Help with my damp spot, please
Discussion
Hey all,
I've read a few damp spot threads recently with keen interest and it must be the time of year when these problems materialise.
With that in mind, I have a damp spot problem in my bathroom. I am really hoping someone can help me at least identifying which sort of tradesman I need to get in touch with to help diagnose the problem or maybe offer some diagnosis given my limited description.
The house is a 1900s miner's cottage at the end of a 10-house terrace. The main house is of a stone solid stone construction (lias stone) and the bathroom is an additional two-story construction built in the same style as the rest of the house. Half of the kitchen sits under the bathroom and the rest of the kitchen is an additional single-skinned and single storey extension built later than the rest of the house. The bathroom has a chimney stack but there are no visible pots or holes and there doesn't appear to be a chimney breast inside the bathroom or beneath it in the kitchen.
The bathroom is an oblong shape (2.4m X 3m), with the narrowest end joining it to the main house. The chimney stack is on the furthest away wall with a window in the back left-hand side of the bathroom. This is the only window in the bathroom. The roof was replaced fairly recently (in the last 5-years, done before we moved in) and the pointing and tiles all look fine and there's a felt layer underneath the tiles. The window was replaced earlier this year with a like-for-like double glazing unit but we specced a trickle vent that is always open. There's also an extractor fan that runs when the light is on and for ~5 minutes after the light has been turned off.
The damp problem is happening in the back left hand corner of the room on the ceiling and between the roof and wall (gable end - where the window and chimney is). The damp happens on both the longest wall and the end wall and looks like it originates from the top of the wall and then 'drips' downwards towards the floor.
Damp is present regardless of the outside weather but gets worse when it is either cold or wet. During this summer's long dry spell the damp spot decreased significantly but didn't dry out. This has led me to rule out it being a problem with the chimney stack, pointing, stonework or roof - ie there isn't a leak.
I run a dehumidifier underneath the damp spot 12 hours a day and it does a good job of drying out the night's damp. Take a shower and the damp spot will return instantly even with the window open, extractor fan on and dehumidifier running.
Note the darker spots of damp.
What on earth could the problem be? Any help is really appreciated!
I've read a few damp spot threads recently with keen interest and it must be the time of year when these problems materialise.
With that in mind, I have a damp spot problem in my bathroom. I am really hoping someone can help me at least identifying which sort of tradesman I need to get in touch with to help diagnose the problem or maybe offer some diagnosis given my limited description.
The house is a 1900s miner's cottage at the end of a 10-house terrace. The main house is of a stone solid stone construction (lias stone) and the bathroom is an additional two-story construction built in the same style as the rest of the house. Half of the kitchen sits under the bathroom and the rest of the kitchen is an additional single-skinned and single storey extension built later than the rest of the house. The bathroom has a chimney stack but there are no visible pots or holes and there doesn't appear to be a chimney breast inside the bathroom or beneath it in the kitchen.
The bathroom is an oblong shape (2.4m X 3m), with the narrowest end joining it to the main house. The chimney stack is on the furthest away wall with a window in the back left-hand side of the bathroom. This is the only window in the bathroom. The roof was replaced fairly recently (in the last 5-years, done before we moved in) and the pointing and tiles all look fine and there's a felt layer underneath the tiles. The window was replaced earlier this year with a like-for-like double glazing unit but we specced a trickle vent that is always open. There's also an extractor fan that runs when the light is on and for ~5 minutes after the light has been turned off.
The damp problem is happening in the back left hand corner of the room on the ceiling and between the roof and wall (gable end - where the window and chimney is). The damp happens on both the longest wall and the end wall and looks like it originates from the top of the wall and then 'drips' downwards towards the floor.
Damp is present regardless of the outside weather but gets worse when it is either cold or wet. During this summer's long dry spell the damp spot decreased significantly but didn't dry out. This has led me to rule out it being a problem with the chimney stack, pointing, stonework or roof - ie there isn't a leak.
I run a dehumidifier underneath the damp spot 12 hours a day and it does a good job of drying out the night's damp. Take a shower and the damp spot will return instantly even with the window open, extractor fan on and dehumidifier running.
Note the darker spots of damp.
What on earth could the problem be? Any help is really appreciated!
SpeckledJim said:
No expert but are those roof tiles fitted with the correct overlap?
Looks like the shapes on the sides are designed to be ~4 inches closer together?
The last row is only overlapped by an inch, is that correct?
Yeah, I originally thought that but there's quite a bit more tile underneath and that lack of overlap is only along the edge where water *shouldn't* be running...Looks like the shapes on the sides are designed to be ~4 inches closer together?
