I have a first floor flat built in 1985 which I bought for my son .
It is at the end of a block and the bedroom and living room have one wall .which is an external wall as it is at then end of the building
The flat was built by Wimpey and the walls are cavity concrete block roughcast,
When I bought it in 2003 the surveyor told the previous owner to repair a broken rainwater downpipe which runs down the corner of the bedroom external wall ,which they did.
The previous owner had no heating in the flat and said to me they did not like the heat.
Anyway, I put in electric storage heaters and new double glazing in 2008.I also had the roof guttering cleared of leaves occasionally.
I notice that black marks are appearing in the corner or the bedroom where the original leak from the down water pipe may have caused water to run down the external wall.
There is no window in the bathroom so I installed an extractor fan.
My son has his bed against what is the external wall in the bedroom and a little set of drawers in the corner of the room where the damp/mould is evident.
I have asked him to move his bed and drawers to the other wall which is an internal wall ,hoping this might help.
I am not sure what to do as we have tried mould remover on the wall but the damp or mould has come back.
Anybody got any ideas?
