GB2244507A

GB2244507A - Cavity wall tie adapted to allow testing of fixings

Info

Publication number: GB2244507A
Application number: GB9012330A
Authority: GB
Inventors: Brian Peter Briscombe
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-06-02
Filing date: 1990-06-02
Publication date: 1991-12-04
Anticipated expiration: 2010-06-02
Also published as: GB2244507B; GB9012330D0

Abstract

A cavity wall tie comprises first end and second end fixings 28, 29 for respectively fixing within bore holes in outer and inner walls 16, 15 of a cavity 17, and a rod or other elongate element 18 for interconnecting the two end fixings 28, 29 and which can be disconnected from at least one of the end fixings whilst leaving both end fixings 28, 29 fixed within the respective bore holes, enabling independent tests to be carried out on the strength of both fixings. <IMAGE>

Description

Cavity Wall ties This invention relates to a cavity wall tie and more particularly to a replacement cavity wall tie.

It is common for post-war houses to have inner and outer walls separated by a cavity to prevent damp transfer and to thermally insulate the exterior from the interior.

Cavity wall ties are used in the house construction to provide mutual support between the two walls.

Chemical substances used in brick and cement in addition to water cause existing ties to corrode and fail after about 50 years resulting in the cracking and bulging of the exterior walls, which may possibly have to be demolished and rebuilt.

Methods of replacing cavity wall ties have been devised that cause little or no interference to the house occupiers. This commonly involves boring a network of small diameter holes through the exterior wall and into the interior wall. A replacement cavity wall tie is inserted into each bore hole and anchored to both walls either by adhesive bonding or by using a tie which can be radially expanded inside the bore holes.

Cavity wall tie replacement is a problem predominantly apparent in local authority housing, and is usually carried out by a sub-contractor under close supervision by a surveyor. It is a requirement that each wall tie is tested by the surveyor to determine whether the tie is anchored securely to both inner and outer walls. However, due to the nature of known ties it is impossible to test both independently, so the test has to be carried out on both simultaneously and may therefore give incorrect results.

We have now devised a cavity wall tie that enables independent tests to be carried out on the strength of In accordance with this invention there is provided a cavity wall tie comprising first and second end fixings for respectively fixing within bore holes in outer and inner walls of a cavity, and a rod or other elongate element for interconnecting the two end fixings and which can be disconnected from at least one of the end fixings whilst leaving both end fixings fixed within the respective bore holes.

In one embodiment, preferably the rod interconnects the two end fixings by means of internal screw threads on the first and second end fixings and an external screw thread on the interconnecting rod. Preferably in this embodiment the rod is removed and a second rod is provided for inserting through the outer fixing to engage the inner fixing only, so that the inner fixing can be tested independently.

In a further embodiment the rod preferably engages the inner fixing by means of a screw thread, and constrains the outer fixing between a collar fastened to the rod on one side of the fixing and a nut screwed onto the rod from the other side of the fixing. Preferably the outer fixing is provided with means for engagement by a tool for testing that fixing independently.

In accordance with this invention, there is also provided a method of independently testing the inner and outer fixings of a cavity wall tie as defined above, the method comprising applying a force to either end fixing when both are fixed within their respectve bore holes, but the rod is disconnected from at least one of them.

In the first embodiment, preferably the interconnecting rod is removed and replaced with a second rod to engage the inner fixing only, and subsequently a force is applied to the second rod to measure the inner fixing strength.

The second rod may be withdrawn to engage the outer wall fixing so that a similar test may be carried out on that fixing.

Alternatively the interconnecting rod may be used to test the outer fixing instead, and also the outer fixing may be tested before the inner is tested.

In the second embodiment, preferably the interconnecting rod is screwed fully into the inner fixing, and a force is subsequently applied to the rod to test the strength of the inner fixing. To test the outer fixing strength an externally threaded tube is screwed into the outer fixing, to which a force may be applied.

Embodiments of this invention will now be described by way of example only and with reference to the accompanying drawings in which: FIGURE 1 is a cross section through a cavity wall whose walls are tied together by an embodiment of a cavity wall tie in accordance with this invention.

FIGURE 2 is a cross section of the device of Figure 1 having its inner fixing tested.

FIGURE 3 is a cross section of the device of Figure 1 having its outer fixing tested.

FIGURE 4 is a cross section through a cavity wall whose walls are tied together by another embodiment of a cavity wall tie in accordance with this invention.

FIGURE 5 is a cross section of the device of Figure 4 having its inner fixing tested; and FIGURE 6 is a cross section of the device of Figure 4 having its outer fixing tested.

Referring to Figure 1 of the drawings, there is shown a metal cavity wall tie fastened to an inner wall 15 and outer wall 16, and spanning a cavity 17 between the two walls 15, 16. The wall tie comprises a first end 29 and a second end 28 interconnected by a threaded rod 18. The first end 29 is located axially in a bore hole in the outer wall 16 and consists of an elongate internally threaded tube 21 located between two plastic collars 23, 22 having their axis in line with the axis of the threaded tube 21.

