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What is a Wall Tie?
External walls are normally constructed of 2, 4" walls built 3" apart. To stop these walls collapsing a wall tie is placed across the cavity to tie both leafs together. A wall tie is normally made of metal which is coated with zinc or bitumen. (example No1 in right hand picture).
What is wall Tie Failure?
Wall tie failure is the corrosion of the protective coating of the wall tie, (example No 2 in right hand picture) and not as most people assume the actual breaking of the tie. (example No 3 in right hand picture)
Why replace the wall ties?
The metal wall ties rust over a period of time, this rusting will cause the tie to expand up to 7 times the original thickness, assuming a tie is approximately 4mm when new it could expand up to 28mm.
The pressure caused by the ties expanding causes horizontal cracking, as seen in the picture (left) above, bulging of the damaged walls and in extreme cases the collapse of damaged walls.
When Should Wall Ties Be Replaced.
Wall Ties should be replaced between stages 2 and 3 of the above picture, this will ensure that the rusted tie cannot cause structural problems and involve the property owner with the expense of rebuilding.
The property in the picture above had to have sections of walling rebuilt as structural damage had occurred.
How are wall ties treated
1. New ties are installed by drilling through the outer leaf 65mm into the inner leaf of wall.
2. A new tie similar to the example on the right of the page is installed. These ties work by expanding to grip the outer and inner sections.
3. The existing ties are then located using an electronic wall tie locator, metal detector.
4. The mortar around the tie in the outer wall is then removed and the tie is then isolated, isolation can take on many forms.
5. Like coloured mortars are used to fill in holes made for installation and isolation.
Isolation of the existing ties is very important, if the ties are not treated further
damage will occur at a later date.
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