My daughter's house has had a patch of damp appearing under the upstairs
windows since she bought the house 5 years ago from a builder (I did
warn her!!) who had done it up to re-sale. There was no sign of damp
then, it all being freshly decorated.

The property is an 1890 end terrace on a high exposed location facing
the prevailing wind, and rain does drive against this wall at times. The
outside is rendered with small chips (spar?) in a yellowish base. There
are a couple of hairline cracks in the render below the windows, and
that area has been treated a couple of times recently with silicone
fluid without any improvement to the damp patch.

There are two adjacent rooms with windows in identical situations, and
one has a large ugly damp patch below the sill, whilst the other shows
only a very small patch about 3" diameter.

The bad damp patch is about 3 ft wide by 1 ft high, starting 9" below
the sill. I did the 'glass-slip plasticined to the wall' test to verify
that it is damp and not condensation, and this was very clear with gross
condensation on the inside glass surface.

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).

The damp patch has slowly dried back since the winter, and left ugly
efflorescence marks behind. A test with my damp meter (a cheap squawk
type) confirmed the surface to be almost dry compared to the winter
wetness.

Having now siliconed the sills, as well as the walls, I am hoping that
further wet will be kept out, and so last week I decided to hack off the
plaster with a view to making good the interior efflorescence, but I
found some unexpected things.

The plaster turned out to be only a skim of 3-4 mms on a sand/cement
render. I assume that the builder did this to suppress the damp, but it
is obviously ineffectual, so I hacked it all off - that turned out to
quite a test for my cheapo Screwfix SDS+ drill, but was a dream compared
to doing it by hand. I found the render to be covering a real mess of
brickwork, but the main surprise was that the bricks were actually quite
wet, the wettest being right under the sill. I surmise now that the
problem IS that the sill is porous and water is percolating down from
the sill becoming trapped between the (hopefully) waterproof cement
render on the inside and outside surfaces. I suspect that the whole
inner wall is rendered, at least up to the sill level rather than just
over the damp area. Certainly the 4' x 1' area I hacked off did not
reach the limit of the render. Incidentally, i could not detect any
dampness on the outside rendered wall, perhaps not surprising as the
weather has been dry and warm.

I am leaving it for a few days to see how this wet dries out, now that
it can via the exposed inner brick surface.

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? 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.

What is involved in replacing a sill should that be needed?

Any advice or comments will be much appreciated.

Phil

The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
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Phil Addison
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On Sat, 19 Jun 2004 22:24:16 GMT, Phil Addison
wrote:

My daughter's house has had a patch of damp appearing under the upstairs
windows since she bought the house 5 years ago from a builder (I did
warn her!!) who had done it up to re-sale. There was no sign of damp
then, it all being freshly decorated.

The property is an 1890 end terrace on a high exposed location facing
the prevailing wind, and rain does drive against this wall at times. The
outside is rendered with small chips (spar?) in a yellowish base. There
are a couple of hairline cracks in the render below the windows, and
that area has been treated a couple of times recently with silicone
fluid without any improvement to the damp patch.

There are two adjacent rooms with windows in identical situations, and
one has a large ugly damp patch below the sill, whilst the other shows
only a very small patch about 3" diameter.

The bad damp patch is about 3 ft wide by 1 ft high, starting 9" below
the sill. I did the 'glass-slip plasticined to the wall' test to verify
that it is damp and not condensation, and this was very clear with gross
condensation on the inside glass surface.

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.




The damp patch has slowly dried back since the winter, and left ugly
efflorescence marks behind. A test with my damp meter (a cheap squawk
type) confirmed the surface to be almost dry compared to the winter
wetness.

Having now siliconed the sills, as well as the walls, I am hoping that
further wet will be kept out, and so last week I decided to hack off the
plaster with a view to making good the interior efflorescence, but I
found some unexpected things.

The plaster turned out to be only a skim of 3-4 mms on a sand/cement
render. I assume that the builder did this to suppress the damp, but it
is obviously ineffectual, so I hacked it all off - that turned out to
quite a test for my cheapo Screwfix SDS+ drill, but was a dream compared
to doing it by hand.

On ours there was render instead of the special plaster normally
recommended after a damp treatment. I ripped it all off.

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 found the render to be covering a real mess of
brickwork, but the main surprise was that the bricks were actually quite
wet, the wettest being right under the sill. I surmise now that the
problem IS that the sill is porous and water is percolating down from
the sill becoming trapped between the (hopefully) waterproof cement
render on the inside and outside surfaces. I suspect that the whole
inner wall is rendered, at least up to the sill level rather than just
over the damp area. Certainly the 4' x 1' area I hacked off did not
reach the limit of the render. Incidentally, i could not detect any
dampness on the outside rendered wall, perhaps not surprising as the
weather has been dry and warm.

I am leaving it for a few days to see how this wet dries out, now that
it can via the exposed inner brick surface.

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.

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.


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.




Any advice or comments will be much appreciated.

Phil

The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
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..andy

To email, substitute .nospam with .gl

In article ,
Phil Addison writes:
My daughter's house has had a patch of damp appearing under the upstairs
windows since she bought the house 5 years ago from a builder (I did
warn her!!) who had done it up to re-sale. There was no sign of damp
then, it all being freshly decorated.

That would probably be about the time to inspect and possibly
replace the sealant around the window.

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.

These actually sound like original rendered brick window sills.
I have these too, and thought they were concrete until one was
removed by a bricky.

The plaster turned out to be only a skim of 3-4 mms on a sand/cement
render. I assume that the builder did this to suppress the damp, but it
is obviously ineffectual, so I hacked it all off - that turned out to
quite a test for my cheapo Screwfix SDS+ drill, but was a dream compared
to doing it by hand. I found the render to be covering a real mess of
brickwork, but the main surprise was that the bricks were actually quite
wet, the wettest being right under the sill. I surmise now that the
problem IS that the sill is porous and water is percolating down from
the sill becoming trapped between the (hopefully) waterproof cement
render on the inside and outside surfaces.

My money would be on water leaking in around the window or from the
window's drainage.

I am leaving it for a few days to see how this wet dries out, now that
it can via the exposed inner brick surface.

It takes weeks for wet walls to dry out. IIRC, it took about
6 weeks for the single brick front wall of my fireplace to
dry out after I reopened the fireplace (blocked up with no
ventilation for probably 20 years).

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? 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?

--
Andrew Gabriel

Sounds like you have lousy sills which you should ideally replace
(particularly if they don't have a drip groove on the underside).
If you prefer to modify the existing, you need to get a flat surface,
preferably sloping away a fraction. Polyfilla Exterior filler is fairly easy
to use as a skim although I would use car body filler if you can face the
extra work. Then you need to get something genuinely waterproof on there.
Pliolite paint is good but any solvent based paint will be better than
conventional masonry paint, which is not at all waterproof IME.

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
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
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On 20 Jun 2004 01:05:33 GMT, (Andrew
Gabriel) wrote:

In article ,
Phil Addison writes:
My daughter's house has had a patch of damp appearing under the upstairs
windows since she bought the house 5 years ago from a builder (I did
warn her!!) who had done it up to re-sale. There was no sign of damp
then, it all being freshly decorated.

That would probably be about the time to inspect and possibly
replace the sealant around the window.

Certainly the frame seal was badly applied and next to useless, and I
re-did it a couple of weeks ago before applying the silicone to the
sill. I don't think that is the root cause though, largely because there
are two windows in identical situations both with equally poor seal and
only one has bad damp. The two sills are both poor but the one with the
bad damp also has hollows where water collects. At least the other
drains off, even though it may be porous to a degree.