A cap 24 is provided that push-fits onto the plastic collar 23 from the external-side of the outer wall 16.

Annular rubber sealing rings 25, 26 are fitted to the periphery of the collars 23, 22 respectively and serve to contain a bonding material 13 that surrounds the threaded tube 21 located in the outer bore hole. Annular serrations (not shown) extend around the outer periphery of the threaded tube 21.

The second end 28 comprises an elongate rod 30 formed with radial tabs e.g. 31 at one end, and a coupling 12 at its other end. The end having tabs 31 is disposed axially into the bore hole in the inner wall 15 of the cavity that is filled with a similar bonding material 13 to outer wall fixing 11. The coupling 12 formed at the opposite end of the elongate rod 30 comprises a tube internally threaded along its axis in line with the axes of the elongate rod 30, collars 22, 23 and threaded tube 21. A base portion 32 joins the elongate rod 30 to the coupling 12. An annular rib 27 extends around the outside of the coupling 12.

An elongate externally threaded rod 18 is coupled axially to the internally threaded tube 21 at one end and to the internally threaded coupling 12 at its other end. A screwdriver slot 19 is cut in one end.

In use a bore hole is drilled through the outer wall 16 and into the inner wall 15 and is of a diameter greater than that of the cavity wall tie. The assembled cavity wall tie is inserted into the bore hole and adjusted to the correct length by turning the threaded rod 18, and to the correct wall spacing by turning the internally threaded tube 21 in relation to the threaded rod 18. The wall tie can then be removed, and the bore hole in the inner wall 15 filled with bonding material 13. The wall tie is re-inserted through the outer bore hole and its end 28 with tabs 31 is pushed into the bonding material 13 in the inner bore hole.

The gap between the outer bore hole and the threaded tube 21 is filled by pumping in bonding material 13.

The plastic collars 22, 23 at opposite ends of the threaded tube 21 prevent the threaded rod 18 from becoming coated in the bonding material 13. The annular rubber rings 26, 25 around the collars 22, 23 contain the bonding material inside the outer bore hole and around the threaded tube 21. The annular serrations around the threaded tube 21 fill with bonding material and serve to hold the tube 21 securely within the outer bore hole.

Once the bonding material 13 has hardened the strength of the inner and outer fixings can be determined independently as shown in Figures 2 and 3 respectively. The threaded rod 18 is unscrewed from both inner 10 and outer 12 fixings, and an elongate thin rod 20 comprising an enlarged threaded end 40 is screwed through the outer threaded tube 21 and into the threaded coupling element 12 as shown in Figure 2.

The rod 20 has a diameter along its central portion of less than the internal diameter of the threaded tube 21 in order for it to move freely through the tube 21. Thus a force F may be applied to the rod 20 to determine whether the inner fixing 10 can withstand the required stress.

Figure 3 shows how the rod 20 may be unscrewed to engage the outer fixing 11 only, a similar test may be applied to determine the strength of this fixing.

If both fixings meet the requirements the threaded rod 18 can be reinserted to couple the inner and outer fixings 10, 11 securely to each other. A plastics cap 24 is provided to fit to the external plastic collar 23 and prevents the cement applied to the outside of the bore hole (not shown) from contacting the threaded rod 18 in case it has to be removed in future years to retest the fixings. To prevent the passage of moisture from the outer wall 16 to the inner wall 15 an annular drip ring 27 is fitted to the coupling 12 disposed between the walls.

Referring to Figure 4 of the drawings, there is shown another embodiment of cavity wall tie fastened to an inner wall 15 and outer wall 16, and spanning a cavity 17 between the two walls.

The inner end fixing 58 of the wall tie comprises an elongate rod 50 formed with a course external screw thread, and tapered at one end. Its other end comprises a coupling 12 of similar construction to the coupling as described in the first embodiment.

The outer fixing end 59 comprises an elongate tube 61 disposed axially in the outer bore hole. The wall of the tube 61 is thinner at its end 62, and is formed with an internal screw thread. A thin tubular sleeve 64 fitted with an annular rubber sealing ring 66 is slid over the exterior end 62 of the elongate tube 61.

Another thin tubular sleeve 72 is slid over the opposite end of the elongate tube 61, and has a similar rubber sealing ring 73 at one end. Its other end is slid over the coupling 12 of the inner fixing end 58 and is fitted with an annular drip ring 27.

An elongate threaded interconnecting rod 70 has a first end coupled to the coupling 12, and a second end disposed axially within the bore of the elongate tube 61. An annular collar 71 is formed on the elongate interconnecting rod 70 adjacent its first end, so that it lies between the coupling 12 and the elongate tube 61.

