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Hi all,
Looking for help from buildery types. Mate of mine has been trying to get someone to look at his house for ages, but hasn't been able to get anyone round. It's an Edwardian end terrace, probs about 1910. It has a big gable wall which has been rendered in sand / cement render (I think). Render is visibly cracked in some places. He's having massive issues with damp in the kids rooms, first floor, by the gable wall.
It sounds to me like it's water getting behind the render, possibly from the cracks, possibly coming down from higher up. It then can't evaporate and has nowhere else to go but in. My question is thoughts on what he should do next (apart from get a builder to look!). My feel is that cement mortar is totally wrong for this era of solid wall house. He needs lime mortar or something else breathable, or possibly nothing at all on the wall. I think he needs to have the render removed completely, then let the wall dry off over the summer. Then possibly rerender in something breathable. Or even external insulation.
Thoughts?
I have solved a few of these, not a builder but a part time property manager:
I am not a technical expert, but I've learned a lot, so these are the causes in my experience in order of what you should do:
1) Clean the mould off with bleach - once it starts it attracts more.
2) Check for water sources - I cannot stress how important this is, it would be number 1, but cleaning up is the first thing you should always do if there is mould. So are leaks coming from gutters, roof leaks valleys lead work etc, leaking water/heating pipes (internal or external, eg is there a radiator above?). Unused Chimney? I found these are double edged sword, people block them off and the rising air inside condensates and the damp comes through, or they are wide open and the rain comes in, and the flashing around them is normally crap. Best to cap with a rainproof vent. Obvs not if its being used for a fire or stove.
3) Ventilation - Humans make vast amounts of moisture indoors, so are you drying stuff in bedrooms, are rooms near kitchen or bathroom where moisture/steam is produced ? If so is there adequate ventilation, fans, windows, trickle vents etc. Windows should be opened for 10 mins a day minimum.
3) Salts - if there was a leak in the past then salts get washed through the bricks into the plaster, these are hygroscopic and absorb moisture onto the surface. I have found the only solution is to strip back to bare brick, wash bricks, dry for a week (or longer all summer sounds great) and plastered with a hard sand and cement render.(or lime if that's acceptable)
4) Do you use the heating? If tis cold you won't drive the moisture out...
5) Insulation - I have never really found this works, but that's what I am advised to do, I once dry lined a room with bad damp, on the advice of a damp proof guy, the mould came back on the new dry lining. It was fixed with trickle vents and stopping the tenant from using the radiators to dry his clothes.
6) Nuclear option - damp proof course issues , tanking is the best solution here, I found injections to be worthless. But you are first floor so its unlikely.
Damp
Needs more description of the problem than that. Is it wet on surface of the wall? Damp in wall measured by a tester? Crumbling plaster or mortar?
We have the classic issue of an old, narrow cavity wall that cannot be filled. So we have surface condensation in the room all the time, leading to mould and damp feeling plaster. Addition of insulated wallpaper has solved the surface and mould issue, but still the wall is cold and damp.
Not a cure, but a duhimidifier will help clear up all the symptoms and make the room nice to live in until a longer term fix can be found...
In the absence of further information I would concur with your 'feel'.
stonster you are describing a common problem, and describing the solution.
Also ventilation is needed. And if there is mould then do not use the room especially not if a childs room.
Also worth checking your gutters are clear.
Blocked/overflowing gutters can cause damp issues.
Is there a chimney at the gable end? We've had 3 of the 5 chimneys taken down oin the last year, all damp as buggery. Also try to keep furniture off the exteranl walls, wardrobes etc, ventillation is your friend, and agree re the dehumidifier.
Do all of this, then see how bad the problem is, but it sounds like some advice is required (not necessarily a builder though, tbh)
Some good responses, just like to add that last damp I found was quite a way from the problem. It was a slipped tile, disintegrated roof membrane, the leak was travelling along joists and once it's found a route it sticks to it.
I bodged a repair to buy time but best solution is a whole new roof.
Had this in my victorian flat years ago - gable solid wall, pointing was fine. Solution as above was to hack off the normal plaster and replace with sand and cement render internally.
Cavity walls were introduced to prevent this problem in the 1920s.
This kind of problem is very very common on older properties. It makes up a large proportion of our work (Lime harl/renders, lime pointing,masonry and traditional building).
