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Wall tie corrosion, Yorkshire’s wall tie time bomb

5 February 2012

Trouble is afoot in Yorkshire’s housing.

Wall tie corrosion became our business in 1985 are we are twenty six years older than they we were then the house I was checking with rusty wall ties were only fifty years old when wall tie corrosion was first noticed, so they’ve aged by another 50%. Bear in mind too, that in the first 25 years of life there was no corrosion ┬áthe ties were still protected by a healthy zinc coating or paint. In effect they are twice as old now, as they were when corrosion first began in earnest. Rust breeds rust, like when you notice it on an old car wheel arch; Not there one day and bursting out all over the place on the next. Houses are no different…….

Cavity wall tie failure in Leeds, York and Harrogate

In the past few years we’ve seen many more bulging walls and partial re-builds than in the previous twenty odd years combined.

Gable walls are most at risk and we recently had to deal with one, which was past saving, in Leeds. Other very severe and precarious ones have been seen in Wakefield, Sheffield, Harrogate, Huddersfield and York too. It’s only a matter of time before someone gets hurt, when an outside leaf is sucked over in strong winds.

Old houses; pre-war, usually have thick section ties, which cause cracking when they rust. Look for horizontal cracks in bed joints or render. However, post war houses may have thin section wire ties installed. millions of poor quality wire ties were imported in the 60s & 70s. These rarely open cracks and can fail without the slightest warning.

Only a boroscope or chisel can check for these, but care is needed. Any wall tie survey must be thorough; a tie is only as strong as its weakest section; which may not be the bit which is visible in the cavity, via boroscope.

The other problem, which is growing, is cavity wall insulation in houses which are suffering from wall tie corrosion. Once the insulation is in place, corrosion continues, opening up the bed-joints as the ties rust and split the beds. Water gets into the insulated cavity. The insulation is ruined and performs poorly. Installing cavity wall ties in a house which already has insulation present is full of pitfalls. Remedial ties can bridge the cavity, compressing and contaminating the insulation. This leads to damp penetration and condensation, caused by ‘cold bridging’ and direct penetrating damp.

Wall tie replacement is a specialist job at the best of times. However, if a building has cavity wall insulation in place, extreme care is essential. Diligent specialists who have identified the problem and catered for it in their remedial specification should be employed. I see too many ‘specialist wall tie survey reports’ where the presence of existing insulation hasn’t even been mentioned, let alone covered in the priced specification.

Our wall tie survey service covers all the major towns in Yorkshire, Lincolnshire and Derbyshire. So Leeds, Sheffield, Bradford, Harrogate and York are all within reach – if you need wall tie advice or a survey call us.

Image Gallery - Boroscope view of a corroded wall tie

Boroscope image of a rusty wall tie