Cavity Wall Tie Corrosion is the term used when the cavity wall ties between the inner and outer leaf in a traditional brick-built property corrode due to the breakdown of the original coating and the expansion of the metal alloy. Wall tie corrosion can seriously damage internal and external walls and can make a building unstable if the adhesion fully deteriorates.

Construction Design
The most commonly identified issues of wall tie corrosion occur in cast-iron fishtail ties, whilst the more recent tie is the butterfly-wire design. As cavity wall ties are likely to be exposed to moisture levels they are coated in galvanisation to resist corrosion. Over time, the galvanising can deteriorate and cause expansion in the installed tie. The photographs below show typical symptoms of wall tie failure .

Symptoms of Wall Tie Failure
The most common visible evidence is:
Horizontal Cracks – in the mortar at all levels but more prevalent at high level caused by expansion of wall ties and reduction in overall weight at height.
Bowed brickwork – caused by corroded, fractured wall ties or loss of adhesion. This may make a building unstable.

Identification
An experienced B.C.A (North-East) surveyor will carry out the following to establish the need for remedial work. 
• Carry out a professional inspection of your property, exposing wall ties either individually by a destructive survey or by use of a boroscope or via removal of brickwork to expose ties if deemed necessary
• Classify the level and seriousness of the damage.
• Compile a specification for all remedial works including access for safe working
• All options are agreed with clients before commencing
• Where necessary, local building control will be involved

B.C. Associates have been involved with the promotion and development of professional bodies relating to all remedial stabilisation work for decades and use validated suppliers from all across the UK. Please see our links for all of our partners nationwide and from across Europe and North America.

Standard Replacement
Our technicians will carry out works as noted typically:
• Design pattern for installation of wall ties in line with BRE guidelines
• Install stainless steel ties; design ties to be agreed to suit site needs
• Isolate or remove existing ties, thus removing the likelihood of further damage by expansion
• Make good disturbed work and leaving site clean and tidy

Cavity Wall Tie Corrosion and Masonry Stabilisation

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