Solid stone building excessive damp

[NameChange564738]

Just wondering if anyone has even the faintest idea as to what the hell is causing our damp?!

Solid stone structure built in 1901 ish.
Gable (pine) end wall is excessively damp BUT the attic is bone dry.
Cement render has been hacked off and replaced with lime (this has actually appeared to make it worse).

It rains and a few hours later the whole wall is wet.. end of my tether now and getting understandably down about the whole situation.

I’ve read something today regarding salts in the chimney(?), they are concreted up at the actual fire places (4 in total on gable end wall, one in each room) and chimney has been removed above roof level so it’s just a hole in the wall in the attic.

Anyone dealt with this? Or know someone who has?

[UnconsideredTrifles]

We are in the process of buying an old stone house with damp (DH is a builder so not as mad as it sounds!) Similarly dry attic, and recent render so we know it's not coming through the walls.

I think he's concluded that there's no damp proofing under the floor. The plan is to dig drainage around the house (land around it is higher) and, if that fails, dig up the floors and lay a membrane.

[PigletJohn]

wet wall all the way up? Could be rain cascading off the roof or guttter.

Damp from the ground may travel up several feet in a random rubble wall, depending on absorbency of stone and building method. but will not rise all the way up a house.

Render can make it worse. Render is usually applied to walls to hide some defect or poor condition.

I am in an exposed coastal location and one wall is slate-hung, which sheds storm water like a waterfall.

[CharlieTangoBanana]

The fireplaces being bricked up could be the problem, old buildings need to breathe, it's good that you've replaced the plaster with lime and it could appear worse because it's drying out. If it gets noticeably worse after rain it's probably sleeping through the outside wall so it sounds as if it needs repointing.

[PigletJohn]

but if it was chimney damp, you'd see the pattern of the flues showing through, it's pretty unmistakeable.

[NameChange564738]

There’s no damp proofing under the floor

I was under the impression that damp proofing is for building built with modern materials that don’t need to breathe? I’ve been looking at the heritage house website and their equivalent YouTube channel (doesn’t make me a builder I know!! ) But I’d be very interested to hear any possible solutions.

@PigletJohn
its quite complicated but I’ll try and explain succinctly:

We’ve removed outside render, redone any faulty pointing and rerendered in lime.

Inside: 4 rooms..
Upstairs room 1 has had gypsum plaster and black mortar taken off back to stone/brick. My hang work one bored Saturday afternoon so not a great job. Fireplace is concreted up. Was incredibly wet when I removed it and has subsequently dried and not become wet again since.

Upstairs room 2.. still has black mortar and gypsum plaster on the stonework along with concreted up fireplace. Very wet, it seems to follow the line of the two chimneys through the wall (one from downstairs travels partially through the wall too). Gets worse when it rains.

Downstairs rooms are pretty much knocked through but each side is very different so will call them room 3 and 4: room 3 and inch thick foamy type plaster board on top of black mortar, bone dry regardless of weather. Assuming chimney also concreted but haven’t made a hole.

Room 4 same inch thick foamy plaster board on black mortar, where this touched the wall it’s sopping when it rains, almost immediTely. Well within a few hours. Then it dries out as soon as rain stops. This also follows the line of the chimney mainly. I have seen online images of ‘cold spots’ which looks almost identical.

Attic/roof/guttering checked and it’s all bone dry even in super wet weather. I should mention the chimney doesn’t break through the roof it’s been removed.

[NameChange564738]

@CharlieTangoBanana Would a vent brick be sufficient of must it be removed completely.

[PigletJohn]

chimneys need to be ventilated top and bottom so air can rise up them and evaporate away water vapour

When you open them, remove the piles of rubble that past builders probably hid inside. If you are sure the chimney will never be used again, it can be helpful to break up the hearth and dig out the rubble fill below floor level so the walls can have a chance to evaporate off. When there is a wooden floor with a cavity you can sometimes remove a brick or two so that air from the floor void can escape up the chimney.

A local chimney sweep should be familiar with local materials and techniques and be able to advise. Remove soot from the flue because any damp will cause tarry brown stain to penetrate through the plaster.

I think the impervious boarding you mention is probably trapping moisture and preventing it escaping.

[chloworm]

Yeah it'll be the chimneys. Concrete is the enemy in old houses. It's normal for old walls to be a bit damp as the house needs to breathe. Remove all concrete and rubble. Replace with limecrete if needs be. But better to not block fireplaces at all.

[chloworm]

Damp proof course is not recommended for old houses and can cause damage to structure. Ventilation and breathing is the key.

[gonewiththerain]

Lime plaster on the inside as well with lime wash so the whole wall is breathable. Concrete and gypsum plaster really attract and hold onto water so get rid on those materials and the problem should go

[NameChange564738]

@PigletJohn that all sounds doable, I wouldn’t be surprised if it’s full of rubble the cement job is shite. It’s run half way across the wall at the bottom. Thank you for taking the time to read and respond.

How does the water get in there though? Is it moisture in the air? That has been my only last thought. Windows are old and you can feel a draft through them so ventilation is accidentally great in this house.

I agree - boarding was put in when the house was ‘renovated’ before we bought it. That will probably come off too.

Next step: Going to get a quote for repointing inside and removing cement from fireplaces, I quite like the higgly piggly stonework.

[PigletJohn]

a sealed chimney gets condensation inside from the air in the house. I think they call it water vapour pressure. Anyway, opening top and bottom will get the air flowing through. Water vapour is lighter than air (hence clouds) so will naturally rise out of the top if it is allowed.

When winter comes, if the draught is severe, you can reduce the gap at the bottom to an airbrick size, but no smaller. For appearance, you can put grilles at the side rather than the front.

[Didicat]

Depending where you are you could get a conservation builder consultation who will tell you what needs to be done to remedy the problem, what materials to use and the cost.

Know of a good one in Wiltshire.

[CatherinedeBourgh]

Not traditional, but mechanical ventilation can really help with damp in old houses.

[Kilbranan]

OP
Not directly relevant to what you were asking but is the foamy board you mention like internal insulation on walls? We’ve seen a house with this and weren’t sure how bad this might be in terms of damage /damp behind the boards. Have you taken any off to assess how it is behind it?
Lots of good advice on this thread, hope you get things sorted