Damp wall - what's causing it?

paintpot

Thanks BobProperty.

Ok, so if I seal the window which I was thinking and that doesn't solve it, the pointing does like fine, if it's the brickwork, which is single brick, what is the remedy for that then? I don't know what would be done to resolve that? Would rendering higher be the solution, maybe that's why the bottom has been rendered already because of historic problems.

Bungarm2001

We have several Victorian properties and every single one has had damp probs of one sort or another. They have all been fixed though...all it takes really is a bit of thorough investigation by looking for the obvious, then the not so obvious causes.

How long has the property been empty? When was the last time the central heating was on? Have you been at the property while it is raining to see exactly how the damp stain is spreading? (It's highly likely that your property has not a single skin wall, but a double non-cavity construction which makes it prone to penetrating damp from the outside. Is that what you mean by single wall?)

I agree with BobProperty, I think the pointing and window frame(s) need looking at. Also, the flaky masonry paint on the outside at the level of the damp patches is a bit of a clue.

Are the bricks now very porous at that point? If they have been repointed in the past with a mix that is too strong for the bricks, then this might be adding to your problems. You can see the results of using the wrong mortar mix by the state of the brickwork...the bricks will have eroded away in the weather leaving the stronger mortar mix practically untouched.

Steve_xx

I think that the window seems unlikely to be the cause of the problem due to the fact that the damp patch stretches as far to the right as it does.

I wonder about the rendering outside. Is it possible that the damp proof membrane may be breached by the rendering, thus water is travelling from the ground up the rendering and then leaching into the inner wall leaf? I know that you have stated that the damp is above the cill level but I wonder if this is due to the radiator being on and drying the lower section of the wall from floor to cill. Or, if the rendering is protruding in a ledgelike fashion it is possible that rainwater is running down the bricks and being absorbed by the rendering and then transferred through to the inner leaf.

Have you checked things at gutter level? Is the rainwater running through the gutter and not spilling down the walls? Also check that water is not spilling from the back of the gutters and getting into the cavity where it could be finding its way to the inner leaf.

You could try removing one of the outside bricks in the area and this would allow you to have a look at what might be happening. You might also consider replacing the brick with an airbrick and that in itself might help things.

paintpot

Bungarm and Steve, thanks vey much for your posts, you have both touched on things I have considered and need further investigation.

Bungarm, the property has only been empty since easter and the guy that lived there had the heating on permanently, it was like a sauna and I have kept the heating on alot to try and dry the wall out. My term about single wall it probably not technically correct, what I mean is I don't believe it has a cavity but structural things are not really my bag so you are probably correct in your thoughts. I have no history really about what work has been done on the property except to say I would could day with some certainty that the wall will not have been repointed in the last maybe 5 years. I can't tell if the bricks have erroded as they have painted but they seem sound enough as does the mortar but who knows what was used if they have been repointed. Yes the bricks do seem porous as when it rains you actually get little water bubbles on the internal paintwork which if you press then the paint comes off and it is visibly wet.

Steve, I would tend to agree with what you say about the damp stretching so far away from the window that it would seem the window is not the whole cause but could be a contributing factor. The rendering is protruding exactly as you describe and is like a ledge. The roof is not an old roof and have looked at the gutters which seem fine but still worth a professional opinion. I don't think the radiator is drying out the wall below the sill because also, the room next door which is the kitchen has a damp patch at the same height behind the boiler pipes and yet is isn't wet lower down.

So the two things that jump out, if the bricks are porous, what's the remedy for that then. The rendering could have breached the damp course so that's fixable but if it's the step in the rendering then I guess the rendering needs redoing higher? I have always questioned why the wall is half rendered, it suggests an historic problem perhaps.

Bungarm2001

Hiya

If it was me, I would firstly definitely look at the window carefully. Admittedly the wall is wet quite a distance away, but it could still be at least partially caused by the window leaking where it is fitted to the wall and the damp spreading by a 'wicking' effect thru the brickwork.

Next check the rendering carefully. Having a ridge where it's finished wouldn't help. Water is more than likely collecting there and spreading the same way, and I agree that the rendering was probably put there to try and cure a problem in the past where in fact it has just moved it.

You say that you are pretty sure that it isn't rising damp? Have you had the walls tested at floor level?

What is actually on the walls under the damp problem?

What I mean is, has someone in the past painted the internal wall with PVA or something similar to stop damp penetrating at a lower level? In my experience, using PVA in this way can make damp from the lower wall (possibly caused by a faulty DPC) simply be forced upwards to emerge higher up.

Have the wall thoroughly checked by a damp proofing firm and they might be able to come up with the real answer to the problem. Rendering the rest of the outside wall might be an option, but could make matters worse if it's not done properly.

paintpot

Hi ya

Thanks Bungarm. Definitely going to seal the windows. With the weather as it is with me at the moment, i.e. persisting it down with rain, I dread to see what the wall looks like come Tuesday when I am back there :eek: I didn't think it is rising damp, but I am no expert by any means and I haven't had anything tested yet. There seem so many possible reasons, I didn't really know where to start so wanted to get some ideas. I have a damp man I know so think I will get them round because I really want to find the cause rather than trying to cover it up.

The walls below the damp on the interior are plaster, the whole wall is plastered and no longer has wallpaper on. I confess, I have PVA'd the wall, only because the paint simply would not stick to the wall, it congealed, the PVA actually did the same which lead me to believe that someone has in the past treated the wall with something maybe to disguise the problem. I wasn't trying to hide the problem with PVA I just wanted to get the paint to stick to the wall because I wanted to see what would happen to it, but my PVA has not made any difference to the problem as it was back the following day even though the plaster was dry at the time of painting! The bottom of the wall remains fine though, just the strip in the middle that's the problem where the paint wouldn't stick. I have seen painted damp plaster before and it doesn't do to paint what happened to mine, you can easily paint damp plaster (of course you shouldn't) but this was something else, it was bizarre!

Bungarm2001

Has the property ever had a chemical, injection type damp proofing installed? You can tell if it has by a row of filled in holes around the outside approx 6-8 inches up from ground level

paintpot

Hi,

Yes it has.

Bungarm2001 wrote: »

Has the property ever had a chemical, injection type damp proofing installed? You can tell if it has by a row of filled in holes around the outside approx 6-8 inches up from ground level

Bungarm2001

Any chance you can contact the contractors who did the damp proofing or was it a DIY job?

paintpot

Hi

The history I do know of the property tells me it was a DIY job unfortunately.

I really appreciate your help bungarm. Any ideas why the paint would not take to the wall and congealed as everyone who has seen it has been baffled, my professional decorator who has worked on many houses of this age and type was totally thrown by it and said he had never seen anything like it.

thanks alot

Bungarm2001 wrote: »

Any chance you can contact the contractors who did the damp proofing or was it a DIY job?