Your suggestion that rainwater ingress via the cracked render is exactly what can happen, however, first thing to do is also check anywhere else where rainwater can enter the building and that internal ventilation is sufficient. This could be failed joints on the skews (assuming you have skews), failed haunching along the skew/roof joint, haunching around the chimney cans and chimney/roof interface. The roof generally. Is the chimney capped? Ideally with an elephants foot or china-man's cap which will allow ventilation while preventing rain falling into the flue. Lastly check the gutters and downpipes are all running correctly, are not blocked or leaking. It is staggering how many clients are adamant the rainwater goods are all fine on their house, when five minutes on a rainy day prove otherwise. I have even watched rainwater run down a poorly fitted tv aerial cable, bridge the gutter and then soak the wall below.
As far as the render is concerned, typically we would remove all the cement back to original mortar, daub out the wall and then harl with a hot lime mortar. Finally limewash, minimum of 5 coats. Once the cement is cut off the wall, drying of the underlying masonry can be pretty quick - the last harl job of 2020 went from 80% to 50% humidity in the room adjacent to the gable in 3 weeks. The internal wall of the room was exposed stonework and not lined, even so that is very quick. Not surprisingly the atmosphere of the room (and smell) was transformed. What was a visibly wet wall is now completely dry.
You could of course gun off the cement render and leave it to dry out over the summer, and a few clients do this themselves to save money - it's what I would do if I wasn't a lime harling contractor or I lacked cash for the whole job. Long term though, you are going to have to do something as you'll basically be left with a gable wall with pretty shoddy pointing. There's also a reasonable chance some immediate repair work will be required to the masonry such as a hole in a flue. Options would then be to repoint or re harl using an appropriate lime mortar. Depending on how exposed the gable is would sway your decision, as well as cost (pointing cheaper).
I have had a condensation issue on a north facing wall before now as it's a bedroom it's very humid.
Is the patch behind any furniture or on a random patch?
Need more info as suggested.
1) As mentioned, a cracked cementitious render, will suck water in through capilarity thus wetting the masonry which won't be able to 'breath' and readily dry out again because of said render. Around windows in rendered properties, you often find some damp even if it isn't enough to cause a visible problem like mold, for example. My house is afflicted with this to a minor degree.
2) It could be that the orientation/exposure of the gable wall is exacerbating the problem? Does it see much wind-driven rain?
3) Is the damp around a window like at the reveals or sill area? It may help to reseal the window frame externally. Is the external sill made of masonry or is it PvC with the window as a 'system'? If the latter it may need resealing against the render.
4) Are there any faulty water-goods leading to water cascading down the wall or otherwise bespattering the wall? This would be very bad. Unlikely on a gable wall but also check the condition of the verge to make sure nothing is missing or in disrepair there.
5) Hacking off the render is prima facie an appealing idea but it can also lead to brickwork/masonry becoming damaged; the render can something be so well bonded to the brick that the brick skins comes away too. One also doesn't know exactly what one will find. As suggested, almost certainly prepare to re-render with something lime-based or more modern polymers.
2 things raise my suspicions that this is condensations - 1. it's the gable end and gable ends are really prone to condensation as they act as large radiators wicking the heat out into the atmosphere. and 2 - the thread's been started during a cold snap. does the damp appear after cold rather than rain? does the damp appear in corners? if yes then i'd bet condensation. fix would be insulated plasterboard on the damp wall - a lot cheaper than scaffolding a chimney breast...
Thanks for all your useful thoughts everyone.
Update - builder has been up on the roof and says the flashing around the chimney is really bad so likely to be leaking. So could be that as well as the render. Oddly though, the damp comes through in the kids' bedrooms at first floor level, but they don't see any evidence at second floor. It does seem to be mainly around the chimney, which might well rule out condensation. There's no windows in the wall and it doesn't seem to be worse in cold weather, just wet weather!
Mate says the plaster near the ceiling in the kids' room just crumbled away, and this is on the inside wall of the chimney in their room, so not the outer gable wall (if that makes sense)!
Can water run down a chimney then into a room not at the top? Can it run onto the inside wall? That could well explain things, since it's pretty damp...
had it in my lad's bedroom. End terrace, so only one exposed wall which gets the weather and although the tile verge needed repairing it seems to have been the acquisition of a small room dehumidifier that has really reduced it.
As well as the cold spell, the fact he's in there for 20 hours a day currently for schooling, sleeping, and also doing whatever teenagers do in their rooms I think has vastly increased the amount of teenage breath, sweat, and general oomska that was condensing in that cold corner.
Had this in one of the attic rooms albeit without a rendered gable end wall. Old unused chimney breast in the room but the stack has been long gone on the roof.
In the end we’ve put a whole new roof, membrane, soffits and barge boards on the end of the house as well as having the mortar repointing. Bloody expensive but the house is now ready for water based Armageddon.