Strange damp patches on walls

marymac27

Hello hello, 

I wondered if anyone can help me….I’m at a bit of a loss. I had my bedroom walls skimmed a few months ago and they are yet to be painted. Every morning these damp patches appear on the back wall and window wall. They go if the windows are opened or dehumidifier on so guessing it’s condensation but what I’m wondering is does anyone have any advise on how to fix this before painting? They are external Walls but I can’t see any sources of damp. Any help would be hugely appreciated!!! I have included some pics. I’m just hoping I don’t need to take the plaster off and start again 😬. 

Thanks, Fiona x 

Jonathan_Powell

Have you asked the prison warden to take a look? 

koalakoala

You need to get something on the walls !

marymac27

Thank you for the decorating tips but actually I was asking about how to sort out the damp before I paint the walls. 

This is plaster that hasn’t been painted yet because of this problem….not just an aesthetic choice! 

Bendy_House

marymac27 said:

Hello hello, 

I wondered if anyone can help me….I’m at a bit of a loss. I had my bedroom walls skimmed a few months ago and they are yet to be painted. Every morning these damp patches appear on the back wall and window wall. They go if the windows are opened or dehumidifier on so guessing it’s condensation but what I’m wondering is does anyone have any advise on how to fix this before painting? They are external Walls but I can’t see any sources of damp. Any help would be hugely appreciated!!! I have included some pics. I’m just hoping I don’t need to take the plaster off and start again 😬. 

Thanks, Fiona x 

It doesn't look like condensation, Fiona; it's too localised and well-formed in the places where it appears. Yes, it might clear when you ventilate the room or use a dehumidifier, but that's just because it temporarily removes the moisture that shouldn't really be there in the first place.

Because it's so localised and well-defined, I have to say my suspicions fall on it being 'penetrating' - ie coming through from outside. Are these external walls? Are they solid walls, ie no cavity? Has it been raining a lot? Could you post some photos of whatever is on the other side of these walls, please?

Porridge for tea again?

FreeBear

Can you move the bed so that the headboard is up against another wall ?

I'm suspecting that the damp patches are a result of heavy breathing during the night - Being fresh plaster, the problem may well look a lot worse than it actually is.

Norman_Castle

marymac27 said:

 Every morning these damp patches appear on the back wall and window wall.

Before plastering was the wall papered? Do the patches appear regardless of overnight rain?

Was the wall skimmed or were areas cut back to the brickwork? Deeper areas of plaster will take longer to dry out and will dry on the surface when well ventilated then wick water from deeper in the plaster. Presumably you close the window and door when sleeping in the room.

marymac27

Thanks all for you comments. I did have porridge this morning thanks 😅. 

So beneath this new skim coat was some
paper that would not come off….it was really welded on. The plasterer had to seal and skim over. It was just a skim coat onto the old plaster so not too thick. This was done in March though so I’m guessing it’s dry. 

The walls the damp is on are all external, sandstone and render on the other-side. 

Do you think it would be a very bad idea to go ahead and paint? I’m thinking the paint would bubble….

thanks again for the advice! 

marymac27

Also….rain seemed to make no difference to the patches….it’s more just sleeping overnight that causes them..:

Grenage

What's the state of the render on the outside?

marymac27

Render is fine. Can’t see any cracks. There’s render on the back wall and the side wall is the original sand stone, in very good condition. 

I was wondering if it was sealing the paper that’s caused moisture to get trapped beneath the skim coat….?