Q. We recently had our wall-ties replaced and whole house repointed. Although we have never previously had a problem with damp, we now have substantial penetrating damp down one external wall. We had to have separate contractors in to do both jobs and each contractor is now saying that it is the 'others' responsibility to remedy the problem.

Broadly speaking we have been happy with the repointing work carried out, and are wondering if there is any chance the damp has been caused by the replacement work on the wall ties. Have you ever come across this situation and if so, what was the cause?

Submitted by: UB 

A. We have never heard of the situation you describe in relation to the sequence of events. Cavity walls are there to prevent moisture penetration being a problem. The only passage by which moisture may traverse the cavity is via the wall ties that connect the inner and outer leaf of brickwork. The new ties installed should have been fitted angled slightly towards the outside and they should also have a 'drip' in the middle to force any moisture to drip off before it reaches the inner leaf.

The only other possibility is that your walls have cavity insulation present? Some of these do transmit moisture despite claims to the contrary. How is the penetration showing itself? Is it circular patches over the entire wall at regular centres which would be characteristic of moisture via wall ties. Is it upstairs and downstairs? Or is it uniform and is any mould growth present? Has the wall in question ever received an application of silicone water repellent?

May be able to offer more advice with answers to the above questions
 
 REPLY
Thanks for the prompt reply Peter. To be honest we're absolutely stumped. Neither myself nor my husband are in the building trade, and we are having considerable difficulty pinning down our contractors into accepting the blame.
 
First and foremost - this is a new problem. We bought house 2.5 years ago and knew that the pointing needed doing although as I say we'd never had problems with damp. In re-financing the house in order to get the pointing done this summer, the surveyor recommended the wall-ties needed to be done at the same time. There is cavity wall insulation - however, this was done before we moved in and the company who did the wall-ties reckons they have never had a problem with this before.
 
It's in circular patches down the wall (personally having been up there to look, I think it more or less matches up to the wall ties, but haven't measured this exactly), and there is some damp which does not directly relate to the wall tie (a small patch but could be due wicking? Just guessing here).
 
No, there has never been any water repellent on the surface as far as we know. Our pointing contractor has recommended one called permaguard microshield and offered to carry out the work pending the formal investigations by the wall-tie guys.
 
The position we're dreading, however, (because it's more or less already started) is one contractor blaming the other and not taking responsibility. The wall-tie contractor has already picked up on two very small patches where the pointing is not water tight and blaming this for the wide spread damp patches. As I say - personally I think this is tenuous as it seems to match up with the wall ties.
 
Anyway the answers to the remainder of your questions are below.
 
Just to let you know we're based in Cardiff and were wondering if we need to call in independent advice, whether or not your company covered this area or could recommend an alternative. Thanks in advance.
 
 1) Is it circular patches over the entire wall at regular centres which would be characteristic of moisture via wall ties?
 
Yes - reasonably regular patches, but don't have access to the whole wall to see if it is more wide spread.
 
 2) Is it upstairs and downstairs?
 
Down the stair well external wall. Yes upstairs and downstairs
 
 3) Or is it uniform and is any mould growth present?
 
Not sure what you meant by uniform but no, it's definitely patches of damp, but there is now mould growth, but it didn't start like this. The mould has developed in the last 5 days.
 
4) Has the wall in question ever received an application of silicone water repellent?
No but it has been suggested.
 
REPLY
Sounds very much like the wall ties are transmitting moisture across the cavity especially if it is in regular patches that correspond to the new wall tie positions. If the wall tie contractor does not co-operate and you want to take this further you would need an independent expert opinion (not another contractor) but seek the advice of a solicitor or Citizens Advice Bureau first. One final thought is that it is just possible that the exterior face of the wall had been treated with a silicone previously and the new pointing has now disturbed this. Even so the new ties should be installed in such a way to make moisture transmission impossible. Good luck.