What to do about wall stain

Leif

I had an old boiler removed from my kitchen and the hole into the flue was filled with a breeze block and plastered over. Recently damp appeared on the wall where the hole was, and there is now a stain. This was when there was continuous rain and wind. The flue has a cowl, with small side vents, and clearly damp got in. The breeze block must be very absorbent. Anyway, is there anything that can be done? If I just paint over the patch, the problem will reoccur if we have another 4 weeks of continuous rain and wind. Or is there a sealer which can at least reduce or prevent staining?

The worst case is to hang a clock over the stained area.

iamcornholio

You need to coat it with a stain block first

System

if its going to be a reoccurring problem could you not see if its possible to change the outside cowl vent .

Leif

CHRISSYG wrote: »

if its going to be a reoccurring problem could you not see if its possible to change the outside cowl vent .

I will go on the roof to take a look, but not while it is wet. There could be issues with the cowl and/or pointing.

Leif

iamcornholio wrote: »

You need to coat it with a stain block first

I have some Zinsser 123 lying around.

keystone

You need to sort out where its coming in first as you suspect. Then the 123 will deal with it internally once its dried out.

Cheers

nickj_2

i find that 123 isn't that great at covering water stains , some solvent based undercoat would be better , if not a bit of stain block