We have a typical three bed 1930s semi with the “box” room at the front of the house on the external side.
This previously had built in units on the external wall. The PO had installed these. There was a cable channel not hidden in the wall which came out from behind the unit, up the channel through the coving to the loft with a live & earth. In the top centre of the wall was a vent and an air brick on the opposite side externally.
We have no use for the built in units so have removed them, there was a little damp on the external wall behind the units, I suspected cold air from the floor meeting warm air in the room and condensing on the paint.
About 50% of the plaster was blown, it was old stuff with a skim on a skim...
I’ve stripped it right back to brick, removed the coving and gone up to the ceiling.
I plan to reboard using 12.5mm plasterboard. I should be able to do a small board say 300mm high at skirting level, then get two 1.2*2.4 side by side and only have three joints to tape/skim. I’ve done some plaster boarding before and the results were pretty good. Massive lead in time for a professional at the moment, so for the £30 of materials I’ll try it DIY first.
I was wondering if I can just brick up the air brick space? This had a poorly done wooden boxing job in there which had been plastered over/up to and a piece of polystyrene wedged in there to cut down on the heat loss.
There are no fires or chimneys in the house anymore, it’s all gas central heating. There’s a window which opens if needed. All the air brick does is mean that all the heat in the house goes up the stairs and disappears out of it!
https://imgur.com/gallery/dHOD6Ff
Damp will be about a lack of airflow behind the units. I don't think you will need to cover the air brick, and isn't it meant to be needed for the building to "breathe"
What type of windows do you have in that room?
Do they have trickle vents fitted?
It's not advised to block up airbricks (however most people do) you need good ventilation through the property to alleviate condensation and damp/mould growth.
It’s a fairly normal double glazed unit, no trickle vents.
None of the other bedrooms (larger) have air bricks or vents, just the bathroom. No internal air vents downstairs either that I am aware of (unless they have been plastered over).
Yes I think the damp behind the units is lack of air, have found that all the external walls need airflow around them, even just a few inches is enough.
If you brick up the air vent where it passes through the inner leaf of the wall but leave the air brick in the outer leaf you may create a cold spot which could attract condensation on the face of your plasterboard drylining. Not likely to be a major issue really. Have you thought about some thermal insulation behind the plasterboard? It should help keep a potentially cold room a bit warmer.