8 Jan 2008
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United Kingdom
Hi all - some advice /thoughts needed.

I have posted on here in the past about problems with my plastering/paintwork on one wall within the living room - which the consensus was efflorescence (Hope I got that right). So solutions were offered all of which started with "find the cause of the damp".

I have set out the situation below and would welcome advice/guidance on how to identify the source of the damp.

Thanks in advance.

The wall is externally facing stone built and about a foot and a half thick. The inside is plastered and painted. There is a window across a large portion of the wall with 2 stone mullions in it. There is an external door about 3/4 of the way across.

The damp problem (as I will call it) covers the length of the wall from the left hand side up as far as the door, but NOT on the small portion of wall to the right of the door.

It covers the inside facing of the wall in large patches, on the recess which house the windown and the gap between the window and the door.

It does not extend above the window, but in the gap between the window and the door it raises to about head height.

Possible causes of the damp I have considered:

1 - Leak from pipes above - however I have lifte floorbaords and all was dry - no apparent leaking pipe.

2 - Condensation from shower (Bathroom is at the top of the stairs which come down to the left hand side of this wall - thought damp air could be hitting the cold outside wall and causing the damp) however I have bought a decent sized dehumidifier and the problem has not alleviate. Also I would expect the problem to be as bad in teh bedroom directly above where the same situation would apply - it isn't.

3 - Rising damp (fits as it does not extend above the window) but there is a waterproof membrane built into the wall visible form outside.

4 - No ventilation in wall - No idea given the material and thickness of the wall if it as a cavity or not - the wall is very cold to touch.
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Do you know what the exterior stonework is?
If the wall is cob built involving exterior stone, rubble, then interior brick/stone construction then you have a problem as you cannot be issued a guarantee on DPC injection on this type of construction unless the interior plaster is removed and something like an Oldroyd Membrane is affixed to the interior wall before plastering.Check out Safeguardeurope.co.uk for their solutions. Very much sounds like you have a active rising damp problem.
I think, even if the original cause of damp is cured, hygroscopic salts in your plaster will need it to be removed.
See pics attached - having looked through pics of rising damp online it does not look the same as I have - but that may just be wishful thinking on my behalf.

Apologies for quality of pics (cameraphone done after dark) but it shows the height it reaches in one particular area where the clock is - which is in one streak about a foot wide from near a plug socket about a foot off the floor to almost right up to the ceiling.

To the left of the pis by the window there is little evidence lower down adn it is rife around the window all the way up to the ceiling.

There is no mould - just plaster bubbling and salts leaching.

Further thoughts appreciated.




Also no real deterioration for last few months (even over winter) althugh some spots have continued to leach salts. Most of the damage was done early last year and arose over about 6 month period.

Also aware I need to get replastered - hopefully an insurance job - but we'll see.
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The most likely culprit is 'condensation' more specifically 'interstitial condensation' - cause warm moisture laden air coming into contact with a cold surface/material. Vapour pressure allows the vapour present in the air to pass through the surface paint coating and the vapour will be then be condensating around the plaster/brickwork interface which develops the salt crystals / efflorescence that you are encountering, which then develops and interacts with the paint film in the manner shown in your last photograph.

Looks worse than it is - solution, well not that easy - my advice would be to insulate the external facing wall with a foil backed PIR insulation with integral plasterboard finish, thickness of insulation will depend on how much space you can afford to lose. Benefits foil has an extremely high vapour resistivity compared to other materials and you get the benefit of some heat being reflected back and you reduce heat losses through the wall thereby reducing your heating bill and carbon footprint. Even a 25mm thickness of PIR insulation + thickness of plasterboard would be better than nothing.

Thanks chaps - some good stuff there - condensation would be my call as the lessening of the deterioration has shown up with the use of the dehumidifier.

Going to get the bathroom vented with extractor above the shower - currently just a window to vent.

Is there a way of "proving" that is the problem so i don't just "solve it" and repair only for the problem to reoccur?

Pics of outside as requested - as no evidence of "rising damp" on the outside




There's no obvious signs of penetrating damp, so condensation looks the likely culprit.
When did you have those windows installed? They look quite new.

Do you have trickle vents? If you have, keep them open.

I'd want to avoid sealing an old structure.

What is that on the ground outside?

Have you raised the ground level? If that is a DPC between the first and second courses, it looks too close to the ground to stop splashing. I'd want 2 clear courses below the DPC before getting down to ground level.

When was that drystone wall built?
Windows were installed before we bought the property - i think about 8 years ago.

These are the only windows in the property without trickle vents. This is where the damp is - another thing that makes me suggest condensation.

Ground outside is rubber matting for kids play area - this was installed after the damp appeared. Other than this - which is about half an inch thick ground level not been raised.

The ground slopes, so it is indeed just above the first course at the highest point - any way to seal the bricks to avoid splashing effect - worth doing?

Drystone wall again after the damp appeared. Fairly recent - less than a year.

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