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.

These actually sound like original rendered brick window sills.
I have these too, and thought they were concrete until one was
removed by a bricky.

That is most interesting, Andrew. I have not heard of that construction
before. Do you mean original brickwork sills, rendered at a later date?
I didn't think sand/cement render was available that early (1890's) or
am I wrong there? If it is rendered brick, I may be able to remove and
replace the render with proper waterproofer additive and hopefully make
a better finish of the slope.

I'm going to have a good look at that and perhaps drill to see if I can
hit brick. My daughter would be relieved not to have the upheaval of new
sills. On the other hand, the sills do look like cast ones - there is
evidence of framework marks on the front, and there is a cast drip
channel underneath.

My money would be on water leaking in around the window or from the
window's drainage.

That was certainly possible. I have now made a good seal all around the
frame, and it definitely was leaking along the bottom edge - caulk
broken away and evidence of wet under it. The drainage channels look OK,
but I suppose the uPVC frame itself might have a cracked bottom corner
joint allowing water to egress directly to the brickwork, though I
imagine that an unlikely failure. Also the inside of the openers is
quite clean, so it seems that little if any water is passing the rubber
seals to the frame innards.

Assuming the sills are in fact concrete, my big question now is how do I
prove that it is (or is not) the sill before embarking on replacing
them. I suppose once the internal bricks have dried out I could rig up
some kind of water drip to keep the sills soaked, but how long would I
have to run that to be sure it is not soaking through? This assumes that
the internals will actually dry out before the next storm!

I was toying with the idea of over-painting the sills to waterproof them
with, for example, one of Max Bone's products at
http://www.decoratingdirect.co.uk/Co...onry_Coatings/,
but I'm not sure if that would seal the sill completely or how durable
it is. If it will last 2-3 years before repainting it would probably be
preferable to sill replacement because my daughter is expecting a baby
in 11 weeks and is anxious to get the nursery decorated, for that is
what this room is to be. I would have to 'get a builder in' (aaargh!!
the shame of it) to do that and that will take a while to sort out.

I am leaving it for a few days to see how this wet dries out, now that
it can via the exposed inner brick surface.

It takes weeks for wet walls to dry out. IIRC, it took about
6 weeks for the single brick front wall of my fireplace to
dry out after I reopened the fireplace (blocked up with no
ventilation for probably 20 years).

Hopefully not that long as there is only about a height of 2ft of bricks
below the sill to dry out. Your fireplace presumably had wet brickwork
to a much greater height replenishing the opening as it evaporated from
there?

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? 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?

Given that I have exposed a 4' x 2' patch of brickwork, what is the
appropriate materials to make this good? I was planning on a background
of Carlite Browning with a skim of finish or multi-finish. Any hints
anyone?

Phil
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
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On Sun, 20 Jun 2004 13:23:57 +0100, "stuart noble"
wrote:

Sounds like you have lousy sills which you should ideally replace

Thanks for the input Stuart. Timescale is my problem for replacing them
- see my reply above.

(particularly if they don't have a drip groove on the underside).

They do have drip grooves.

If you prefer to modify the existing, you need to get a flat surface,
preferably sloping away a fraction.

The 'concrete' they are made of does seem to be fairly soft, and no
obvious concrete-type gravel visible at the surface. I did wonder if I
might be able to grind them down in-situ to get a decent run-off slope.
We had our limestone frontage restored last year and the stonemasons
used an air chisel to rough it back and a stone rasp to smooth it. I
wonder if I might achieve similar on these sills with my small SDS
chisel and/or an angle grinder if its not too hard. Don't know where to
get hold of a stone rasp though.

Polyfilla Exterior filler is fairly easy
to use as a skim although I would use car body filler if you can face the
extra work.

By 'extra work' do you mean sanding it smooth after it has gone off? I
had the impression that Polyfilla Exterior was not particularly durable
or perhaps I'm biased by the interior stuff.

Then you need to get something genuinely waterproof on there.

I'm not clear why you suggest both a skim and a waterproof paint.

Pliolite paint is good but any solvent based paint will be better than
conventional masonry paint, which is not at all waterproof IME.

That was my other question (see my reply above), so thanks - I will
avoid conventional masonry paint. I'm not familiar with Pliolite though
- what is it? By 'any solvent based paint' is that as in ordinary gloss
woodwork paint?

Phil
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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
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
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..andy

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"stuart noble" wrote in message ...
Sounds like you have lousy sills which you should ideally replace
(particularly if they don't have a drip groove on the underside).
If you prefer to modify the existing, you need to get a flat surface,
preferably sloping away a fraction. Polyfilla Exterior filler is fairly easy
to use as a skim although I would use car body filler if you can face the
extra work. Then you need to get something genuinely waterproof on there.
Pliolite paint is good but any solvent based paint will be better than
conventional masonry paint, which is not at all waterproof IME.

Just to offer an alternative based on my own experience.

I was suffering something similar with 3 windows built in an extension
and went through some of the steps mentioned. It was only in some
weather circumstances that there was leakage.

What I did notice is that the window cills didn't have a drip - they
were sealed with silicon or something to the concrete cill but the
actual drip part of the wooden cill appeared to have been removed when
the windows were installed; the only reason I can think of for this is
to make it easier for applying the external render. I re-created the
drip with an add-on to the wooden cill and the problem has never
reappeared after 10 years.

Rob

On Sun, 20 Jun 2004 18:10:09 +0100, Andy Hall wrote:

On Sun, 20 Jun 2004 14:40:53 GMT, Phil Addison
wrote:

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 found this http://www.travisperkins.co.uk/PDF/848737.pdf "Thistle
Dri-Coat: A cement-based undercoat plaster for application after
installation of a damp-proof course." Doesn't say why it should be used
though.

Also this helpful chart about which plaster to use on which surface
http://www.british-gypsum.com/immediacy-1331 indicates Thistle Browning
with suction control (my internal brickwork looks pretty soft/porous).

buildingpreservation explains, I think, what you are getting at
regarding "migration of salts" at
http://www.buildingpreservation.com/...ng%20facts.htm
I don't think salts are a significant problem in my case though, more
applicable to long term heavy dampness it seems.

I read somewhere that the background to use is Bonding, not Browning as
Bonding is lightweight with vermiculite bits in it, whereas Browning is
sand based, and now obsolete. Don't know how that squares with the
Thistle chart which does call it browning.

... I really can't see why one should render if the source damp
is eliminated.

Answering myself, the buildingpreservation paper explains this, and as I
say, I Don't think it necessary for my problem. Anyone diss/agree?

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.

I certainly don't plan to trap water!

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.

Surely that must have been a direct leak through a crack or something.
This damp took a long to appear and equally long to fade back when the
warmer weather came. My worry is what is the upper limit of time it
might take to get through rather less porous material. In other words
how long do I have to soak the outside and wait inside for signs before
I decide that is NOT the source? OK, I know there can be no definitive
answer to that one - finger in the wind territory!

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.

I'll be trying to determine if its just a render, or concrete
throughout, in the next couple of days.

Thanks again everyone for thought provoking inputs. I'll let you know
any developments.

By the way, should it come to sill replacement, is it essential to
remove the frame or is that just to improve access, i.e. allow access
from inside the room as well.