The last row is only overlapped by an inch, is that correct?
SpeckledJim said:
Hmm, that's not as bad as I thought, but its still very different to the other side of your roof.
Yarp, the roof isn't symmetrical.The reason I think it's a damp spot is that rain doesn't make it worse and a lack of rain doesn't make it better. For example, if we were to take no showers or use the bathroom at all for a few days but it rains buckets, the damp patch does start to fade slightly. I happens as soon as we create steam, humidity and heat in the room.
-Edited for accuracy of roof tile count!
Edited by BackPedal on Friday 9th November 15:59
wilksy61 said:
Out of interest where does your extractor fan exit to, I'm assuming its that grey mushroom thing however i have been in the ventilation industry for some years I've not seen that before at the very least it should have either a cowl, flaps or a grill.
https://www.domusventilation.co.uk/ventilation-sol...
Yes, it goes into the mushroom thingy. It looks kind of like a bell housing?https://www.domusventilation.co.uk/ventilation-sol...
The top of it siliconed against the wall but the bottom is open and air is free to circulate.
wilksy61 said:
I would suggest that you are getting very little airflow through that as the resistance will be quite high even over such a short run, also is the fan ducted through the wall with pipe or has somebody used flexi pipe .
Probably nothing to do with your issue however if it is present after a shower/bath then something is definitely damp
Not sure, I'll check tomorrow - but thanks for the suggestion.Probably nothing to do with your issue however if it is present after a shower/bath then something is definitely damp
wilksy61 said:
As a side thought running a dehumidifier with a window open will make the unit run a lot harder as it will basically draw air in from outside, you really should close windows when using one.
Yeah, I don't run the dehumidifier with the window open, just the trickle vent remains open.Edited by BackPedal on Friday 9th November 16:19
wilksy61 said:
It could do as you say its returns instantly after a bath as it has probably never dried out, never underestimate moist air - in most builds people use flexi pipe to extract from bathrooms going into the loft space and then outside. This should really have a condensation trap fitted as the cold loft air will condense with the warm moist air from a bathroom, I designed the one that Domus sell but they are very rarely used.
So should the extractor going through a wall like this have a condensation trap too?If I replace the grey mushroom thing with one of these or similar, could that really help?
foxoles said:
Whats the inner wall construction? Plaster straight onto the stone/brick would indicate cold wall condensation IMO even in summer. But it looks more like a leak except you say it's no worse in wet weather.
Plasterboard ceilings really wick moisture if touching a damp wall surface. Where is the dampest spot - in the corner join or higher?
Not entirely sure but I believe it to be paster directly onto the stone because the wall isn't very straight or flat which makes me think that it hasn't been dry lined or that there isn't plasterboard in there. One of my next steps was to drill a hole in the wall to see if I could see how it's made.Plasterboard ceilings really wick moisture if touching a damp wall surface. Where is the dampest spot - in the corner join or higher?
As for the dampest spot, it's right in the corner of the wall, not on the ceiling... I think!
Thanks!
Ricky146a said:
Even though the dampest spot might look like the corner, I think the 'leak' is at least as high as the top of the extractor.
The rest of the damp is just a result of the water running down the plaster in my opinion.
How long have you had the damp patches for?
They've been there since we moved a little over two years ago. But, the house was unoccupied for 6-ish months before we bought it and when we viewed it there was no damp in the bathroom and day we moved in there was no damp either. It's directly related to living in the building. Likewise when we go away, on return the damp has all-but gone.The rest of the damp is just a result of the water running down the plaster in my opinion.
How long have you had the damp patches for?
I'm going to get up there tomorrow with a ladder, check out the roof tile for cracks thoroughly, check all of the pointing for cracks and seal as necessary. I'm also going to dismantle the extractor fan and check out what is going on there.
wilksy61 said:
If you do have a pipe going through the wall then it should have a very slight slope downwards, if it has flexi pipe then replace it with pipe, and yes the cowl from B&Q is fine although the flap will tap when the wind is in the wrong direction, much better is a grille with a flyscreen.
Can’t say it will help you damp spot but it will certainly make sure your fan is extracting.
Going straight through a wall won’t been a condensation trap.
Thank you, I will look for a non flappy cowl - that's the end of the building the wind hits so I imagine it'll be quite noisy.Can’t say it will help you damp spot but it will certainly make sure your fan is extracting.
Going straight through a wall won’t been a condensation trap.
Thanks again!
Edited by BackPedal on Friday 9th November 18:33
Lemming Train said:
A bit of a left field angle here but have you checked for possible pipework in that vicinity that may be buried in/behind the wall? A lot of older properties have the water tank in the loft, for example. 
