What’s causing this damp?!

[Holls81]

We have a real head scratcher.

There’s a small patch of paint that peels off in the top corner of our chimney breast. (Original patch was a couple of cm.)
(downstairs in the lounge.)

I sanded the paint round the area right back to where it stops flaking off.

The plaster underneath looks darker and the metal beading down the edge is rusty in a small patch.

Now, we asked a roofer to check the flashing and he said that if it was a problem with the flashing then the problem would also be evident upstairs (which it doesn’t seem to be.)
Structural engineer came out for something else and while he was here I asked his opinion. He too had no idea other than that it could possible be a flashing issue.

We’ve had a lot of rain over the past couple of weeks and the patch doesn’t seem to have changed (ie looking wetter or drier.)

when I sanded the area, down the side in a small gap in between the cupboard and the side of the chimney breast, some wall paper came off which seemed a little damp but not mouldy. (This is not a cavity wall)

Is it possible that condensation could be causing it where the air can’t get in to the little gap and the wet wall paper, that has seemingly always been in there (we’ve lived here 10 years and haven’t ever had wallpaper) might have been holding the water and not allowing the plaster around it to dry?

I’ve heard @pigletjohn might be able
to shed some light?!

not sure what else to try!

*I should also add that the dark patch on the plaster is my greasy finger print from the other day 😫

Damp readers shouldn't be used on on houses.

There are lots of cowboys out there- it's a big industry.

Suggest you do some of your own reading around the subject.

Is the house brick or stone?

@Holls81 My place is similar age to yours 1860. My patch was just like yours. I’ve got a wood burner too that was put in by the previous owners with a lined flue that I had checked out and it’s not what’s causing the problem. Once I’d done the salt neutraliser I used Zinsser Gardz and then Zinsser Bulleye 123 and have painted over and nothing shows through - for now!
I was advised to paint the whole of the chimney breast with the 123 as it gives a more even look when you repaint.

We didn’t have that. Do you mean that something else should have been done to the walls on the outside to stop the water coming in?
It’s all so confusing!

@SquishyGloopyBum
its brick

Wet at the foot of walls might be a result of ground or paving sloping towards house to bring rain puddling against the walls. Dripping gutters and blocked downpipes also. Or it can be broken drains (very common) or leaking pipes, but this is worst close to the leak.

Your house might not have a DPC, but does it have a wooden ground floor with a ventilated void beneath?

Damp can pass up brickwork quite a short distance, until it reaches the point where evaporation from the surface equals water passing from below. Renders, paint, and especially cement plinths (often done to hide damp but actually make it worse) prevent evaporation so make the wall wetter.

Older houses often have the ground against the house raised with paving, or even flowerbeds, adding damp and reducing evaporation.

@Karmatime thank you. Your post has made me feel a little better. 🙂

@PigletJohn thanks for this. You’re so knowledgeable! What is your trade?! Do you live near me?! 😂

This actually makes a lot of sense. When the preservation company came, they said that the ground around the house was too high and not letting the bottom of the house breath.(there was a row of shingle around the house) We were having the drive way done the following month and the guy who did the drive also said that the ground was too high so lowered it by 8 inches. He put shingle around the house to let it breath.

The ground floor is quarry tile throughout. It’s been like that since 1998 (I know the people who put it in)

Chimney breasts often have the bricks and plaster sort of infused with smoke from historic use and this can cause damp to be sucked in from the air.

We have had this in our 1870 terrace and our 1820 house. It might mean regular repainting if you can’t be bothered to have the plaster hacked off. Personally I can’t!

If that's your chimney wall you've got water coming down your chimney making the damp. If it was anywhere else then it's more than the chimney but from your pics that's looks similar to what we had in last house, ended up almost having whole chimney redone and after a few days the wall dried up and we decorated

@Parlourgames this made me laugh 😂
I can’t be bothered either but part of me just wants to know what it is 😂
I think I may need to come to terms with the fact that we may not know and I think a lot of things like this happen in houses and people just don’t know why!!
did someone tell you that that’s what was wrong with yours? Or did you just come to that conclusion once everything else was ruled out?
I’d he more than happy to just keep painting over it but if there’s something underlying then it’s niggling me!