Phil
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On 20 Jun 2004 14:16:35 -0700, (Rob Graham)
wrote:

Just to offer an alternative based on my own experience.

I was suffering something similar with 3 windows built in an extension
and went through some of the steps mentioned. It was only in some
weather circumstances that there was leakage.

What I did notice is that the window cills didn't have a drip - they
were sealed with silicon or something to the concrete cill but the
actual drip part of the wooden cill appeared to have been removed when
the windows were installed; the only reason I can think of for this is
to make it easier for applying the external render. I re-created the
drip with an add-on to the wooden cill and the problem has never
reappeared after 10 years.

Thanks Rob, but mine do have drip channels already.

Phil
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Hi,

If you want a good sealer for the concrete sill have a look at
Bondaglass G4 eg:

http://www.arghamvillage.co.uk/products/details/180.html

Worth trying a sample area though to see what it looks like.

cheers,
Pete.

On Sun, 20 Jun 2004 23:47:07 +0100, Pete C
wrote:

If you want a good sealer for the concrete sill have a look at
Bondaglass G4 eg:

http://www.arghamvillage.co.uk/products/details/180.html

That's an interesting one - a pond sealer. Should be waterproof then!
Not sure about the colour though, Browny translucent, Mid Green, or
Black. Could over paint it I suppose. Thanks for the pointer.

Phil
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In article ,
Phil Addison writes:
On 20 Jun 2004 01:05:33 GMT, (Andrew
Gabriel) wrote:

These actually sound like original rendered brick window sills.
I have these too, and thought they were concrete until one was
removed by a bricky.

That is most interesting, Andrew. I have not heard of that construction
before. Do you mean original brickwork sills, rendered at a later date?

Rendered when built. All the houses in the terrace have the same
sills (1895). The render is very hard -- I was bashing away with
a scraper on it to get 100 years of paint off, and it doesn't
damage or even mark it. It is vulnerable if the render cracks
though -- water can get in and then freeze in the brickwork,
causing large chunks of the brickwork to fall off, which had
happened on one of mine.

I didn't think sand/cement render was available that early (1890's) or

Cement goes back to roman times. However, prior to Portland cement,
it was more expensive, so it wasn't used for everything like it is
today.

am I wrong there? If it is rendered brick, I may be able to remove and
replace the render with proper waterproofer additive and hopefully make
a better finish of the slope.

I think the only way the sill will be letting water in is if
there are cracks in the render.

I'm going to have a good look at that and perhaps drill to see if I can
hit brick. My daughter would be relieved not to have the upheaval of new
sills. On the other hand, the sills do look like cast ones - there is
evidence of framework marks on the front, and there is a cast drip
channel underneath.

Mine also has a drip channel. It's a bit far back for my liking
though.

I am leaving it for a few days to see how this wet dries out, now that
it can via the exposed inner brick surface.

It takes weeks for wet walls to dry out. IIRC, it took about
6 weeks for the single brick front wall of my fireplace to
dry out after I reopened the fireplace (blocked up with no
ventilation for probably 20 years).

Hopefully not that long as there is only about a height of 2ft of bricks
below the sill to dry out. Your fireplace presumably had wet brickwork
to a much greater height replenishing the opening as it evaporated from
there?

It was about a 2' square (plus much of the bricked up area which was
removed). It was quite waterlogged though.

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? 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?

Given that I have exposed a 4' x 2' patch of brickwork, what is the
appropriate materials to make this good? I was planning on a background
of Carlite Browning with a skim of finish or multi-finish. Any hints
anyone?

If you stop the water entry and let it all dry out, you can use
pretty much anything (personally, I use bonding coat as the scratch
coat). However, none of the gypsom-based plasters are suitable if
it's damp.

I have done a scratch (base) coat of cement (and lime if you like it)
and sand in a 1:1:6 ratio, with waterproofer added. Follow up 24 hours
later with regular plaster finish coat (no PVA required unless you
leave it much longer and the scratch coat has dried). The sand and
cement is very effective at keeping the water away from the plaster
finish coat. However, you'll probably need to let the wall dry out
first, at least so it doesn't feel and look wet.

--
Andrew Gabriel

By 'extra work' do you mean sanding it smooth after it has gone off?
That and polyester being generally sticky and difficult to work with.

had the impression that Polyfilla Exterior was not particularly durable
As a skim, more durable than any cement based mix

I'm not clear why you suggest both a skim and a waterproof paint.
Skim to get it smooth/flat and provide a better base for the paint.

I'm not familiar with Pliolite though- what is it?
A type of synthetic rubber I believe. Macphersons, Johnstones, and most of
the other trade outlets do it. Based on solvent naptha so not too
environmentally friendly.

By 'any solvent based paint' is that as in ordinary gloss
woodwork paint?
Yep, although a matt might look better on sills. Mine are coated in red
oxide primer which is quite a good match for adjacent brickwork.

Phil Addison wrote in message
If you want a good sealer for the concrete sill have a look at
Bondaglass G4 eg:

http://www.arghamvillage.co.uk/products/details/180.html

That's an interesting one - a pond sealer. Should be waterproof then!
Not sure about the colour though, Browny translucent, Mid Green, or
Black. Could over paint it I suppose. Thanks for the pointer.

I think a fibreglass resin would be better. G4 cures on contact with
moisture which may not be a good thing if the concrete is damp close to the
surface. Foul stuff to work with too.

On Sun, 20 Jun 2004 22:57:45 GMT, Phil Addison
wrote:

On Sun, 20 Jun 2004 23:47:07 +0100, Pete C
wrote:

If you want a good sealer for the concrete sill have a look at
Bondaglass G4 eg:

http://www.arghamvillage.co.uk/products/details/180.html

That's an interesting one - a pond sealer. Should be waterproof then!
Not sure about the colour though, Browny translucent, Mid Green, or
Black. Could over paint it I suppose. Thanks for the pointer.
Hi,

I think the tranlucent is more like a varnish colour. Another
possibility is a UV stabilised clear expoxy.

cheers,
Pete.

Phil Addison wrote in message . ..
My daughter's house has had a patch of damp appearing under the upstairs
windows since she bought the house 5 years ago from a builder (I did


big snip

I think you might be barking up the wrong tree here Phil.

It's almost certain that your problems are due to the outside
rendering and the poor detailing/workmanship of the window.

If you have a strong mix on the external wall (3:1) or in that region,
then it's virtually waterproof. (BRE say mix strength this will hold
back hydrostatic pressure). Any water that gets behind it has
nowhere to go to get out but through your internal walls.

You say that you have hairline cracks and also that the wall is on an
exposed elevation. Put these two together and add it to the poor
detailing of the cill – has he for instance just plonked it between
the reveals or is it inset. Is there a good seal to it, is there a
dpc beneath it, are you sure the drip mould works?

The question of the internal rendering is a red herring. It could be
plaster or render, as long as it isn't repeat isn't waterproof then
it's probably doing its job. If it were waterproof, the water would
slowly but surely go further and further down your wall until a big
rust red mushroom popped up between the floor joists.
Check the render, check the detail, keep the water out and you'll be
OK.
Easy when it's said like that in't it

Regards

Patrick

On 21 Jun 2004 09:05:57 -0700, (Meoww) wrote:

Phil Addison wrote in message . ..
My daughter's house has had a patch of damp appearing under the upstairs
windows since she bought the house 5 years ago from a builder (I did


big snip

I think you might be barking up the wrong tree here Phil.

It's almost certain that your problems are due to the outside
rendering and the poor detailing/workmanship of the window.

