Print this pageCAVITY WALL TIES
According to BRE research out of nine million dwellings constructed with cavity walls, two million suffer wall tie corrosion or failure and are in need of specialist remedial wall tie replacement. Often the problem is found to be exacerbated by insufficient ties having been installed during construction.
- Inadequate protection - prior to the 1930s ties were not galvanised.
- Substandard galvanising - the British Standard for weight of galvanising was actually reduced between 1964 and 1981.
- Chemical action - for instance where corrosive black ash mortar has been used.
- Location - such as marine environments with driving rain and salt laden atmospheres.
Symptoms
- Horizontal cracking at regular intervals in external mortar joints.
- Outward bulging of the wall.
- The lifting of roof edges.
- Internal cracks.
Solution
The first step in a repair programme is a survey to determine the extent of the problem.
The position of existing wall ties is plotted using a metal detector and then an endoscope is used to examine their condition. Bricks may have to be removed for the physical examination of sample ties.
Installation of Replacement Ties
A range of alternative wall tie designs is available - resin, mechanical or cementitious -depending on the type and condition of the masonry involved. In most cases the existing ties are isolated to prevent further corrosion.
Arrange a Cavity Wall Survey
I'm sure that businesses come and go in your trade but your Company has been in existence for a long time. My recent experience demonstrates why this is the case.
Our 30 year guarantee had almost expired when we recently discovered woodworm infestation in the previously treated roofing joists. I understood why you wanted to charge the refundable fee for the survey and took the risk in requesting it. However, I anticipated that you would attempt to "wriggle" out of the guarantee and was ready for an argument with your surveyor. My cynicism was totally unfounded. Your surveyor efficiently identified the problem and confirmed that the area would be re-treated - I didn't have to say anything. Your operative subsequently did the treatment work efficiently and with a high standard of housekeeping. In both cases, they were friendly and courteous.