A nut 63 is screwed onto the second end of the interconnecting rod 70 from the outside of the exterior wall and through the thin tubular sleeve 64 until it abuts the exterior end 62 of the elongate tube 61. A plastics cap 65 is provided that push-fits onto the sleeve 64 from the outside.

In use a bore hole is drilled through the exterior wall 16. The interior wall 15 in this case is wooden, and requires a different type of fixing to that used in the first embodiment however, both embodiments may be fitted with either of the inner fixings.

The wall tie is adjusted to the length required by turning the interconnecting rod 70 so as to move it in relation to the coupling 12. The nut 63 can then be tightened to clamp the elongate tube 61 between the collar 71 and the nut 63.

Once the wall tie is rigid, it can be inserted into the bore hole and screwed until the inner fixing is securely fastened to the inner wall 15.

The gap between the bore hole and the elongate tube 61 of the outer fixing end 59 is filled by pumping in bonding material 13. The thin tubular sleeves 64, 72, at opposite ends of the elongate tube 61 prevent the threaded interconnecting rod 70 from becoming coated in bonding material 13. The annular rubber rings 66, 73 around the sleeves 64, 72 contain the bonding material inside the outer bore hole and around the elongate tube 61 which has external annular serrations (not shown) to aid the bond between itself and the bonding material 13.

Once the bonding material has hardened the strength of the inner and outer fixings can be determined as shown in Figure 5 and 6 respectively. The interconnecting rod 70 is screwed fully into the coupling 12 so that its collar 71 no longer abuts the outer fixing end 59, after the nut 63 has been removed. A force F may be applied to the interconnecting rod 70 to independently test whether the inner fixing 10 can withstand the required stress.

To test the outer fixing 11 a special tool 90 having a tubular end which is externally screw threaded is rotated until it engages the internal screw thread formed in the exterior end 62 of the elongate tube 61. A similar force may be applied to the tool 90 to determine the strength of this fixing.

Once both fixings 10, 11 have met the requirements the interconnecting rod is unscrewed until its collar 71 abuts the outer fixing end 59. The nut 63 can then be replaced and tightened to interlock inner and outer fixings securely. Before the bore hole is plugged with cement or other facing material from the outside a cap 65 is push-fitted on the outer fixing end 59 to protect the threads from the facing material.

Claims

1) A cavity wall tie comprising first and second end fixings for respectively fixing within bore holes in outer and inner walls of a cavity, and a rod or other elongate element for interconnecting the two end fixings and which can be disconnected from at least one of the end fixings whilst leaving both end fixings fixed within the respective bore holes.

2) A cavity wall tie as claimed in claim 1 in which the rod or other elongate element interconnects the two end fixings by means of internal screw threads on the first and second end fixings and an external screw thread on the interconnecting rod or other elongate element.

3) A cavity wall tie as claimed in claim 1 in which the rod or other elongate element is removable and a second rod is provided for inserting through the outer fixing to engage the inner fixing only, so that the inner fixing can be tested independently.

4) A cavity wall tie as claimed in claim 1 in which the rod or other elongate element engages the inner fixing by means of a screw thread, and constrains the outer fixing between a collar fastened to the rod on one side of the fixing and a nut screwed onto the rod from the other side of the fixing.

5) A cavity wall tie as claimed in claim 4 in which the outer fixing is provided with means for engagement by a tool for testing that fixing independently.

6) A cavity wall tie substantially as herein described with reference to Figures 1 to 3, or with reference to Figures 4 to 6, of the accompanying drawings.

7) A method of independently testing the inner and outer fixings of the cavity wall tie of any preceding claim, the method comprising applying a force to either end fixing when both are fixed within their respective bore holes, but the rod or other elongate element is disconnected from at least one of them.

8) A method as claimed in claim 7 for testing the cavity wall tie of claims 2 and 3 in which the interconnecting rod is removed and replaced with a second rod to engage the inner fixing only, and a force is applied to the second rod to measure the inner fixing strength.

9) A method as claimed in claim 6 for testing the cavity wall tie of claims 2 and 3 in which the interconnecting rod is removed and replaced with a second rod to engage the outer fixing only, and a force is applied to the second rod to measure the outer fixing strength.

10) A method as claimed in claim 7 for testing the cavity wall tie of claims 4 and 5 in which the interconnecting rod or other element is screwed fully into the inner fixing, and a force is applied to the rod to test the inner fixing strength.

11) A method as claimed in claim 7 for testing the cavity wall tie of claims 4 and 5 in which an externally threaded tube is screwed into the outer fixing and a force is applied to the tube to test the outer fixing strength.

12) A method of independently testing the inner and outer fixings of a cavity wall, the method being substantially as herein described with reference to Figures 1 to 3, or with reference to Figures 4 to 6, of the accompanying drawings.