Must admit I tended to discount the external render because on the whole
face of the house there is damp coming through only under the sills of 3
windows (sorry, didn't mention the downstairs one before - that is only
a minor patch similar to the 2nd upstairs one). I imagine if the render
was duff it would come through in arbitrary places. But what you say is
quite possible, and I have rectified the useless seal between frame and
reveal and sill. The problem is finding out which of the possible entry
points is the cause.

Although there is a hairline vertical crack under the worst window, now
that I have exposed the brickwork inside it is clear that the wettest
course is the one right under the sill, getting progressively less wet
until it is dry at skirting level. That seems to point the finger at
either the sill itself or the sill/frame interface where I did find wet
behind the old sealant as I removed it.

If you have a strong mix on the external wall (3:1) or in that region,
then it's virtually waterproof. (BRE say mix strength this will hold
back hydrostatic pressure). Any water that gets behind it has
nowhere to go to get out but through your internal walls.

I understand that, but I have no idea what the external mix was. Is it
possible to test it somehow?

You say that you have hairline cracks and also that the wall is on an
exposed elevation. Put these two together and add it to the poor
detailing of the cill –

has he for instance just plonked it between
the reveals or is it inset.

I don't know quite what you mean. The frame is set about 3" in from the
inner wall surface with a narrow (about 3") inner wood sill. The
external reveal is about 6" deep.

Is there a good seal to it,

There is a good seal all round now.

is there a dpc beneath it,

Where should this dpc be? Directly under the sill I suppose. I don't
know if there is one. How can I find out? Good point though - if there
was a dpc it wouldn't matter if the sill was porous, right?

are you sure the drip mould works?

Well, I'm not SURE the drip channel works but it looks OK and is not
obstructed. I could run a hose over the sill to check.

The question of the internal rendering is a red herring. It could be
plaster or render, as long as it isn't repeat isn't waterproof then
it's probably doing its job. If it were waterproof, the water would
slowly but surely go further and further down your wall until a big
rust red mushroom popped up between the floor joists.

It was rendered internally, as I say, and clearly WAS trapping water. I
have hacked it off under the window now. It was pretty hard stuff, and I
guess waterproof (ish!) as it was dry on the surface and the bricks
behind were damp. Also the render I hacked off didn't appear obviously
damp - I'm pretty sure it was dry. I say "ish" because some damp did
penetrate and showed on the decoration.

Check the render, check the detail, keep the water out and you'll be
OK.
Easy when it's said like that in't it

Err, yes :-)

Thanks again for the ideas Patrick.

Phil
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On Mon, 21 Jun 2004 12:51:07 +0100, Pete C
wrote:

On Sun, 20 Jun 2004 22:57:45 GMT, Phil Addison
wrote:

On Sun, 20 Jun 2004 23:47:07 +0100, Pete C
wrote:

If you want a good sealer for the concrete sill have a look at
Bondaglass G4 eg:

http://www.arghamvillage.co.uk/products/details/180.html

That's an interesting one - a pond sealer. Should be waterproof then!
Not sure about the colour though, Browny translucent, Mid Green, or
Black. Could over paint it I suppose. Thanks for the pointer.
Hi,

I think the tranlucent is more like a varnish colour. Another
possibility is a UV stabilised clear expoxy.

Is that 'paint-on' or spread as a skim?

Phil
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Phil Addison wrote in message . ..
On 21 Jun 2004 09:05:57 -0700, (Meoww) wrote:

Phil Addison wrote in message . ..
My daughter's house has had a patch of damp appearing under the upstairs
windows since she bought the house 5 years ago from a builder (I did


big snip

I think you might be barking up the wrong tree here Phil.

It's almost certain that your problems are due to the outside
rendering and the poor detailing/workmanship of the window.

big snip two

It sounds like you're on the right track if you've sealed the cill.
The chances of it being porous are quite remote and if it is, you
could probably cure this with a water repellant.

It's difficult to envisage exactly what you've got but if you've
removed the plasterwork from the inside, you should be able to see if
there's a dpc there or not. However, if you can't see it, it could be
quite a major job to put one in and you're probably better going along
the sealing it all route.

Make sure water can't blow in from underneath and from the sides and
that's about all you can do. I presume you're making good these seals
with mastic?

From your description of where the wall is wet it certainly looks like
the culprit is the cill and not the wall.

Just don't re-plaster internally with a waterproof mix. Browning and
skim will do quite nicely for inside. If you haven't cured the problem
at least you'll be able to see its manifestations and not run the risk
of wet/dry rot further down! You may get effloresence until it all
dries out but wiping this off is easy and it'll stop when the
brickwork is dry.

Don't suppose you can post a photograph?

Cheers

Patrick

On 21 Jun 2004 00:38:51 GMT, (Andrew
Gabriel) wrote:

Cement goes back to roman times. However, prior to Portland cement,
it was more expensive, so it wasn't used for everything like it is
today.

Thanks Andrew for clearing that up. I haven't been able to get up there
on a ladder yet to have a closer look, but last time the sill material
looked pretty recent.

I think the only way the sill will be letting water in is if
there are cracks in the render.

If it IS rendered like yours!

If you stop the water entry and let it all dry out, you can use
pretty much anything (personally, I use bonding coat as the scratch
coat). However, none of the gypsom-based plasters are suitable if
it's damp.

I understand why you can't use these if it is permanently damp, but do
you mean you can't use them if there is still residual damp that is
expected to dry out through the plaster. In other words must it be
completely dry before using plaster as scratch coat?

Is that why cement render often seem to be used after damp treatment, so
that it can be applied straightaway to the still wet brickwork?

I have done a scratch (base) coat of cement (and lime if you like it)
and sand in a 1:1:6 ratio, with waterproofer added. Follow up 24 hours
later with regular plaster finish coat (no PVA required unless you
leave it much longer and the scratch coat has dried). The sand and
cement is very effective at keeping the water away from the plaster
finish coat. However, you'll probably need to let the wall dry out
first, at least so it doesn't feel and look wet.

Are you saying if it is not totally dry I should use that sand and
cement mix rather than bonding plaster as the scratch coat? What is the
problem if it is too wet; won't stick I suppose?

Phil
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On Mon, 21 Jun 2004 09:42:15 +0100, "stuart noble"
wrote:

[snippage restored for continuity]

On Sun, 20 Jun 2004 15:10:29 GMT, Phil Addison wrote:

On Sun, 20 Jun 2004 13:23:57 +0100, "stuart noble"
wrote:

Sounds like you have lousy sills which you should ideally replace

If you prefer to modify the existing, you need to get a flat surface,
preferably sloping away a fraction.

The 'concrete' they are made of does seem to be fairly soft, and no
obvious concrete-type gravel visible at the surface. I did wonder if I
might be able to grind them down in-situ to get a decent run-off slope.
We had our limestone frontage restored last year and the stonemasons
used an air chisel to rough it back and a stone rasp to smooth it. I
wonder if I might achieve similar on these sills with my small SDS
chisel and/or an angle grinder if its not too hard. Don't know where to
get hold of a stone rasp though.

Polyfilla Exterior filler is fairly easy
to use as a skim although I would use car body filler if you can face the
extra work.

By 'extra work' do you mean sanding it smooth after it has gone off?

That and polyester being generally sticky and difficult to work with.

Ahh, yes. See what you mean.

I had the impression that Polyfilla Exterior was not particularly durable
or perhaps I'm biased by the interior stuff.

