Where to start? Tackling damp bedroom's cold walls

[_bitbybit_]

Hi,

I feel helpless to resolve a major condensation problem in our bedroom. I just don't know who to ask for help: a builder, a plasterer, something else? I've already had two different damp specialists take a look and they simply tell me what I already know: that it's condensation not damp. They do not recommend any course of action except to consider paying for a PIV airflow system, which is unfortunately not suitable for a flat. (Who wants their flat turned into an industrial ventilation factory with exposed air ducts running from room to room to a central air-con machine?)

The room is north facing, in an elevated ground floor flat, in a place with lots of rainfall (Glasgow). I've tried all the usual recommended solutions to the problem - reinstalled the air vent, moved furniture away from the worst affected walls to improve circulation of air and heat, running a dehumidifier, opening the window during the day, sleeping with the door open. The problem still persists, although it's not as extreme now thanks largely to sleeping with the door open.

What I think needs to be done next:

- Get someone to inspect the air vent to see if the hole sizes and the external air brick dimensions would accommodate the Envirovent kit, which would be better at drawing out warm air than the open hole currently in the wall.

- Get someone to inspect the plaster in the corner of the room to see if it needs scraping back and redoing. It could be that the previous owner's tradesmen didn't let the plaster dry out properly before they redecorated it. When we bought it, it had been completely redecorated. (I'm guessing it was they who blocked up the air vent.) When I tap on the walls in that corner, and on the spots where the condensation is worst, it sounds hollow, like it's not the original brick but is plasterboard. Maybe there's some poor quality workmanship behind the problem?

Does anyone here have any experience with this kind of problem and do you think my concern about the plaster is realistic or just paranoia?

Thanks! Photos attached for help visualising the issue.

 

[He who knows]

If two specialists have ruled out penetrating damp then it must be condensation. I wonder why the walls are so cold - are they cavity, or solid? "Elevated GF flat" - what's below - another half-basement flat? I wonder if they have any problems in the same place?

Sounds like you're doing the right things, and restoring the vent to improve ventilation is good, but at the end of the day all the air you remove from the flat has to be replaced by fresh, damp, Glaswegian stuff from outside....

The hollow sound might be blown plaster, or, as you say, plasterboard, probably dot & dab. It might be an idea to take it back to brick,

a) to check if the actual wall is damp

b) to minimise the loss of space to what might be the best solution which is to insulate the wall internally.

 

[_bitbybit_]

Thanks for your reply. I've answered some of your questions:

"I wonder why the walls are so cold - are they cavity, or solid?"

Cavity walls. c1932 construction. The front external walls are red brick covered partially with sandstone facing, up to window height, thereafter pebble dash up to the top floor flat. I've checked for loose mortar and obvious signs of cracks or damage but not seen anything. (Although that doesn't mean there isn't something wrong there. Would a builder help me with that? Or do I need a stonemason?)

"Elevated GF flat" - what's below - another half-basement flat? I wonder if they have any problems in the same place?"

Just a crawl space. Our block is partway down a hill. The ground at the back is slightly below the floor level of the flat but is a substantial 5 feet or as much as 5.5 feet below our bedroom floor at the front. One thing I'm concerned about is whether we need to take up the floor to inspect stuff. It's so disruptive. Would we need to get a builder round to look at doing that, as well as the above? Or some other trade type?

The neighbours in the ground floor flat on the other side of the building are tenants, who've only been there a short time, and their landlady is absentee and not very easy to get in touch with. I'm not sure she would be forthcoming about damp problems.

"the air you remove from the flat has to be replaced by fresh, damp, Glaswegian stuff from outside"

Ha! Indeed. I came across Perma-vent by Envirovent when I was searching for answers previously. The Perma-vent is a plastic tube connecting an external air brick through the cavity space to the internal air brick. The stated claim is that this naturally pulls out warm moist air and will push in dry air. I am more or less decided on getting this done to improve the ventilation, at least. (It won't make the room warmer...)

"The hollow sound might be blown plaster, or, as you say, plasterboard, probably dot & dab. It might be an idea to take it back to brick,

a) to check if the actual wall is damp

b) to minimise the loss of space to what might be the best solution which is to insulate the wall internally."

What sort of tradesperson would be able to advise me on that? It sounds like something that would definitely reveal the required course of action to sort the room out.

 

[He who knows]

One thing I'm concerned about is whether we need to take up the floor to inspect stuff. It's so disruptive. Would we need to get a builder round to look at doing that, as well as the above? Or some other trade type?

Lifting floor boards is a DIY-able job

The neighbours in the ground floor flat on the other side of the building are tenants, who've only been there a short time, and their landlady is absentee and not very easy to get in touch with. I'm not sure she would be forthcoming about damp problems.

I was wondering about the possibility of a flat below yours.

What sort of tradesperson would be able to advise me on that? It sounds like something that would definitely reveal the required course of action to sort the room out.

Removing plaster and/or plasterboard is DIY-able. As is insulating internally. You might need a plasterer at the end to skim new boards, but you can get a pretty good result with careful filling of nail/screw holes and taped joints followed by extra-heavy lining paper, then painting.

 

[_bitbybit_]

Apologies for my much delayed reply. Thanks for considering my questions and sharing some ideas for solutions.

 

[Daxbuddy]

Just a thought... If the previously blocked air vent is carrying moist air through a cold wall, perhaps it is the delivery mechanism of the condensation? With that vent closed off, was there any less condensation apparent?

 

[_bitbybit_]

The air vent has greatly helped things, though: it’s massively reduced the size and degree of the condensation in that corner.
But at the same time as improving ventilation it is making the long wall it blows air onto colder than it was before. On a hot sunny day recently I noticed for the first time a few small sprays of mildew spotting along the upper part of that wall. I cleaned the entire wall by hand with a detergent solution and bleach, then dried it by hand with an old towel, and left the window open all day to finish the drying. So I have to insulate the wall, I think.

 

[_bitbybit_]

Thought I’d share an update to this problem. I paid a heritage surveyor to inspect the wet bedroom walls. He discovered from taking thermal imaging studies of the external walls and adjoining rooms that the wall surfaces where the wetness occurs are several degrees cooler than the rest of the wall. After investigating the crawl space, he could confirm definitively that there is no water ingress causing the wetness. He also examined the pointing outside the bedroom and the window frame too. No issues there.

He recommended internally insulating the two external-facing walls with thermal paper. Until he told us that, I didn’t know that such paper even existed. After researching it, I’ve found that Wallrock thermal paper gets great reviews and it’s only £55 a roll.
We’re installing the Wallrock paper next weekend and I am very excited about it!
Hope this info helps others.