Help with my damp spot, please

[BackPedal]

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]

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?

[BackPedal]

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.

As for the dampest spot, it's right in the corner of the wall, not on the ceiling... I think!

Thanks!

[Ricky146a]

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?

[wilksy61]

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.

[Lemming Train]

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.

[WyrleyD]

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.

[BackPedal]

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.

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.

Thanks again!

Edited by BackPedal on Friday 9th November 18:33

[BackPedal]

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!

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]

BackPedal said:

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.

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.

Thanks again!

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.

[wolfracesonic]

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.

[BackPedal]

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]

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?

[BackPedal]

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...

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]

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.

[SAB888]

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.

[Lotobear]

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

[TooLateForAName]

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.

[BackPedal]

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!

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.

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.

[Ricky146a]

BackPedal said:

Is this general builder territory or do you think that certain trades specialists are better sought out?

If it is stack, pointing, tiling, flashing, plastering ......
This would probably involve a few trades but a decent general builder will know the right experts in the area to call in - probably cheaper than you can get.
Just choose your builder carefully and get at least 3 opinion/quotes.
Good luck.
These are exactly the same problems I come up against in my renovations.