Also those roof tiles look all to cock to me but I'm not a roofer so could be talking out of my arse. If it's an external leak you're not forced to see deluges of water running down your internal walls when it's raining outside either. I had a broken chunk of cement just under the edge of the roof tiles on the gable end of an old property and it could be absolutely chucking it down and the rain wouldn't make it inside, yet if the wind direction was the 'other' way (and didn't need to be much more than a light breeze), the rain would run down the inside wall of the loft like a stream. In short : don't rule out it being an external leak just because it doesn't get any worse when it's raining as it could be a red herring.
Imo that's not room condensation from using the bath/shower. There's far far too much water there.
Ha, yes... there is pipework in the floor at that end of the building but it has been capped at floor level. I, too, thought that it could have been a leaky old pipe but turning the water mains off did as much good as not using the shower in the room for a few days. There was an old header tank in the house but it's long gone and the space it left is currently full of nice dry towels. I'm guessing that if there was any remaining pipework there wouldn't be enough residual water in them to keep this wet for two years!Also those roof tiles look all to cock to me but I'm not a roofer so could be talking out of my arse. If it's an external leak you're not forced to see deluges of water running down your internal walls when it's raining outside either. I had a broken chunk of cement just under the edge of the roof tiles on the gable end of an old property and it could be absolutely chucking it down and the rain wouldn't make it inside, yet if the wind direction was the 'other' way (and didn't need to be much more than a light breeze), the rain would run down the inside wall of the loft like a stream. In short : don't rule out it being an external leak just because it doesn't get any worse when it's raining as it could be a red herring.
Imo that's not room condensation from using the bath/shower. There's far far too much water there.
As for the rain direction, the side with the damp/leak is the west-facing side of the building and we get all of our prevailing weather from that way. If we get an easterly or northerly it doesn't dry out. But I am going to investigate water ingress further thanks to everyone's advice. As it happens, with the right conditions our flat kitchen roof leaked in just the way you described - it would stream down the inside of the building and was actually getting in through a crack in the pointing!
WyrleyD said:
Also, if it's raining and the wind is in the right direction then I guess water could get blown over the top of that fascia board collect on top of the wall then run down the inside when there's enough of it. Don't underestimate wind and rain, we had a very small hole in the render on the north face of our house up near the roof and during a particularly wet and windy spell we had water dripping from a beam in the lounge!! The water had got in through the hole and run down through several levels of breeze block until it hit a beam that was seated in the breeze block and then run along that beam. It didn't manifest itself until a few days after it had stopped raining.
See above... and then I'm very much taking heed of your point that it doesn't have to stream down the inside of a building if it's leaking. Maybe this could be running around in the roof's construction 'slowing' the flow of the water.Once again, many many thanks!
Lemming Train said:
There's an easy way to check if it's internal or external moisture penetration. When you have one of those periods when the wall clears up and becomes dry, get some rolls of aluminium foil and cover the entire area in it, taping it to the wall making it as airtight as possible. If it's an external leak then when you remove it a few days later the back side will be wet. If it's internal condensation then the front side will be wet.
Ah ha, so I read that in another thread and tried it overnight. The wall was certainly 'less damp' underneath the tinfoil but the outside of the tinfoil didn't have condensation on it. The sellotape had also come unstuck during the night... thanks to the wet wall. I will try again tonight (dehumidifier's been on all day and no one has taken a shower yet) to try and get more conclusive results.wolfracesonic said:
Do you know what's on top the chimney stack, are the flues open allowing water in? Ideally it needs cowls on it even if it's not used. It could just be water saturating the wall and showing up on the inside, it doesn't look like it's a cavity wall.
I'm not 100% sure but I believe the chimney stack is for aesthetics only and I imagine the top to be solid brick. I will confirm tomorrow.TooLateForAName said:
Have you seen the suggestion to tape some tin foil to the wall? (tape all round).
If the water is coming through the wall then the wall under the foil will be damp. If the face of the foil is wet but the plaster underneath is dry then condensation.
Is your fan any good? Does it run on or is it manually controlled?
Yep, got the tin foil on there now. Will see how it goes...If the water is coming through the wall then the wall under the foil will be damp. If the face of the foil is wet but the plaster underneath is dry then condensation.
Is your fan any good? Does it run on or is it manually controlled?
The fan is automatic and I suspect it's pretty crap. I'm going to remove it tomorrow to have a proper look.
Thanks!