As a skim, more durable than any cement based mix

That would make it prime candidate then - cheap, easy to apply and
durable then. Is your preference for body filler because of its better
adhesion to the sill? I must say I would not relish working with the
latter if an easier alternative would do the job.

Then you need to get something genuinely waterproof on there.
I'm not clear why you suggest both a skim and a waterproof paint.

Skim to get it smooth/flat and provide a better base for the paint.

OK.

Pliolite paint is good but any solvent based paint will be better than
conventional masonry paint, which is not at all waterproof IME.

That was my other question (see my reply above), so thanks - I will
avoid conventional masonry paint.

I'm not familiar with Pliolite though
- what is it?

A type of synthetic rubber I believe. Macphersons, Johnstones, and most of
the other trade outlets do it. Based on solvent naptha so not too
environmentally friendly.

Thanks, found Pliolite here http://www.eliokem.com/prod_coatings_plc.php

By 'any solvent based paint' is that as in ordinary gloss
woodwork paint?

Yep, although a matt might look better on sills. Mine are coated in red
oxide primer which is quite a good match for adjacent brickwork.

The adjacent walls are rendered in a yellowish spar, so a light colour
would be OK. Think I prefer the idea of a specialist paint for longer
life though.

Phil
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"Phil Addison" wrote in message
...
On Mon, 21 Jun 2004 09:42:15 +0100, "stuart noble"
wrote:

Not comimg in via the roof, the damp/water you are seeing ?

A friend of mine had a severe damp problem under the window cill of an
upstairs windows of an 1890's (I think) house. After much faffing, plaster
removal etc was traced to an "over generous" piece of roofing felt poking
(and loose/missing tile) into a gutter and diverting water into the brick
cavity. Water was running down the cavity, around the window frame, around
the cill and re-appearing on the brick work under the cill.

Fixing the roof/gutter problem stopped the damp.

On Mon, 21 Jun 2004 23:40:43 GMT, Phil Addison
wrote:

I think the tranlucent is more like a varnish colour. Another
possibility is a UV stabilised clear expoxy.

Is that 'paint-on' or spread as a skim?

Hi,

Probably best to put it on with a spreader and brush it out. Have a
look for epoxy concrete or driveway sealers for some examples. If it's
a concrete sealer it will need to have UV inhibitors.

Also it's better to seal around the window after the cill has been
sealed, most sealants stick better to a non porous surface, and if the
sealant starts to come away there's less chance of water getting into
the cill.

cheers,
Pete.

In article ,
Phil Addison writes:
On 21 Jun 2004 00:38:51 GMT, (Andrew
Gabriel) wrote:

Cement goes back to roman times. However, prior to Portland cement,
it was more expensive, so it wasn't used for everything like it is
today.

Thanks Andrew for clearing that up. I haven't been able to get up there
on a ladder yet to have a closer look, but last time the sill material
looked pretty recent.

So does mine;-)

I think the only way the sill will be letting water in is if
there are cracks in the render.

If it IS rendered like yours!

OK, or cracks in the casting;-)

If you stop the water entry and let it all dry out, you can use
pretty much anything (personally, I use bonding coat as the scratch
coat). However, none of the gypsom-based plasters are suitable if
it's damp.

I understand why you can't use these if it is permanently damp, but do
you mean you can't use them if there is still residual damp that is
expected to dry out through the plaster. In other words must it be
completely dry before using plaster as scratch coat?

The problem is if it takes weeks to dry out, as it well might.
That's long enough to damage the plaster. You end up with the
finish coat looking permanently dark (like it was wet), and the
rear turns to powder. You'll probably also get white powder salts
growing on the surface as the water carries salts to the surface
and evaporates leaving them behind (looks like white mold), but
that just brushes off. If the wall is decorated, it doesn't come
off so easily, and left in the decorations, I've heard it said
it can have a hygroscopic effect, keeping the area slightly damp.

Is that why cement render often seem to be used after damp treatment, so
that it can be applied straightaway to the still wet brickwork?

Maybe.

More likely is that because damp treatment usually doesn't work
because it's wrongly diagnosed, you have to make the finish
waterproof to hide the damp. Most damp treatment companies seem
to only have equipment for injecting a damp proof course, so the
only thing they're likely to diagnose is rising damp, which mostly
isn't the cause. The sand and cement render will project against
damp wall (unless it's soaking wet), without injecting it.

Another factor may be to prevent the plaster bridging the new
injected damp course. Sand and cement should be OK for this (as
always, assuming it has waterproofer added). It may not be possible
to inject low enough to avoid bridging by internal finishes due to
outside conditions.

I have done a scratch (base) coat of cement (and lime if you like it)
and sand in a 1:1:6 ratio, with waterproofer added. Follow up 24 hours
later with regular plaster finish coat (no PVA required unless you
leave it much longer and the scratch coat has dried). The sand and
cement is very effective at keeping the water away from the plaster
finish coat. However, you'll probably need to let the wall dry out
first, at least so it doesn't feel and look wet.

Are you saying if it is not totally dry I should use that sand and
cement mix rather than bonding plaster as the scratch coat? What is the
problem if it is too wet; won't stick I suppose?

I haven't tried when its very wet, but that might be an issue.
The suction might be non-existant, and the PVA coat might not soak
in to the brickwork (could dilute it less perhaps and hope it mixes
with the moisture at the surface).

--
Andrew Gabriel

On 22 Jun 2004 00:56:54 -0700, (Meoww) wrote:

Phil Addison wrote in message . ..
On 21 Jun 2004 09:05:57 -0700, (Meoww) wrote:

Phil Addison wrote in message . ..
My daughter's house has had a patch of damp appearing under the upstairs
windows since she bought the house 5 years ago from a builder (I did
warn her!)

big snip

It sounds like you're on the right track if you've sealed the cill.
The chances of it being porous are quite remote and if it is, you
could probably cure this with a water repellant.

Not sure about 'sealed', but I hope so. I sprayed them twice with stuff
sold for treating penetration problems in walls. Can't recall the name
at the moment.

It's difficult to envisage exactly what you've got but if you've
removed the plasterwork from the inside, you should be able to see if
there's a dpc there or not. However, if you can't see it, it could be
quite a major job to put one in and you're probably better going along
the sealing it all route.

Can't see it so far.

Make sure water can't blow in from underneath and from the sides and
that's about all you can do. I presume you're making good these seals
with mastic?

That is possible. I didn't put a bead under the sill or at the vertical
edge. Perhaps that would be a good idea. I used Unibond silicone from
B&Q, about £7 a tube.

From your description of where the wall is wet it certainly looks like
the culprit is the cill and not the wall.

Just don't re-plaster internally with a waterproof mix. Browning and
skim will do quite nicely for inside. If you haven't cured the problem
at least you'll be able to see its manifestations and not run the risk
of wet/dry rot further down! You may get effloresence until it all
dries out but wiping this off is easy and it'll stop when the
brickwork is dry.

I like the 'when' :-)

Don't suppose you can post a photograph?

Hi everyone. Hope these photos are useful. I took them yesterday.

This is the inside wall
http://www.pando.pwp.blueyonder.co.uk/Damp/Wall.htm
and these are some shots of the sill taken with camera poked through the
upper opener, and through the glass
http://www.pando.pwp.blueyonder.co.uk/Damp/Sill.htm

You can see the wall construction is a bit odd (in the tall edge-on
photo). The top 3 courses are not flush with the rest and protrude about
1/2" into the room. The 4th course from the top protrudes about 1/4".
That, and the different colour of the top 3 courses makes me suspect the
original sash went lower that the recent uPVC frame. The darker brick at
the top are also the dampest, but I think they might be getting slightly
drier now they have been exposed a few days. Heavy rain tonight should
be interesting but I don't expect to be able to get round there again
before the weekend.

