tie according to Claim 2 further characterised in that the tie has inverted symmetry about its mid point 23.

5. A wall tie according to any preceding claim further characterised in that the inverted arched profile 18 lies immediately adjacent the upright arched profile 20.

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

7. A wall tie according to any preceding claim further characterised in that both end portions 11, 12 are substantially coplanar.

8. A wall tie according to any preceding claim further characterised in that one or both end portions 11, 12 of the tie are provided with a mortar key in the form of projections 15, depressions or cut-outs.