For some time wall tie corrosion has tended to be pigeon-holed as a defect of pre-war housing. It’s common in 1930s semis and its true; my wall tie specialist company’s bread and butter is pre-war dwellings.
However, over the past ten years I’ve noticed a steady drift in our work, which these days includes more and more post war commercial properties.
The critical period is just post war to the mid 80s when very many sites were plagued with cheaply imported galvanised wire ties. These had a pathetically thin galvanic layer and soon start to rust, especially in exposed and hi-rise situations.
The problem has grown quietly because the obvious ‘tram-line’ cracking associated with corrosion of older thick section (fishtail) ties is usually absent. Unless an invasive inspection, via boroscope of removal of bricks is done, the situation is ignored.
Now that lenders are back in super cautious mode, surveyors are inclined to dig a bit deeper, hence we are getting more calls to help out; in the surveying, specification and contracting.
Whilst there is not always horizontal expansion cracking to look out for, there are often other signs, such as stepped cracks and uneven brickwork, where large panels have been sucked and pushed out of alignment by wind loadings, with the ties often corroded or sparsely installed (another growing problem).
Wall tie corrosion is a potential issue in any cavity wall house or commercial dwelling, built prior to 1985. Inspection is easy and cheap in most cases so there really is little point in taking the risk and assuming all is well.
Recent wall tie corrosion projects have included an 11 storey apartment block in Huddersfield, where the ties were corroding and were ‘shot-fired’ into the concrete columns, which is a real no-no as far as long term fixing reliability is concerned. A five storey office block in Leeds was found to have very badly corroding wire butterfly wall ties, as was a further six storey office block in Huddersfield.
Certainly, if purchasing a cavity wall house or commercial building pre-war or even pre 1985, a thorough wall tie survey should be carried out.
Brick-Tie survey commercial buildings and domestic housing, for wall tie corrosion, all over Yorkshire – call 0800 591 541 for details.
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