Phil
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On Tue, 22 Jun 2004 13:50:38 +0100, "Ian Middleton"
wrote:


"Phil Addison" wrote in message
...
On Mon, 21 Jun 2004 09:42:15 +0100, "stuart noble"
wrote:

Not comimg in via the roof, the damp/water you are seeing ?

No. She has had an attic conversion which completely replaced the roof
over there, and it didn't cure the damp.

A friend of mine had a severe damp problem under the window cill of an
upstairs windows of an 1890's (I think) house. After much faffing, plaster
removal etc was traced to an "over generous" piece of roofing felt poking
(and loose/missing tile) into a gutter and diverting water into the brick
cavity. Water was running down the cavity, around the window frame, around
the cill and re-appearing on the brick work under the cill.

Fixing the roof/gutter problem stopped the damp.

Phil
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On Tue, 22 Jun 2004 18:23:16 +0100, Pete C
wrote:

On Mon, 21 Jun 2004 23:40:43 GMT, Phil Addison
wrote:

I think the tranlucent is more like a varnish colour. Another
possibility is a UV stabilised clear expoxy.

Is that 'paint-on' or spread as a skim?

Hi,

Probably best to put it on with a spreader and brush it out. Have a
look for epoxy concrete or driveway sealers for some examples. If it's
a concrete sealer it will need to have UV inhibitors.

Also it's better to seal around the window after the cill has been
sealed, most sealants stick better to a non porous surface, and if the
sealant starts to come away there's less chance of water getting into
the cill.

Hmmm... I've just realised that everyone seems to be assuming that the
sill is still porous. Don't forget I have given a very generous sloshing
with silicone fluid. I WAS hoping you'd all say that should be OK, but
the only comment on is from Andy saying his only helped a bit. Is it the
case you all think that stuff was a waste of time?

Pete, I did put the new silicone bead seal around AFTER treating the
sill. Guess it will have to come off again if I DO need to
paint/spread/skim with some other stuff as well.

Phil
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On 22 Jun 2004 23:08:51 GMT, (Andrew
Gabriel) wrote:

In article ,
Phil Addison writes:
On 21 Jun 2004 00:38:51 GMT, (Andrew
Gabriel) wrote:

Cement goes back to roman times. However, prior to Portland cement,
it was more expensive, so it wasn't used for everything like it is
today.

Thanks Andrew for clearing that up. I haven't been able to get up there
on a ladder yet to have a closer look, but last time the sill material
looked pretty recent.

So does mine;-)

;-)

I think the only way the sill will be letting water in is if
there are cracks in the render.

If it IS rendered like yours!

OK, or cracks in the casting;-)

I meant I'm not convinced it is that construction, but I haven't had a
chance to test it further for brick innards.

If you stop the water entry and let it all dry out, you can use
pretty much anything (personally, I use bonding coat as the scratch
coat). However, none of the gypsom-based plasters are suitable if
it's damp.

I understand why you can't use these if it is permanently damp, but do
you mean you can't use them if there is still residual damp that is
expected to dry out through the plaster. In other words must it be
completely dry before using plaster as scratch coat?

The problem is if it takes weeks to dry out, as it well might.
That's long enough to damage the plaster. You end up with the
finish coat looking permanently dark (like it was wet), and the
rear turns to powder. You'll probably also get white powder salts
growing on the surface as the water carries salts to the surface
and evaporates leaving them behind (looks like white mold), but
that just brushes off. If the wall is decorated, it doesn't come
off so easily, and left in the decorations, I've heard it said
it can have a hygroscopic effect, keeping the area slightly damp.

That makes sense.

Is that why cement render often seem to be used after damp treatment, so
that it can be applied straightaway to the still wet brickwork?

Maybe.

More likely is that because damp treatment usually doesn't work
because it's wrongly diagnosed, you have to make the finish
waterproof to hide the damp. Most damp treatment companies seem
to only have equipment for injecting a damp proof course, so the
only thing they're likely to diagnose is rising damp, which mostly
isn't the cause. The sand and cement render will project against
damp wall (unless it's soaking wet), without injecting it.

Oh aren't we cynics here :-). My daughter had two quotes from builders
before I got volunteered to look at it. First guy said to hack off the
plaster, and render it with sand/cement. He didn't notice apparently
that it was already done and the plaster skim so thin in places you
could actually eyeball the cement!! Second guy was sure it just needed
silicone fluid treatment outside.

Another factor may be to prevent the plaster bridging the new
injected damp course. Sand and cement should be OK for this (as
always, assuming it has waterproofer added). It may not be possible
to inject low enough to avoid bridging by internal finishes due to
outside conditions.

True. I suppose there are some outside conditions that can't be
rectified, but on here we would rectify them and not need the injection.

I have done a scratch (base) coat of cement (and lime if you like it)
and sand in a 1:1:6 ratio, with waterproofer added. Follow up 24 hours
later with regular plaster finish coat (no PVA required unless you
leave it much longer and the scratch coat has dried). The sand and
cement is very effective at keeping the water away from the plaster
finish coat. However, you'll probably need to let the wall dry out
first, at least so it doesn't feel and look wet.

Are you saying if it is not totally dry I should use that sand and
cement mix rather than bonding plaster as the scratch coat? What is the
problem if it is too wet; won't stick I suppose?

I haven't tried when its very wet, but that might be an issue.
The suction might be non-existant, and the PVA coat might not soak
in to the brickwork (could dilute it less perhaps and hope it mixes
with the moisture at the surface).

I see. I'm now thinking of leaving it open for a few weeks or till its
obviously drying before doing more.

Thanks again everyone for such excellent details.

Phil
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Phil Addison wrote in message ...
That would make it prime candidate then - cheap, easy to apply and
durable then. Is your preference for body filler because of its better
adhesion to the sill? I must say I would not relish working with the
latter if an easier alternative would do the job.
Body filler is also cheap if you get it from a car paint trade outlet.
Around a tenner for 3.5 kgs IIRC. It does have better adhesion and has the
advantage of being waterproof without being tacky.
However it is a bitch to use in this sort of situation. I find loads of
hardboard scraps useful. Use them as a base for mixing and as an applicator,
and chuck them for each mix. Only mix what you can apply in, say, 2 minutes
(which isn't a lot for detailed work).
A basic resin without filler (fibreglass resin) is very easy to use and has
the same benefits.

Thanks, found Pliolite here http://www.eliokem.com/prod_coatings_plc.php
The adjacent walls are rendered in a yellowish spar, so a light colour
would be OK. Think I prefer the idea of a specialist paint for longer
life though.
Johnstones had Magnolia on special offer recently ("Stormguard"), which made
it virtually the same price as standard masonry paint.
As an aside, it occurs to me that those cheap paving slabs are "concrete",
yet water goes straight through them.

Phil Addison wrote in message ...
Hmmm... I've just realised that everyone seems to be assuming that the
sill is still porous. Don't forget I have given a very generous sloshing
with silicone fluid. I WAS hoping you'd all say that should be OK, but
the only comment on is from Andy saying his only helped a bit. Is it the
case you all think that stuff was a waste of time?
'Fraid so. These products are usually siloxanes which, unlike silicone,
don't form a continuous film. They cure as microscopic pellets of
grease/rubber which can be dislodged by (although not soluble in) water.
Same stuff they use for dpc injection I think.

