Problem damp corner in front room - condensation?

Question

About ten years ago I had some plastering work done with sand / cement / additive plaster about 1m high across the front of the room, and the rest of the room just skimmed over. There is a persistant damp area above the line of the new plaster going up to ceiling height and appearing to a lesser extent in the hallway by the front door on the other side of the wall. Paint has 'bubbled' and some of the plaster skim has blown away from the wall.

One of the walls affected is cavity which has been filled with loose insulation, but the other can only be half a brick thick as it is the internal hall / front room wall extending past the front door where there is an open porch about 1m deep.

I am fairly sure that the damp is condensation but no other part of the room is affected. There is a radiator under a bay window to the right of this corner but being in a bay might leave the affected walls cold. I have installed trickle vents over the double-glazed wooden sash windows and the room doesn't 'feel' damp.

If necessary I can get at the cavity wall by removing the timber which closes the cavity where it turns into the bay, and drag out the insulation and check for water ingress, although obviously I'd rather not! Shoul I re-plaster, or is there something I can treat the plaster with? Should I insulate the half-brick wall outside the front door, and if so how?

Any advice gratefully received

Peter

Phil L · Accepted Answer

This sounds supiciously like the CWI has not been installed properly.

1) How long ago were the walls insulated? 2) do you still have the guarantee? - it's probably got the word 'CIGA' on it 3) Was the problem there prior to inulation works taking place? 4) is your hous cavity wall from DPC to roof or is it clad at the bottom or top?

Stuart Noble · Answer

Not much help but.....penetrating damp is most common on south/south west facing walls. If your half brick wall points that way, I'd say that was the problem.that much condensation would be unusual if the radiator was functioning normally. If you get damp there in the summer, it's almost certainly not condensation.

George (dicegeorge) · Answer

Re: Problem damp corner in front room - condensation?

What im thinking of doing is marking a few points A B C D... on some damp places and every day taking readings with a damp meter gizmo and writing them down with the day's weather then a month later make a graph then somehow figuring out if it's rain or condensation..

(However I know its because of the gaps between some slates)

Problem damp corner in front room - condensation?

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