Advice for repairing a damp wall in an old house
Discussion
I'm looking for some advice to help my Mum and Dad out. They live in an old house and one of the rooms has a damp external wall. The damp is coming in from an external hopper which takes water from an internal gully between two pitches. So the outside brick gets damp, and is north facing so never really dries. The walls are probably 2 feet deep so the whole wall must be damp. Historically the internal walls probably had a lime plaster or something breathable but sometime in the last 50 years it has been skimmed with some new plaster that doesn't look like it breathes in the same way. On top of this plaster is wood chip which has had many different coats of paint. Anyway, the plaster has blown and the wood chip paper is so damp it now just peels straight off. We have stripped off the damp paper, and pulled off all the loose plaster. Under the plaster is sand & cement which is kind of damp looking but doesn't really feel that damp.
So... the question is... what do we do next! We are worried that using a stain block on the sand and cement will just move the problem to the next spot. Equally we don't want to strip all the wood chip off because its a big room and 95% of it is fine. Is there a way to plaster the knackered bits and repaper it that wouldn't be inviting a repeat of the same problems in a few months time? Any ideas welcome!
Thanks in advance for any pointers.
Cheers, Klive.
So... the question is... what do we do next! We are worried that using a stain block on the sand and cement will just move the problem to the next spot. Equally we don't want to strip all the wood chip off because its a big room and 95% of it is fine. Is there a way to plaster the knackered bits and repaper it that wouldn't be inviting a repeat of the same problems in a few months time? Any ideas welcome!
Thanks in advance for any pointers.
Cheers, Klive.
klivedrgar said:
The damp is coming in from an external hopper which takes water from an internal gully between two pitches. So the outside brick gets damp, and is north facing so never really dries.
Job 1 is sort that out - it should be taking the water away from the wall, not passing it to the wall. Is the hopper or downpipe cracked or blocked? Photos?Once you've got that sorted, the wall will (eventually...) dry out. Heat and a dehumidifier will help.
The blown plaster's got to come off to help it dry out - it's coming off by itself anyway, so just give it a little assistance.
Thanks for the replies guys.
The hopper and downpipe etc are all fine, the problem is that they get blocked. In the past birds have nested in the hopper but we recently covered it in all manner of medieval spikes to put a stop to this. That will hopefully help but I think the reality is that fixing the problem is going to be tough. The internal gully is a complete PITA to access and it picks up the rainfall from two pretty big pitched roofs. What happens is that when there is a real downpour, all the moss, bird crap, twigs etc are pushed into the gully and then onto the hopper. Eventually, whatever we do, the gully and the hopper both have a day where they overflow. The lesser of two evils is to have the crap pushed into the hopper because at least that is accessible on ladders. The gully on the other hand is a major job to access. So.. other than doing our best to keep the hopper and gully as clear as possible.. we have accepted that this is a losing battle.
So with that in mind, whats the best way of doing the internal plaster and paperwork, with the knowledge that this wall is probably going to get wet again?
The hopper and downpipe etc are all fine, the problem is that they get blocked. In the past birds have nested in the hopper but we recently covered it in all manner of medieval spikes to put a stop to this. That will hopefully help but I think the reality is that fixing the problem is going to be tough. The internal gully is a complete PITA to access and it picks up the rainfall from two pretty big pitched roofs. What happens is that when there is a real downpour, all the moss, bird crap, twigs etc are pushed into the gully and then onto the hopper. Eventually, whatever we do, the gully and the hopper both have a day where they overflow. The lesser of two evils is to have the crap pushed into the hopper because at least that is accessible on ladders. The gully on the other hand is a major job to access. So.. other than doing our best to keep the hopper and gully as clear as possible.. we have accepted that this is a losing battle.
So with that in mind, whats the best way of doing the internal plaster and paperwork, with the knowledge that this wall is probably going to get wet again?
Ultimate answer is still to fix the hopper so the wall doesn't get wet, anything else will still give problems.
What I've done in the past with things I know get blocked it to control where the water can exit if the normal route isn't available. In this case I'd put in an overflow on the outside face of the hopper - maybe just a hole, maybe a small pipe - about half to two thirds up so it does nothing in normal situations but provides an exit if the hopper floods. This stops it over topping in an uncontrolled way and wetting the wall.
