On Sun, 20 Jun 2004 14:40:53 GMT, Phil Addison
wrote:
Thanks Andy, that's encouraging to know I'm on the right track.
On ours there was render instead of the special plaster normally
recommended after a damp treatment. I ripped it all off.
I haven't heard of that 'special plaster'. Is it water resistant in case
the damp treatment didn't work, or just tolerant to being applied to
still-wet brickwork?
I've been trying to find what the reason for the special plaster
(although I don't think it's very special) is. THe standard
procedure with injected dampcourses has been to rip off plaster to a
height of about 1 metre, treat and then replaster with this stuff.
It may have something to do with preventing migration of salts, but I
can't remember now - I don't think it was to stop damp though. Even
then I don't think that this would apply to an upstairs situation.
I thought these were the reasons for rendering, though I really can't
see why one should render if the source damp is eliminated.
The bricks being damp isn't that surprising. They could also be
porous. If the dampness is in a patch below the cill then the
implication is of water soaking down rather than through the bricks.
I wasn't surprised that they got damp, just that they were STILL wet
after the long dry spell we have had, interspersed with some baking sun
on the wall. I'm presuming it is the render both sides that trapped the
water and prevented it drying out over this period.
Sounds like it, so it seems to me that the important thing is to
identify and fix and test that the damp through the bricks really is
eliminated and then replaster. Trapping water in the brick seems
like a bad idea to me.
What I need now is advice on is what to do to make good the inside wall.
I am not convinced that re-rendering it is a good idea - I want to stop
the damp at source, and the original render put on to contain it has not
worked very well. Is a 'waterproof' rendering really waterproof?
Certainly trapping any water behind any making good is asking for
trouble.
Yes, I aim to cure it at source. The problem is being sure of what the
source is.
I suspect that under the pressure of a couple of feet of water inside the
brickwork wet will seep through; or could it be that the builder didn't
mix the render correctly?
I am also worried about the poor quality of the sills, and suppose that
we may have to replace them if wet continues to enter the wall in spite
of the silicone treatment. In one sense, not rendering the inside will
at least allow me to quickly see if wet is still entering from outside,
whereas I imagine rendering it will delay the occurrence of future damp
but not totally stop it.
I remember testing mine with a hose played on it for about half an
hour. Even after the siliconing (which did help a bit), water
continued to seep through.
You mean it penetrated from the sill to the inside in 1/2hr? I am
looking for a test method to prove it is the sill, as opposed to say
leakage around the window frame, which I have recently re-sealed with a
decent bead. I thought that it would take many hours or a few days to
penetrate through.
It was in a few minutes, it was so bad. In this particular
situation, the house faced a park and the wind would drive the rain at
the front of the house. Once it started raining and the wind was
blowing a bit, even in quite light rain the wall would become wet.
What is involved in replacing a sill should that be needed?
To be honest, I didn't do it, a builder who was doing other work did.
Basically though, it wasn't that difficult. He removed the window
frame and then carefully chopped out the mortar from around the cill
and removed and replaced it with a "new" one - actually a stone one
from a reclamation place. No further trouble after that.
These sills seem to butt up against the frame edge rather than go under
the frame, and in one of the pair the sill is very high, nearly up to
the uPVC drain outlet (about 1/4" clearance). I wonder if this could be
a cement render on top of the actual sill - as per Andrew's post. I'll
need to investigate that possibility next.
Could be - i.e. a poor repair to an old cill.
Phil
Phil
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