Ricky146a said:
Where I live in Northumberland there are literally thousands of miners cottages of a similar design to yours. Many also have a further extension on the outshoot as yours does.
The outshoot usually has a chimney stack as your does and as your neighbour appears to have.
The stack would have been functional with a kitchen stove but probably removed internally through the 2 floors when the kitchen extension was done.
If all that is true then it is very possible (as has been suggested) that rain is getting at the top and has nowhere to go other than seep into the fabric of the house.
I think it is highly unlikely that the stack is asthetic - folk had far better things to spend their money on.
As an aside, the walls are built of limestone but appear to have been repointed with a standard portland mortar. This will only cause you problems as the years go by. I would look at raking it and repointing with a lime mortar when you can.
Yep, it's the Taylor Wimpey of the 1900's!The outshoot usually has a chimney stack as your does and as your neighbour appears to have.
The stack would have been functional with a kitchen stove but probably removed internally through the 2 floors when the kitchen extension was done.
If all that is true then it is very possible (as has been suggested) that rain is getting at the top and has nowhere to go other than seep into the fabric of the house.
I think it is highly unlikely that the stack is asthetic - folk had far better things to spend their money on.
As an aside, the walls are built of limestone but appear to have been repointed with a standard portland mortar. This will only cause you problems as the years go by. I would look at raking it and repointing with a lime mortar when you can.
And yes, totally get the logic that the chimney wasn't aesthetic. I'm wondering if the extractor fan's hole runs into the chimney flue as well as out through the side of the house...
Thank you for the tips on the mortar - this is creeping ever higher up the list of things to do here.
SAB888 said:
The chimney lead flashing looks dodgy and there's hardly any upstand. It would be worth checking it as it's right above where the damp patches are.
Yep, agreed and I'm going to see what I can do about that tomorrow - thank you for highlighting it.Lotobear said:
IMO you have penetrating damp but a range of contributory factors:
1 It's west facing
2 The ceiling is just below the stack flashing so without a lead tray through the stack water will bypass the stack flashing and appear in the room below (with a loft space the damp never reaches the habitable room). Not much you can do without rebuidling the stack to include a DPC
3 Someone has pointed the porous limestone walling with horrid cement rich strap pointing, probably in the mistaken belief that the pointing was causing the issue - rain entering the wall through the porous limestone is therefore trapped (the joints are the wall 'drains' as all construction scholars will know) and is therefore being driven inside rather than drying to the outside, aided by the joints removing the free water. Take it all out and re point with NHL mortar
4 you may also have some hygroscopic salts leached into the plaster from the old flues - this will cause the appearance of damp even in dry periods. Hack it off and replaster with a salt retardant base coat.
Once a wall is wet it is then more susceptible to condensation as it becomes cold relative to the dry parts of the wall - especially problematic in a bathroom
Fantastic points, mega appreciated.1 It's west facing
2 The ceiling is just below the stack flashing so without a lead tray through the stack water will bypass the stack flashing and appear in the room below (with a loft space the damp never reaches the habitable room). Not much you can do without rebuidling the stack to include a DPC
3 Someone has pointed the porous limestone walling with horrid cement rich strap pointing, probably in the mistaken belief that the pointing was causing the issue - rain entering the wall through the porous limestone is therefore trapped (the joints are the wall 'drains' as all construction scholars will know) and is therefore being driven inside rather than drying to the outside, aided by the joints removing the free water. Take it all out and re point with NHL mortar
4 you may also have some hygroscopic salts leached into the plaster from the old flues - this will cause the appearance of damp even in dry periods. Hack it off and replaster with a salt retardant base coat.
Once a wall is wet it is then more susceptible to condensation as it becomes cold relative to the dry parts of the wall - especially problematic in a bathroom
Okay so a lead tray would seal up the chimney, right? So if I go up there and see that it needs sealing I could temporarily bodge something together to put a cover over the top, hopefully reducing water ingress. Or does the tray sit at the base of the chimney stack?
And yes, the pointing isn't great. Luckily the rest of the house is 'fine' but your analysis seems to make sense - they've maybe tried to fix this issue before with misguided efforts. Looks like we need to get this addressed ASAP (as above Ricky146a pointed out).
Thanks for the plaster recommendation too. I'm going to google that and work it out - cheers for the lead!
TooLateForAName said:
Just wanted to say, be really careful if looking at the stack. It isn't unusual to find that the mortar is rubbish and its basically just sitting there waiting toi fall down Esp around the corbells.
Thank you! Noted and extra caution will be taken tomorrow!Is this general builder territory or do you think that certain trades specialists are better sought out?
Once again, thanks to all who have commented so far, the help is really appreciated.
