Damp wall - what's causing it?

BobProperty

Bungarm2001 wrote: »

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

Wouldn't matter too much, , I've never been impressed with injection DPCs and consider that the only reason they appear to work is the 1m of cement sand render on the inside wall that usually accompanies them. I take it this house doesn't have a cement sand render on the inside, up to 1m up the walls?
I also agree with Bungarm's earlier point about the mortar being too strong and damaging the bricks. Victorian houses would have been mortared with a softer mortar containing lime than the mixes which would be used today.

kb36

Had something similar in our kitchen and took us a while to figure it out. Damp proof specialists were called back and paid for a surveyor to help find cause of problem. Replaced guttering on the outside wall, painted on sealant to brickwork, resanded surface inside to see how patch was spreading etc etc. Eventually as a last resort builder knocked off all damp plaster work back to the brickwork (which was not damp) on the affected wall and discovered the wrong sort of plaster had been used. Re plastered wall - no problems since!!

paintpot

I have heard of "wrong plaster" and on a refurb quite recently in a stone cottage I had to get the plaster knocked off two meters high back to the stone and redone in a specialist plaster mix. However, I don't understand what dictates what type of plaster is required and in this house, as it had been converted into flats I can see that most of it has been replastered or at least this individual flat has which is an annex at the back and not the main house and therefore I am still at a loss as to why this is the only external wall affected when there is the bathroom, kitchen (although a bit behind the boiler pipes in the kitchen is affected which only has a partion wall separating it from the bedroom) and lounge are not affected.

I've dealt with some real issues on this house during the refurb but this problem is really annoying me :rolleyes:

kb36

'Wrong plaster' was on the internal wall - can check with my builder if you like. We always assumed - wrongly -that it was an external issue!

paintpot

I am willing to get as many ideas as possible as seem to be going round and round in circles. Obviously I want to fix the problem at the lowest cost but Iwant to fix it for the the long term. I don't want to rent it this with this problem, it's not how I operate. So I will fix the window which might contribute to the problem but don't think it is the whole problem I would fix the damp proof course which might contribute, fix the roof/gutters if they show any problems, fix the rendering etc etc. I will next week see what greets me, which I know will be really bad as it has rained, and then I think I need some specialists but all ideas have been....
VERY VERY GRATEFULLY RECEIVED :T I would love to know though, please anyone, if the bricks have become porous as has been suggested and seems a feasible problem, what the remedy is for that?

BobProperty

paintpot wrote: »

I have heard of "wrong plaster" and on a refurb quite recently in a stone cottage I had to get the plaster knocked off two meters high back to the stone and redone in a specialist plaster mix.

I'm guessing that it needed a lime plaster as the walls needed to be "breathable". i.e. allows some movement of moisture through the wall, which is how as a stone cottage it was designed to work.

paintpot wrote: »

However, I don't understand what dictates what type of plaster is required and in this house, as it had been converted into flats I can see that most of it has been replastered....

Has it just been replastered or has a render layer been applied when the damp course was done? It is possible someone has either got it wrong or done it with ordinary plaster (as it's cheaper) instead of cement sand render with waterproofer in it, which is what I recall being the usual "aftermarket" DPC system for a brick built house. Having said that, you probably can't tell without hacking off the plaster in a few small areas to check. Maybe you could tell by pushing a nail or similar tool (old screw driver?) into the plaster and trying to tell if there is a render under a top skim coat?
As for the bricks becoming porous, that's possible from damage from cracking and spalling (the face breaking off) resulting from re-pointing with too strong a mortar. It is also possible that the bricks aren't suitable for the job but that seems unlikely given it is a Victorian house. The solution would be replacement of the damaged bricks and repointing in the correct strength and type of mortar. I am suspicious that the wall is part rendered especially as that seems not to be an original feature.

BobProperty

Found this as a reasonable description of a specific commercial DPC product.
http://www.safeguardeurope.com/pdf_datasheets/rising_damp_book.pdf
Read the spec on page 18 onwards for the cement sand render part.

