This is the archway linking the two halves of my basement - I believe it is in a load bearing wall.

I have a dehumidifier in the basement which has cured all previous smells of damp, and there are two radiators providing heat down there.

The powder is dry to touch, and when you wipe this powder away it returns within a couple of weeks and gets thicker the longer you leave it!

The basement was damp proofed by the previous owner, but I think it was a pretty cheap job - just a layer of polythene sheet behind the plaster board.

What is the white powder?

How do you get rid of it?

Thanks in advance for any advice!

TIMBA-WOLF wrote on Mar 28^th, 2013, 4:21pm:


2nded.  looks exactly like what was on our bathroom wall when the roof was leaking

you'll need to find where the water is coming from before you can work out how to stop it.  i'd start with a thorough check directly above it for any leaking pipes.  a cheapy damp meter (search ebay for 120645124866 ) tha i use for checking firewood before burning it helped me trace the damp in out bathroom.  even though we were only getting a fluffy wall in one small area, i could trace the damp patch (you couldn't see it or feel it by hand) up the wall, then up the sloping ceiling. only down side its that it does leave 2 little holes in the surface