@Ladyj84
wow! That’s really interesting. When you say you ‘had almost the whole chimney redone’ what do you mean?

I had this. A surveyor confirmed it by taking a sample from the chimney breast. I avoid it now by not drying clothes in that room and ventilating it more. I painted a stain block over the affected area and then painted over.

It’s a known thing with old chimneys old houses … hydroscopic salts in the plaster.

ours is quite wild - the shapes and patterns change according to the dampness in the air.

Sorry it’s called Hygroscopic salt - do a Google with those words and “chimney plaster”

We had staining on our chimney breast too, which became apparent when we stripped off the wallpaper and replastered. I don't know for sure that it was hygroscopic salts but we painted with Zinsser BIN and repainted and had no further issues. That was about 15 years ago and had no further issues.

If you have an old cottage with solid walls that you have tanked you need to find a surveyor who knows old buildings. They don't have a dpc - the walls are designed to breathe. Tanking might have forced the water further up the walls.

Have a look at https://www.spab.org.uk/sites/default/files/SPAB%20Technical%20advice%20note-Control%20of%20Dampness.pdf

If you are on facebook join this group for very expert advice. I speak as someone who wasted thousands on an injected dpc with new gypsum plaster https://www.facebook.com/groups/1023449561785486 Now I'm pulling off concrete and repointing in lime and the next project is trying to get the modern plastic paint off lime plaster on the external walls.

@CurrentlyChipped oh gosh, that sounds terrible! How come you feel you wasted the £1000s? Have all the problems come back?

so the preservation company suggested we lower the ground outside the house, (the shingle and level was too high for the house) which we did.
The wall that we had damp proofed (I believe it was with some kind of slurry) where the ground was too high, was wet through. The plaster was falling off and was actually damp to the touch and smelled musty.

@CurrentlyChipped just scan read that info. I’ll have a proper
read later with a cuppa. Looks really interesting.
thank you!

My problems never went away! Personal circumstances meant I wasn't in a position to chase it up. If only there were some precedent for suing cowboys with the wrong approach to historic homes. I have a capped chimney with what looks like all the chimney remnants inside the flue so no ventilation. I now have a kitchen and another room with bare plaster that never dried properly that I'm longing to get sorted. The damp units have been replaced by a beautiful vintage french dresser that I have just discovered is getting musty. Upstairs the big damp patches on the chimney breast are still there. I am still waiting to organise the historic buildings surveyor.

Your walls MIGHT have been better off being left to dry after the exterior ground level was lowered. Then replastered in nice breathable lime. But I'm no expert - I've just been picking bits up now I know where to look and whose advice is better listened to,

Check out the Heritage House website, there is a lot of info there.
I'd be wary of ding any more tanking unless the level of the wall is below a ground level that can't be lowered instead, and even then I'd take advice from the likes of HH or an expert surveyor of old houses ( not anyone who sells damp-proofing of any sort).

Thank you. I definitely will check it out. We have no plans to get anything else damp proofed! We only did so previously because it seemed the obvious tradesperson to call on… you have damp walls, who you gonna call?! (In theory anyway!)
Lots of problems here have been solved by using dehumidifier when drying washing and extractor fan while cooking alone.

I’m now curious as to what the rest of the house is plastered in 🤷‍♀️

This sounds horrendous! You poor thing.
i agree. So many cowboys and what I find so annoying is that everyone seems to tell you differently! I struggle a lot with anxiety and the fact that I can’t seem to get any definitive advice or answers, really gets me down.
I’m going to sit down and have a good read tonight.
I hope you manage to get your house sorted.
Are toy doing a lot of it yourself?

I get salts in a corner in my bedroom. I'll post a pic when they next return...

Could these residues alone, cause salts, or would there also have to be another reason?

so clueless- sorry! 😂

Using a dehumidifier in the smallest bedroom to dry clothes, extractor fan and lids on saucepans in the kitchen seems to be helping a lot for us. We’ve yet to have a winter here but have a brand new boiler so hoping it will be ok. Any advice on best heating schedules to avoid condensation build up? Sorry to derail!