Damp Plaster Behind and Above Skirting Board

[WSB]

Hi,

Just trying to bounce some ideas around here and would welcome any ideas/suggestions.

Have noticed a problem recently but think it may be have been like this a while and gone unnoticed.

In the kitchen there is a patch of plaster on an internal wall behind and just above a short section of skirting board (now removed) which is slightly damp to the touch. Further above this, all is dry

I'm about to carry out further tests to confirm but currently I believe the problem comes about when we switch the central heating on.

This piece of plaster is to the left of a cupboard which used to contain an old boiler that we had replaced and moved 15 years ago.

Inside this cupboard is the central heating drainage tap and another piece of pipe crimped at the end. The piece of pipe crimped (literally just squeezed at the end) was like this even when the very old boiler was in place 15 years ago, so assumed it was just a very old disused pipe.

However, did notice tonight that this crimped end of pipe does get warm to the touch when the heating is on which is a bit alarming as the end isn't exactly sealed proper. Just squeezed together. That said, there's no sign of leakage or dampness there.

NB: There is no sign of damp on the wall inside this cupboard.

I'm concerned there's some pipe in the wall that's leaking, so before I go chiselling my wall away (which I don't fancy doing for fear of hitting a pipe), I thought I'd tell my story to this forum and welcome any ideas/suggestions???

Thanks all!!!

 

[terryplumb]

Quite possibly a pipe that's weeping.
Is your boiler / c/ heating pressurised ? If it is ,have you been experiencing pressure loss ?

 

[WSB]

Thanks Terry,
I'm pretty sure it's not pressurised. It's a 15 year old condensing wall boiler with open vent in the loft.
Had the cylinder changed a few months ago but don't think that's related.
Heating has been working well. No noticeable difference.
Weeping pipe makes sense although a pain in the backside.
We live in a hard water area and usually any weeping (e.g around gate valves) tends to seal itself. That said, assuming this is a central heating pipe, they'll be some pressure behind it when it heats up.
Contemplating carefully digging the wall away where it's damp....

 

[terryplumb]

Can you post pics of the area ?
Central heating pipe in wall would create heat / warm wall.
A cold water pipe the opposite.
Is rising damp a possibility?

 

[WSB]

Thanks Terry,
Have attached pics of damp wall and inside the old boiler cupboard.
In the latter pic, you can see the newer drain pipe and the crimped pipe, now painted over.
On the other side of the wall is a toilet with sink albeit about 1.5 feet away.
Have taken away the boxing around the pipes in there in case there was some leak but all looked fine.
What you said about damp was interesting as not far from that area of damp plaster we had quite an ant infestation last summer.
I did read somewhere, this usually happens in areas around dampness.
Not sure why there would be dampness other than through leaky plumbing as it's very much an internal wall.
The house is 1965 build and no signs of damp anywhere else.

 

[terryplumb]

Is the floor concrete ? The plaster looks like it's coming down very low ,and may bridge the damp course ?

 

[WSB]

Yes, floor is concrete.
What do you mean by "bridge the damp course"?
So dampness coming up via the plaster?
The different colours on the wall pic are the kitchen paint at the top and just plain plaster at the bottom (what was behind the skirting) with some paint flaked away above.
If I leave the skirting off, I think it stays dry as probably continually drying out.
Wedge the piece of skirting in place, then come back later to find it's damp behind.

 

[WSB]

The position of the problem is right in the centre of the house.
Don't know much about damp rising but is that still possible if in such a central position?

 

[terryplumb]

There would be a damp proof course within the mortar ,somewhere close to the first brick level above floor level .If plaster is taken down close to floor level it goes across the horizontal damp course. And moisture travels up the plaster.

 

[terryplumb]

Plaster should never be taken down to ground floor level ,for reasons stated above. That's why skirting is used to finish off/ cover the brickwork that would otherwise be visible.

 

[WSB]

Thanks.
That's interesting and makes sense but does plaster not always come down behind skirting boards?
How much gap would you say there should be from the concrete floor to where the plastering can begin?

 

[WSB]

As a good experiment, I can try chiselling off the damp plaster behind the skirting board and see if that fixes it.

 

[terryplumb]

As a good experiment, I can try chiselling off the damp plaster behind the skirting board and see if that fixes it.

Yes do that. Where is the mortar joint ? Plaster finishing above the mortar would be your target .
Hack some off and show some clear pics .

 

[WSB]

Hi Terry,
Two pics.
First with damp plaster chiselled away.
Second with a knife I shoved down the back. When knife pulled out it was quite damp.

 

[WSB]

Would I be right in saying that the fact I could shove a knife down there isn't a good sign?
Question is, is the damp at the bottom there all the time or only as a result of the central heating being on.
Need to do some more tests to find out whether the heating being on is a factor.
Have wedged some tissue against the wall about 2cm above the concrete base to double check it's definitely coming from the floor upwards and not from a low part in the wall. As I type though I think it'll be coming up though.