Penetrating damp problems can cause severe problems to buildings, whether it’s a traditional solid red brick, stone, or even modern cavity wall construction. Penetrating damp is normally quite simple to diagnose as the problem is normally visual, and can be quite localised to the problem area in most cases.
Good diagnosis is key to fixing the problem, and also to make sure no unnecessary works are carried out.
I thought I would share a case study of a property that we recently surveyed and had to carry out remedial works to stop the severe wind driven rain penetrating through the external cavity wall into the internal cavity skin and causing damp patches to the internal walls and ceilings.
The property is a 1970’s house, my survey instruction was to find out exactly where the damp was coming in at first floor level, and price for repairs as necessary.
My tools for this penetrating damp survey were the Flir E60 BX thermal imaging camera and a Flir MR77, these are my preferred tools for this type of survey.
Because of the long term penetrating damp problem, I knew it was likely that there could be a problem with the wall ties, so a boroscope inspection would also be needed to examine the inner cavity to see the condition of the wall ties.
Thermal imaging also highlights problem areas, so using this method points me to what are most probably the worst areas (wet) that have been suffering from the penetrating damp the longest, this helps me in selecting a wall tie suffering from corrosion.
Cavity wall ties installed up to 1981 didn’t have enough zinc coating that is why there is still considerable wall tie corrosion in 1970’s houses.
The picture below shows the extent of the wall tie corrosion, some bricks were also removed as these were badly damaged on the edges from when the property was first constructed.
On grinding out the bed joints prior to re-pointing it was also evident along the whole gable elevation that all the wall ties were badly corroded.
The below pictures show the poor workmanship of the original construction, bricks were layed the wrong way down, and the bed joints were all over the place with differing depths and perps were also differing in width.
We initially ground out the mortar bed with our dust free chasing equipment and re-pointed the wall with a sand and cement mix. The wall was protected with hessian whilst drying down to prevent rapid drying during the curing process.
Remedial stainless steel wall ties were installed to BRE Digest 401 and most importantly we tested the stainless steel wall ties with our Hydrajaws calibrated pull out testing equipment.
Once the pointing had fully cured the walls were washed down and allowed to dry again, this was to ensure our breathable “Deep Shield” uv resistant external waterproofing coat was as pure and clean as possible to ensure it was going to be breathable.
The building has since had its first test recently and stayed completely dry, and I was told the rain was bouncing off the wall, a happy customer.
If you are interested in wall ties Brick-Tie Limited in Yorkshire have a really good and informative web site. Of course they don’t work in my area (thank God), but if you need wall tie or structural repair advice in the North Of England they’re the best by far.