Also, are you sure this is a one brick thick solid wall and doesn't have a cavity? Cavities were put in some Victorian houses, it just didn't become a construction standard until 1919(?). A cavity full of rubbish left when the window was replaced or other work was done on the house could cause some damp problems.

paintpot

Edit, I have just read your link, it sounds ominous. What I am seeing and have seen is massive salt deposits I believe, powdery debris coming out both internally and externally. I reckon it's just been replasted with a bag of B & Q plaster and bob's your uncle - NOT!


I am not sure of anything on this property to be honest based on what I have found in 8 flats but anyway :rolleyes: I have knocked the plaster off internally and within an inch or so I am back to brick and it seems in very close proximity to the outside so would suggest it has no cavity but need to check this out as don't know how to tell The plaster on the walls is newish, I mean it had no paint on when I stripped the paper and I know that major redevelopment took place in 1993 but what anyone has done since then is anyone's guess :rolleyes: It looked like normal plaster to me having taken it off to check for consealed pipes which seemed might have been chased into the wall but that was a red herring and having seen other plaster and certainly other areas of the house have the old lime plaster for definite So in answer, from the inside, I reckon it's just been plastered onto brick. There have been many corners cut on this house and I am now finding them out but this has to be the worst of them all as I have an unrentable flat without possibly major costs with an undentified problem. The bricks seem to show no sign of deterioration but they are concealed by the render and the masonry paint and yes, the masonry paint is flaking but that it all I can see on the exterior. There are some abysmal bricks on the neighbours property but above and so I know what "shot" bricks look like but these seem fine and having done repointing elsewhere the mortar seems intact but this could have been done years ago with the wrong type. The property I would say has definitely been like this for some years.

BobProperty wrote: »

Found this as a reasonable description of a specific commercial DPC product.
http://www.safeguardeurope.com/pdf_datasheets/rising_damp_book.pdf
Read the spec on page 18 onwards for the cement sand render part.

Also, are you sure this is a one brick thick solid wall and doesn't have a cavity? Cavities were put in some Victorian houses, it just didn't become a construction standard until 1919(?). A cavity full of rubbish left when the window was replaced or other work was done on the house could cause some damp problems.

Bungarm2001

It's relatively easy to check how the wall was built, i.e. with a cavity or not by checking the thickness of your window frames (I can't tell from your picture) cavity walls are around 30cm thick, single walls around 23-25 cm if I remember rightly.

You mentioned that the affected room is an 'annexe?' do you mean it is an addition as in an extension or an original part of the building?

We have had properties where the original was Victorian with brick built additions in the 30's or even the 60's. Almost always the additon (or extension) was without a proper DPC and 'remedied' (hhaahaa) later with injection DPC which broke down after a few years.

Previous owners then tried to remedy the resultant rising damp by PVA'in g (or something similar) the interior walls and rendering the exterior with what turned out to be the wrong type of render mix. Combined, these two 'cures' caused the kind of penetrating damp you seem to be experiencing by forcing the moisture upwards.

You might be looking at removing and replacing both the interior plaster and the exterior rendering in the worst case scenario. See what your damp expert comes up with, but I wouldn't mind betting that the damp is originating from a dodgy DPC.

Please let us know how you get on...it's good to share all these trials and tribulations!

paintpot

Cheers Bungarm

I do believe the annex is orginal but I don't know the full history but judging by others on the streets everyone seems to have followed suit

There are actually two houses, I am refurbing, both next to each other and the one next door has a damp problem in the annex but in the upstairs room. However, each "flat" is laid out differently, one annex flat is one story and the other two storey. However the damp next door has been diagnosed by a damp specialist as condensation and I have remedial action going on there to remedy it but when the specialist came out I didn't have the keys to this flat so this problem has bitten me on the bum! The damp man assessed the DPC to be fine elsewhere except a slight damp patch in the ground floor front room where the step into the front door bridges the DPC. As annexes, at the back, they are very exposed to the elements and the properties have also in the past had serious subsidence which is now stable ( I could show you some amazing photos to show how wonky they are) but they also have not been cared for and bodged over the years which I am now sorting out. In the past, it was never a case of sorting the problem, I think it was a case of hiding/disguising/covering it up from what I have found to date so I am instantly suspicious - like why render half an annex and then paint the rest? Answer, cheapest cost, looks ok, hides a problem!

I will keep you posted, because once I find the problem and solve it I will be happy as once it's done I only have one flat left to finish