Phil Addison wrote in message . ..
My daughter's house has had a patch of damp appearing under the upstairs
windows since she bought the house 5 years ago from a builder (I did
warn her!!) who had done it up to re-sale. There was no sign of damp
then, it all being freshly decorated.


Hi

If the builder rendered the whole place that is something of a caution
sign. You dont generally render without good reason - although
unfortunately some fools do. Walls are often rendered when its too
much work to fix problems with them.


Assuming the sills are in fact concrete, my big question now is how do I
prove that it is (or is not) the sill before embarking on replacing
them.

You could just water proof them. I'm doubtful this would be achieved
with silicone fluid. Tarred surfaces stay waterproof far longer than
oil based paints and so on. You cant easily paint over tar though.

Any waterproof paint would do for a while, but really you want
something with good long life, as water penetration again would do a
lot of damage.

And ideally use internal plaster that lets any dampness dry, like lime
plaster. But only once the wall's properly dried.


More likely is that because damp treatment usually doesn't work
because it's wrongly diagnosed, you have to make the finish
waterproof to hide the damp. Most damp treatment companies seem
to only have equipment for injecting a damp proof course, so the
only thing they're likely to diagnose is rising damp, which mostly
isn't the cause. The sand and cement render will project against
damp wall (unless it's soaking wet), without injecting it.

Oh aren't we cynics here :-).

many are rather gullible unfortunately.


My daughter had two quotes from builders
before I got volunteered to look at it. First guy said to hack off the
plaster, and render it with sand/cement. He didn't notice apparently
that it was already done and the plaster skim so thin in places you
could actually eyeball the cement!! Second guy was sure it just needed
silicone fluid treatment outside.

I wouldnt expect either to solve the problem.


I wonder if I might achieve similar on these sills with my small SDS
chisel and/or an angle grinder if its not too hard. Don't know where to
get hold of a stone rasp though.

no


Hmmm... I've just realised that everyone seems to be assuming that the
sill is still porous. Don't forget I have given a very generous sloshing
with silicone fluid. I WAS hoping you'd all say that should be OK, but
the only comment on is from Andy saying his only helped a bit. Is it the
case you all think that stuff was a waste of time?

Penetration is liable to be patchy.


ust admit I tended to discount the external render because on the whole
face of the house there is damp coming through only under the sills of 3
windows (sorry, didn't mention the downstairs one before - that is only
a minor patch similar to the 2nd upstairs one). I imagine if the render
was duff it would come through in arbitrary places. But what you say is
quite possible, and I have rectified the useless seal between frame and
reveal and sill. The problem is finding out which of the possible entry
points is the cause.

There arent by any chance cracks spreading out from some of the
corners of the windows are there? If so, this picture might start
adding right up. 1890s, soft brick, rendered, cracks at window
corners, brickwork in poor condition under the render and wet:
classic.

If that is the deal, a possible explanation may be:

1. Mortar between bricks in such poor state that the wall begins to
move and crack
2. Bad mortar also allows driving rain to penetrate easily
3. Cracks start appearing in wall
4. Quick bodge fix for all of the above is to apply render.

The solution to this is to repair all the pointing - but there are
important caveats with that. If that is your situation do get some
more input before pulling render off, which may cause serious damage.


where should this dpc be? Directly under the sill I suppose. I don't
know if there is one. How can I find out? Good point though - if there
was a dpc it wouldn't matter if the sill was porous, right?

Any water penetration anywhere can be expected to freeze and slowly
disintegrate whatever its freezing in.



It sounds like you're on the right track if you've sealed the cill.
The chances of it being porous are quite remote and if it is, you
could probably cure this with a water repellant.

Not sure about 'sealed', but I hope so. I sprayed them twice with stuff
sold for treating penetration problems in walls. Can't recall the name
at the moment.

Sounds questionable to me.


I used Unibond silicone from B&Q, about £7 a tube.

try toolstation.com, something like 1.50 IIRC

Good luck.


Regards, NT

Phil Addison wrote in message . ..
On 22 Jun 2004 00:56:54 -0700, (Meoww) wrote:
snip

I'll taken even money you've cured it!

Another potential culprit was the actual seal of the window with the
cill but it looks like you've done that one too!

If your rain today was like our rain today, you'll know pretty soon
0))

Keep us posted

Patrick

p.s. do you do weddings too - excellent photos ;-)

On Wed, 23 Jun 2004 00:23:35 GMT, Phil Addison
wrote:

Hmmm... I've just realised that everyone seems to be assuming that the
sill is still porous. Don't forget I have given a very generous sloshing
with silicone fluid. I WAS hoping you'd all say that should be OK, but
the only comment on is from Andy saying his only helped a bit. Is it the
case you all think that stuff was a waste of time?
Hi,

Make a little 'dam' of blu tack on the cill, fill it with water and
see what happens.

Also might be worth pouring some water on the sill and checking any
runoff doesn't flow round onto the render beneath. Could be worth
treating those areas with silicone if you haven't done already.

Another possibility is that water is getting into the render next to
the window and soaking down past the edge of the cil, so it could be
worth treating those areas too.

Finally, if you've treated the cill itself with silicone you might
have a job getting anything else to stick to it

cheers,
Pete.

On Wed, 23 Jun 2004 12:29:39 +0100, "stuart noble"
wrote:


Phil Addison wrote in message ...
Hmmm... I've just realised that everyone seems to be assuming that the
sill is still porous. Don't forget I have given a very generous sloshing
with silicone fluid. I WAS hoping you'd all say that should be OK, but
the only comment on is from Andy saying his only helped a bit. Is it the
case you all think that stuff was a waste of time?

'Fraid so.

Had a look at it after some rain and was pleased to see droplets rolling
around on the sill. I appreciate it may not last very long though (any
estimates?)

These products are usually siloxanes which, unlike silicone,
don't form a continuous film. They cure as microscopic pellets of
grease/rubber which can be dislodged by (although not soluble in) water.
Same stuff they use for dpc injection I think.

Are you sure? I'm no chemist but once talked to the chemi-lab of the
makers of Solignum when I was injecting it as a dpc. They told me that
the stuff is not intended (indeed does not) fill up the pores of the
bricks, but coats the internal surfaces of the pores with a very thin
layer which changes the surface tension so that water does not rise past
it. The upshot of this is that you can repeat the treatment if the first
was inadequate.

See
http://groups.google.com/groups?as_u....demon.co.u k
for 1997 post.

Phil
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On 23 Jun 2004 10:35:49 -0700, (Meoww) wrote:

Phil Addison wrote in message . ..
On 22 Jun 2004 00:56:54 -0700, (Meoww) wrote:
snip

I'll taken even money you've cured it!

That's what I like to hear - fingers crossed eh?

Another potential culprit was the actual seal of the window with the
cill but it looks like you've done that one too!

If your rain today was like our rain today, you'll know pretty soon
0))

Keep us posted

Had a look at it after some rain and was pleased to see droplets rolling
around on the sill. I appreciate it may not last very long though (any
estimates?)

