On 17/12/2020 22:12:48, Monique Castellani-Kraan wrote:
Hi all, could use some input on this because I'm a bit of a novice
and need to make sure I'm using the right tools for the job!
Our house was built in the 1940s and we've lived there for almost 30
years, and little did we know there was a badly filled-in air brick
inside my build-in clothes wardrobe. In recent years I wondered why I
had such a bad clothes moth problem and why my clothes smelled
fusty.
The air brick is 6 ft above the floorboards, directly inside my
enclosed wardrobe. It is in a contained space consisting of only my
clothes wardrobe and bookcase inside my bedroom. Photos here.
https://imgur.com/a/KCKaehO
It seems the previous people did a bodge job and filled it in from
the inside using only plaster filler, so of course over the years the
plaster has deteriorated and crumbled - and has now had an explosion
of mould growth that spread all over the walls and ceiling in the
upper storage section of my wardrobe. Had to absolutely blitz it with
bleach and throw a load of stuff away. (and for anyone wondering how
I didn't notice for so long - I use the upper level for storage so I
couldn't see what was happening until it was too late)
So needless to say this air brick needs filling in because of its
ridiculous location. Now the question is what do I use to seal this
flipping thing up for good so that this doesn't happen again?
It would have to be sealed from the inside as this is an upstairs
room. Would it be feasible to scape off all the old stuff, seal it up
with repair cement, then re-plaster and paint? Any help and tips
would be greatly appreciated. Brands and recommended products
especially. Thanks! 
Clearly one or more of those walls is an outside wall. It is therefore
going to be colder than the room so condensation will form on these walls.
Given the passage of time, apart from the refilling of the airbrick, you
need ventilation between the room and wardrobe. I would suggest a series
of holes in the bottom and top of the wardrobe between that and the bedroom.