On Sat, 19 Jun 2004 23:58:30 +0100, Andy Hall wrote:
On Sat, 19 Jun 2004 22:24:16 GMT, Phil Addison
wrote:
The builder had replaced the original sash windows with uPVC, and the
sills are now concrete, and I suspect the sill heights have been
increased. These sills are not 'bought' concrete ones but appear to have
been cast locally, possibly in-situ. The finish is pretty poor and the
top surface seems to be hand trowelled and not very flat. In fact there
are some hollows that retain little puddles on the sill with the worst
damp problem. I gave both sills a thorough soaking with silicone fluid a
couple of weeks ago and this soaked into them very readily, so I am
wondering if they are porous (or were, before siliconing).
It rather sounds like there is the problem right there, Phil.
I had exactly the same situation in the first house that we bought,
except it was the ground floor windows. The walls had been rendered
following an injection damp treatment.
I also did the soaking in silicone fluid thing. It did have some
effect but water would still find its way past.
In the end, the cills were taken out and replaced with proper ones and
the problem stopped.
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 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.
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.
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.
Phil
Phil
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