Patrick

p.s. do you do weddings too - excellent photos ;-)

No, I wouldn't dare. (*blush*)

Phil
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On Wed, 23 Jun 2004 22:11:41 +0100, Pete C
wrote:

On Wed, 23 Jun 2004 00:23:35 GMT, Phil Addison
wrote:

Hmmm... I've just realised that everyone seems to be assuming that the
sill is still porous. Don't forget I have given a very generous sloshing
with silicone fluid. I WAS hoping you'd all say that should be OK, but
the only comment on is from Andy saying his only helped a bit. Is it the
case you all think that stuff was a waste of time?

Make a little 'dam' of blu tack on the cill, fill it with water and
see what happens.

I like that idea - very neat. I've got a packet of plasticine left from
the 'glass-slip' condensation vs damp test. Wonder if that'll stick well
enough. If not I'll buy a pack of blutak (hate the stuff normally -
wrecks the wallpaper when the family get their hands on it!).

Also might be worth pouring some water on the sill and checking any
runoff doesn't flow round onto the render beneath. Could be worth
treating those areas with silicone if you haven't done already.

Another possibility is that water is getting into the render next to
the window and soaking down past the edge of the cil, so it could be
worth treating those areas too.

Yep, did all that, sprayed pretty much everything in site. The spray
that got on the glass was a bugger to get off though. Meths and lots of
elbow grease shifted it in the end. White spirit might have been better
but didn't have any on site.

Finally, if you've treated the cill itself with silicone you might
have a job getting anything else to stick to it

Doh... You mean like blutak or plasticene!!!

cheers,
Pete.

Phil
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On 23 Jun 2004 04:48:41 -0700, (N. Thornton) wrote:

Phil Addison wrote in message . ..
My daughter's house has had a patch of damp appearing under the upstairs
windows since she bought the house 5 years ago from a builder (I did
warn her!!) who had done it up to re-sale. There was no sign of damp
then, it all being freshly decorated.


Hi

If the builder rendered the whole place that is something of a caution
sign. You dont generally render without good reason - although
unfortunately some fools do. Walls are often rendered when its too
much work to fix problems with them.

Eeek. I'll do some exploratory drilling to check the extent of this.
Must say the brickwork under the patch I exposed is pretty ropey. I was
going to repoint it before plastering, ut maybe I should render it (with
no waterproofer additive) as well after all to bind it all together?
OTOH, it only has a few courses to self support just there.

Assuming the sills are in fact concrete, my big question now is how do I
prove that it is (or is not) the sill before embarking on replacing
them.

You could just water proof them. I'm doubtful this would be achieved
with silicone fluid.

Had a look at it after some rain and was pleased to see droplets rolling
around on the sill. I appreciate it may not last very long though (any
estimates?)

Tarred surfaces stay waterproof far longer than
oil based paints and so on. You cant easily paint over tar though.

I wasn't reckoning on tarring it - don't think my daughter would
appreciate that.

Any waterproof paint would do for a while, but really you want

any idea how long. As I say, it is done now with silicone, but I
anticipate having to redo it unless I put an overcoat of something on,
such as one of those recommended in this thread.

something with good long life, as water penetration again would do a
lot of damage.

And ideally use internal plaster that lets any dampness dry, like lime
plaster. But only once the wall's properly dried.

What is lime plaster?

More likely is that because damp treatment usually doesn't work
because it's wrongly diagnosed, you have to make the finish
waterproof to hide the damp. Most damp treatment companies seem
to only have equipment for injecting a damp proof course, so the
only thing they're likely to diagnose is rising damp, which mostly
isn't the cause. The sand and cement render will project against
damp wall (unless it's soaking wet), without injecting it.

Oh aren't we cynics here :-).

many are rather gullible unfortunately.


My daughter had two quotes from builders
before I got volunteered to look at it. First guy said to hack off the
plaster, and render it with sand/cement. He didn't notice apparently
that it was already done and the plaster skim so thin in places you
could actually eyeball the cement!! Second guy was sure it just needed
silicone fluid treatment outside.

I wouldnt expect either to solve the problem.


I wonder if I might achieve similar on these sills with my small SDS
chisel and/or an angle grinder if its not too hard. Don't know where to
get hold of a stone rasp though.

no

OK, have given up that idea.

Hmmm... I've just realised that everyone seems to be assuming that the
sill is still porous. Don't forget I have given a very generous sloshing
with silicone fluid. I WAS hoping you'd all say that should be OK, but
the only comment on is from Andy saying his only helped a bit. Is it the
case you all think that stuff was a waste of time?

Penetration is liable to be patchy.


ust admit I tended to discount the external render because on the whole
face of the house there is damp coming through only under the sills of 3
windows (sorry, didn't mention the downstairs one before - that is only
a minor patch similar to the 2nd upstairs one). I imagine if the render
was duff it would come through in arbitrary places. But what you say is
quite possible, and I have rectified the useless seal between frame and
reveal and sill. The problem is finding out which of the possible entry
points is the cause.

There arent by any chance cracks spreading out from some of the
corners of the windows are there? If so, this picture might start
adding right up. 1890s, soft brick, rendered, cracks at window
corners, brickwork in poor condition under the render and wet:
classic.

Well, there are some cracks around. I have already had to tie in the
gable end wall (not where these windows are) that was found to be
leaning out a bit when the loft conversion was done. I'll have a closer
look at the corners next week, but I don't think we are in this scary
scenario.

If that is the deal, a possible explanation may be:

1. Mortar between bricks in such poor state that the wall begins to
move and crack
2. Bad mortar also allows driving rain to penetrate easily
3. Cracks start appearing in wall
4. Quick bodge fix for all of the above is to apply render.

May well be, but with spar outside and *if* it is all rendered inside,
difficult to be sure.

The solution to this is to repair all the pointing - but there are
important caveats with that. If that is your situation do get some
more input before pulling render off, which may cause serious damage.

Absolutely. I have no intention of getting into that (I hope!).

where should this dpc be? Directly under the sill I suppose. I don't
know if there is one. How can I find out? Good point though - if there
was a dpc it wouldn't matter if the sill was porous, right?

Any water penetration anywhere can be expected to freeze and slowly
disintegrate whatever its freezing in.

Right. So a dpc under the sill is not the answer, so the sill must be
waterproofed.

It sounds like you're on the right track if you've sealed the cill.
The chances of it being porous are quite remote and if it is, you
could probably cure this with a water repellant.

Not sure about 'sealed', but I hope so. I sprayed them twice with stuff
sold for treating penetration problems in walls. Can't recall the name
at the moment.

Sounds questionable to me.

Just have to wait and see if it dries out, or the 'blutak dam' tells me
anything.

I used Unibond silicone from B&Q, about £7 a tube.

try toolstation.com, something like 1.50 IIRC

Thanks. Noted for next time.

Good luck.


Regards, NT


Phil
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Phil Addison wrote in message ...
Had a look at it after some rain and was pleased to see droplets rolling
around on the sill. I appreciate it may not last very long though (any
estimates?)
IME 6 months or so.

These products are usually siloxanes which, unlike silicone,
don't form a continuous film. They cure as microscopic pellets of
grease/rubber which can be dislodged by (although not soluble in) water.
Same stuff they use for dpc injection I think.

Are you sure? I'm no chemist but once talked to the chemi-lab of the
makers of Solignum when I was injecting it as a dpc. They told me that
the stuff is not intended (indeed does not) fill up the pores of the
bricks, but coats the internal surfaces of the pores with a very thin
layer which changes the surface tension so that water does not rise past
it. The upshot of this is that you can repeat the treatment if the first
was inadequate.
I'm no chemist either but www.sovchem.co.uk might give you some ideas.