You needs somebody to have a look at it. The render might have been badly mixed leaving concentrations of cement that have run or despite what you say it might be fungus, what we often call mildew. If you have a 10 year guarantee and it is the former then the builder is responsible, but fight that one out, hmm-hmm. If it is fungal, which that new it should not be but does happen, then you need detergent and bleach to clean it off. Whatever you do, get advice first.
I see that this is quite an old topic but I am sure the problems do not go away.
Our house has a main Westerly facing wall. It has several windows both lounge and bedroom which we have just had replaced with uPVC double glazing due to the fact that the previous wooden framed ones had rotted.
We notice(d) that when we had a particular bout of heavy rain we had water ingress with water running down the interior walls and we assumed that this was due to the poor state of the old frames.
Even as soon as the new windows were installed the problem has not gone away and the water ingress happened again. We initially assumed that the the new windows had been poorly installed and we called the fitters back. We checked them together and even sprayed them with a garden hose which showed that they were not the problem.
We also sprayed water at the top of the wall, between the roof and eaves this again did not show any problem or water inside the house. The window fitter came up with one suggestion and this is were I currently am and I wonder if anyone else has had a similar issue.
He stated that the problem could be the render on the wall acting like a giant sponge and when the rain is particularly bad and coming directly from the West it soaks up the water which then gets through the wall and eventually drips, puddles inside.
The wall does have some discolouration and green, mossy areas particularly below the bedroom windows which I had put down to the previous rotten wooden frames.
He suggested cleaning and treating the wall.
So can anyone recommend a good wall cleaner? Can I use something similar to the stuff they use on the roof as seen in Brico? Any other suggestions.
After cleaning I then thought some sort of Polyurethane waterproof protective coating. Again does anyone have any recommendations or experience?
Having just spent several thousand Euros on the windows I do not want another major expense of removing and replacing all the wall render if there is a more simple cost effective solution…
The green mossy areas are on the outside wall I trust?
Apart from water running down the wall during rain - are there other symptoms - mould - stained plaster - plaster crumbly - paper peeling.
It would be “odd” if the render soaked up and then released as “running water” (having transferred through the wall itself - got through the plaster - paint/paper - if its modern gypsum plaster it would stain (very very badly)- lime would show some discoulration and you’d see symptoms all the time.
Is it just rain - or cold days? Water “running” normally means condensation - and quite a bit of it.
How olds the house?
But there’s never a simple solution to damp. First of all try and work out what the problem is. And don’t assume its “one” problem. Green walls is a never a good thing. And trying to block with coverings is just asking to spend a lot more 2 years down the line. Find it - fix it. If the outside render is green its ****ed anyway - rip that off and see if there’s anything obvious.
Render thats “old” and pulling away/cracking can trap water behind - but this would show as penetrating damp - stains - damp plaster - crumbly plaster. Especially bad if its concrete render
I would say - attempting to cover with things never works - it tends to make it worse. You just further trap the moisture and make fixing it properly more expensive.
If you don’t know what your doing (in the nicest way) get a builder in … not a window fitter. Anyone who says paint/seal/inject - say thanks and goodbye. Anyone who waffles about Lime and nothing else is also an idiot. The builder that says dunno until I take some render off / plaster off is the one to listen to. (The solution may include lime but it won’t be root cause)
But equally be careful its not a condensation problem - which visible water normally means- rainy wet weather tends to make air moist - moist air - cold wall will bring condensation. Old unlived in house - with leaks and crap windows may well be just “damp” and need heat/air over a few months.
Blocked or lack of guttering can cause damage too.