Hi all,
I have recently moved into a newly aquired property, built in the 60's. The brickwork seems to be a bit crumbly in places which I think could be symptoms of frost damage(?) I believe this can be prevented by painting some sort of silicone sealant onto the outside walls.Anyone know of such a probuct and/or where to get it?
Thanks in advance.
Colin
Frost damage is caused usually by moisture in the bricks freezing and thus expanding and exfoliating the outer layers. Silicone treatments are supposed to prevent the water penetrating, so the theory is feasible. However, where is the damage? If it is below the damp proof course, then the likelyhood is that the wrong sort of bricks were used.
AWEM
Thanks for the reply. They are fairly low down so it is possible. If this is the case what is the course of action?
Colin.
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One often sees a vertical cement render plinth fitted to cover the damage. On one of my houses it had such a plinth comprising a sandwich of slate with cement either side. I would be concerned about bridging the damp proof course.
Below dpc less porous bricks should be used.
AWEM
It seems to be the same bricks above and below the dpc. Would it be possible to add some sealant to the bricks below the dpc as a preventative measure?
I'm not convinced that would work cos lots of the damp in the below dpc bricks will be migrating from the ground rather than falling directly onto the face of the brick. A French drain would keep the bricks drier and also helps to stop water splashing onto the wall
Anna
I would be wary about adding impermeable coatings like this until you are sure of the source of the moisture - you may in fact make matters worse. What type of wall is it, solid or cavity? It could be a simple as someone having repointed with an inappropriate mortar in the past.
Its a cavity wall. So yes Im not sure for definate what this is a symptom of, could be damp or frost. Is there an obvious way of telling? (apart from the obvious of feeling the bricks to see if they are damp).
Colin.
a waterproof coating would prevent evaporation, thus worsening things considerably.
A French drain gives more brick surface area exposed to air, thus more evaporation, thus lower water content. But for all I know it might be just a case of lowering ground levels a bit. Ground should be at least
6" below floor level. Or removing rubbish etc that keeps sun and wind off the brickwork.NT
Hi,
Thanks for the response. The offending brickwork in question is along the side of the house next to a tarmac drive, so I think putting in a French drain might be tricky. Its only seems to be a few random bricks around the wall not an entire area which I why I thought it may not be simply damp, although they are all towards the bottom of the wall.
Colin.
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Chop them out and replace them if it is only a few. It may simply be variation in the bricks firing when made
AWEM
That had occured to me. As I understand it you can't mix and match different brick types due to expansion etc, is that correct? If thats the case is there an easy way to determine the type of bricks used in a wall?
Thanks again.
Colin.
Your property may be too new for this to be a consideration, but the other one to watch for is where the bricks are soft and the place was built with a lime mortar. The mortar is softer than the brick and accommodates a small amount of movement for expansion etc. Also much of the evaporation will occur from the more permeable mortar rather than the brick. This all works fine until someone repoints a bit of it with a hard cement based mortar which is harder than the brick. Any evaporation now has to occur from the brick surface (meaning it stays wetter for longer and is more susceptible to frost damage), you will sometimes get more white salt deposits on the bricks, and any movement or expansion is not tolerated. Nett result is one good frost and the front of the brick spalls off.
I'd lay bets that you are getting splashing on the wall as rain bounces back from the tarmac pavemnet. That would account for only occasional bricks being affected and mostly low down
You can solve this problem by laying astroturf on the path
Anna
Thats certainly possbible although the offending wall is under a carport and semi sheltered. Its more possible at the moment since the recent high winds have reomoved half of it....
A rethink then ... Has the carport been there since the 60s too? Could it be old damage?
Anna
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