Once again, thank all for your replies.
So an update:
- I went up there on Saturday to see what was what. There were quite a few gaps and cracks in the pointing and stone work so (maybe wrongly, please advise?) I siliconed up what I classed as a larger gaps. I guess the problem with this is that the holes I've filled could be ingress holes for water rather than egress holes. But, my logic for filling them was to rule out the pointing needing redoing.
- There were also some gaps between the top of the roof and the chimney flashing so I filled those best I could with silicone. Hopefully this'll rule out the roof being at fault or the lead flashing around the base of the chimney.
- I also removed the grey mushroom that was the exhaust for the extractor fan. Turns out that very little air could get out. On the positive side, the extractor has a solid 100mm pipe through the wall so there shouldn't be any damp coming from that. Negatively, it doesn't run down towards the outside. Anyway, I replaced the mushroom with a gravity flap cowl. This'll hopefully go some way to reduce the amount of moisture in the room during shower time.
- I couldn't get my hands on a suitable ladder to look at the top of the chimney but I should have one this week so will go up there and inspect. I'll throw a tarp over it and attach that to the chimney. Hopefully this'll eliminate the chimney being the source of water ingress.
Once I've got to the bottom of that I'll know how to proceed with getting a builder in...
Thanks all!
So an update:
- I went up there on Saturday to see what was what. There were quite a few gaps and cracks in the pointing and stone work so (maybe wrongly, please advise?) I siliconed up what I classed as a larger gaps. I guess the problem with this is that the holes I've filled could be ingress holes for water rather than egress holes. But, my logic for filling them was to rule out the pointing needing redoing.
- There were also some gaps between the top of the roof and the chimney flashing so I filled those best I could with silicone. Hopefully this'll rule out the roof being at fault or the lead flashing around the base of the chimney.
- I also removed the grey mushroom that was the exhaust for the extractor fan. Turns out that very little air could get out. On the positive side, the extractor has a solid 100mm pipe through the wall so there shouldn't be any damp coming from that. Negatively, it doesn't run down towards the outside. Anyway, I replaced the mushroom with a gravity flap cowl. This'll hopefully go some way to reduce the amount of moisture in the room during shower time.
- I couldn't get my hands on a suitable ladder to look at the top of the chimney but I should have one this week so will go up there and inspect. I'll throw a tarp over it and attach that to the chimney. Hopefully this'll eliminate the chimney being the source of water ingress.
Once I've got to the bottom of that I'll know how to proceed with getting a builder in...
Thanks all!
Wayne E Edge said:
Your chimney flashing might be fine but still won't stop damp passing by without a DPC.
I've been a roofer for 40 years and the amount of times I've heard....."I have water leaking around the chimney, must be a flashing issue" is unbelievable.
Someone said earlier in this thread about lofts used to be lofts and you wouldn't notice. As soon as you make a liveable area there it comes to one's attention. Well, he's bang on. Another thing with old chimneys is they were expected to have heat put through them from the fire. That is why they never bothered with a DPC.
If I don't get a dozen calls this month about this same issue I'd be surprised.
I see - so where does the DPC go on the chimney? Would putting a tarp over the top of it help temporarily?I've been a roofer for 40 years and the amount of times I've heard....."I have water leaking around the chimney, must be a flashing issue" is unbelievable.
Someone said earlier in this thread about lofts used to be lofts and you wouldn't notice. As soon as you make a liveable area there it comes to one's attention. Well, he's bang on. Another thing with old chimneys is they were expected to have heat put through them from the fire. That is why they never bothered with a DPC.
If I don't get a dozen calls this month about this same issue I'd be surprised.
Many thanks.
Lotobear said:
The dpc needs to be built into the chimney at the time of construction - it is formed in lead sheet and is introduced to coincide with and lap over the external cover flashing and then also has an upturn within the flue. It's a complete barrier running through the entire structure of the stack masonry
Your only other option is a good render system without taking down the stack and rebuidling with a dpc tray but that's a compromise.
You could take the stack down and roof over but you lose something aesthetically with that approach especially on an old building (IMO)
Ah ha, yes, sorry, I thought there was an additional DPC beyond the lead trey that another member described. I think in this instance (if the chimney is leaking - and it sounds like it almost certainly is) finding a solution that doesn't involve taking the thing down is preferable. I'll get that tarpaulin to start and go from there...Your only other option is a good render system without taking down the stack and rebuidling with a dpc tray but that's a compromise.
You could take the stack down and roof over but you lose something aesthetically with that approach especially on an old building (IMO)
Cheers!
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