I'd also look at spacing the hopper off the wall slightly if possible.
What I've done in the past with things I know get blocked it to control where the water can exit if the normal route isn't available. In this case I'd put in an overflow on the outside face of the hopper - maybe just a hole, maybe a small pipe - about half to two thirds up so it does nothing in normal situations but provides an exit if the hopper floods. This stops it over topping in an uncontrolled way and wetting the wall.
I'd also look at spacing the hopper off the wall slightly if possible.
Edited by Jonesy23 on Thursday 23 November 19:22
Would fitting a larger outlet hopper help? This one receives 110mm pipe, like what you have for your soil pipes and may have less of a tendency to block up; have it discharge into a grated gulley at the bottom to stop crud entering your drains. It may look a bit unsightly/commercial but that's better than damp walls. 110mm hopper
Jonesy123 - a spout in the hopper is a great shout. Will give that a try. It will be a good early warning system if nothing else.
Wolfsonic, we have already upgraded the hopper a few times and its pretty big now with a 4" downpipe!
So if we can get this damp issue resolved, which will be awesome, is there any particular type of pva, or any type of plaster that we should use?
Wolfsonic, we have already upgraded the hopper a few times and its pretty big now with a 4" downpipe!
So if we can get this damp issue resolved, which will be awesome, is there any particular type of pva, or any type of plaster that we should use?
As has been said you need a hopper with a wier overflow so if it gets blocked it will still get water away from the wall. Personally I would say leave the interior to dry out which, if you’ve stopped the water penetration, it will. Then stain block and decorate.
During drying out the reducing wall dampness can reach the ideal for dry rot, so I wouldn’t introduce local heating to dry it out as it will increase the risk.
I always specify a velux in the internal pitch as access in these situations, even in new build
During drying out the reducing wall dampness can reach the ideal for dry rot, so I wouldn’t introduce local heating to dry it out as it will increase the risk.
I always specify a velux in the internal pitch as access in these situations, even in new build
If you're going to have to re-plaster the whole wall, I'd look into using something like a membrane system; if you are just going to patch a small area Google Vandex or Izonil plasters, they're often used for tanking out. You mention you've already got a 4'' rwp in place, could you fit a rodding eye in at low level then use drain rods to clear any blockages, save getting the ladders out, health and safety and all that?
I'd agree with fixing the issue. You mentioned moss on the roof that comes off and clogs the gully/hopper? Around here we stretch copper wire along the top of the roof and within a year it has stopped the moss growing but it might be easier to get someone in to spay the roof to kill it all now?
It's almost certainly the case that everything was fine until the roof developed debris etc so it makes sense to fix the core problem and everything else will take care of itself.
It's almost certainly the case that everything was fine until the roof developed debris etc so it makes sense to fix the core problem and everything else will take care of itself.
Edited by DonkeyApple on Friday 24th November 21:13
wolfracesonic said:
So lime plaster stops penetrating damp does it?
No but a membrane would be a disaster. You have to be extremely careful when using membranes or any form of complete dampness barrier particularly in these circumstances.
Once the cause has been sorted lime plaster could be an early finish if there’s still background dampness, or let it dry out and any finish could be used including the option of leaving as-is and decorating as I said earlier.
jason61c said:
wolfracesonic said:
So lime plaster stops penetrating damp does it?
No, the hopper will sort that. Lime allows any moisture that gets in the wall's, leave. Just as they were originally built/designed to.Anything else is just masking the problem and causing issues in time.
wolfracesonic said:
jason61c said:
wolfracesonic said:
So lime plaster stops penetrating damp does it?
No, the hopper will sort that. Lime allows any moisture that gets in the wall's, leave. Just as they were originally built/designed to.Anything else is just masking the problem and causing issues in time.
DonkeyApple said:
Why wouldn't you just clean the roof, spray it with a moss treatment etc and this deal with the actual cause of the problem and let the hopper get back to working and the walls gently dry back out?
The last bit yes it’s the way forward, but apparently he can’t access the roof pitches to do anything else at that level Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff