Weird internal damp problem.

[Sharpey]

Hi all.

Last September we had a damp problem in a section on our bay window. We had a damp company come in and take off the plaster, inject a chemical damp course, and replace the plaster with some sort of special damp plaster (not too sure of the exact name). They also re-built the plinth outside with a special plaster as well.

Everything dried out nicely, but in the region of the fix, a couple of random damp patches have emerged. I have scraped off the mist coat (which was a permeable, contract matt thinned down), gently dried with a heat gun, but an hour or so later the damp came back. A small amount of white powder emerged as well a fortnight ago although this was only once and not all over, just on a small bit near the bottom.

I have had the areas that were fixed checked with a damp meter and they are dry, the areas above and beneath all appear to be dry. Outside, there doesn't appear to be any damage that could indicate penetrating damp, no broken pebble dash, paint, guttering.

The damp company thinks it is residual damp finding the 'path of least resistance' and drying out slowly in the patches. Coupled with condensation they reckon this is why the wall is wet, and so to leave it unpainted and to dry for a few months.

Does anyone have clues to what could be the problem and any advice on what should be done? It's been a long slog doing this house up and not being able to paint two big walls right at the end is going to be a big frustration.

Here are pictures of the issue

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• Sharpey
• 7 Feb 2014
• 1

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• Sharpey
• 7 Feb 2014
• 1

Thank you for any help.

 

[jeds]

It could be residual. Masonry takes about a month per 25mm of thickness to fully stabilise. But equally is could also be what caused the original issue - i.e. water penetrating the junction between the house and the bay or around the frames. A bit of warmer dryer weather followed by a week or two of rain will reveal any problems so if that miracle ever does occur keep an eye on it then.

 

[ree]

Why not post pics of the outside wall and bay elevations esp. at "plinth" level?

Why did you have a "damp" problem in that area in the first place?
Did the Damp Company investigate and tell you why?

 

[Sharpey]

Alright guys. Thanks for your replies.

OK, here a couple of pics of the outside area on the other side of the damp patch.

The damp patch would be slightly higher than the window sill and to the right, by my estimation. Hope this is helpful.

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• Sharpey
• 7 Feb 2014
• 1

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• Sharpey
• 7 Feb 2014
• 1

The little patch to the left in the original post is an internal wall, of the porch area.

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• Sharpey
• 7 Feb 2014
• 1

I honestly can't remember what the damp company said other than rising damp. They speculated it could have been because of the old plinth, which they rebuilt.

 

[ree]

The plinth should have been removed, not re-made.

It is in ground contact and sucking up moisture - dark shadows of wicked damp can be seen.
The flat ledge topping the plinth is a water trap.

Until the plinth is eliminated no further investigations/speculations would be worthwhile on a web forum. But others might think differently.

If you read up on past posts around this "subject" you will have a much better heads up as to how the various kinds of damp interact with various kinds of construction, and how speculative remedial work can sometimes make things worse or transfer the problem(s).

 

[Sharpey]

Thanks for the reply, ree.

I see. The plinth was actually knocked off and rebuilt. Not sure if that makes a difference. It also has no coating (paint on it). There is no damp underneath the patch either, so if it was the plinth would it not be the case that it sucks up the moisture and migrates upwards, hence there being damp under the patch and not just randomly in the middle of the wall? That is probably a stupid question but I'm uneducated on these things.

Who would I contact for a second opinion? The more I read up on it, the more confusing things become. There seems to be a lot of guesswork involved and if you can't call up a damp company and trust their advice then who can you call?

 

[ree]

How could an injected damp course work when its immediately bridged by the re-built plinth?
What is under the pebbles?

Moisture could be splashing up from the sill, although there's no "green" splash marks on the render.

It could be condensation up against some cold spots. Condensation can manifest in many weird ways.

It could be some kind of moisture penetration at a higher level - we dont know if the walls are solid or cavity.

And it could be residual. Whats on the other side of the wall?

All speculation, including my comments, but until you begin eliminating possibilities there's no progress.

Independant Damp and Timber Surveyors are the way to go, ie surveyors who dont offer to carry out their own works - more expense but there it is.
I guess you could google for them in your area?

For the moment perhaps wait and see.

 

[jeds]

Thanks for the reply, ree.

I see. The plinth was actually knocked off and rebuilt. Not sure if that makes a difference. It also has no coating (paint on it). There is no damp underneath the patch either, so if it was the plinth would it not be the case that it sucks up the moisture and migrates upwards, hence there being damp under the patch and not just randomly in the middle of the wall? That is probably a stupid question but I'm uneducated on these things.

Who would I contact for a second opinion? The more I read up on it, the more confusing things become. There seems to be a lot of guesswork involved and if you can't call up a damp company and trust their advice then who can you call?

Just hang on for a couple of months. It is exceptionally wet at the moment and you might find a bit of drying weather will sort it out.

 

[ree]

sharpey,

If the Damp Company applied a hard coat remedial "plaster" then any incoming damp would be forced up, or sideways (interstitial movement) to beyond the hard plaster, to where it could emerge into the room.

If the above is correct, then the white stuff is probably chemicals from the wall carried out to daylight by the damp.

 

[Sharpey]

OK. Thanks for the help guys.

It could be condensation up against some cold spots. Condensation can manifest in many weird ways.

It could be some kind of moisture penetration at a higher level - we dont know if the walls are solid or cavity.

And it could be residual. Whats on the other side of the wall?

The wall is cold.

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• Sharpey
• 7 Feb 2014
• 1

As for what is on the other side, on that pic, right hand side patch is outside, left hand side is internal porch area. That wall is still cold though because the porch area is not as warm as the rest of the house. Pretty sure they solid walls, not cavity.

I am going to take you guys' advice, and leave it for a couple of months.

Appreciate all the help, until then

 

[Sharpey]

sharpey,

If the Damp Company applied a hard coat remedial "plaster" then any incoming damp would be forced up, or sideways (interstitial movement) to beyond the hard plaster, to where it could emerge into the room.

If the above is correct, then the white stuff is probably chemicals from the wall carried out to daylight by the damp.

All I was told is that the plaster allows the wall to breathe and resists salts or something. If what you're saying is correct, will it dry out on it's own or is it going to be another costly fix you think?

 

[gregers]

is it cavity?
if so why did they do a dpc from outside?
and if cavities were they opened up and cleaned out?.

 

[Sharpey]

From what I understand it is an old house and not cavity. I think it's solid brick.