Dot & Dab Marks Visible Through Plaster & .........H Ask your questions and find answers on many subjects relating to plastering and dry lining

[charliesdad]

I have had an outside wall plastered with the Dot & Dab method, & now after about 6 months the black areas where the dot & dabs were applied are clearly visible through the plasterboard, plaster & 2 coats of paint. The wall now looks like it has a dose of very large black spot - Please help.

[kbrownie]

did you external wall have damp problems?
KB

[charliesdad]

The wall was fine for about a year, then all of a sudden, these dot & dab patches can be seen. The wall was initially an outside wall of a drive thru carport, with a bedroom extension above. Both ends of the carport were then glazed to form a room. Radiators provide the heating, so I know it is not condensation. I could understand if the dot & dab was being used to bridge the damp, however the walls surface shows no sign of damp at all.
Any Ideas....?? - Thanks for your help in advance.

[kbrownie]

Was this wall a single skin or a cavity wall. If single skin wall it should have been treated prior to fixing boards.
KB

[charliesdad]

OK thanks, I believe the wall is single skin, there is however a second wall, but its not a closed cavity. this second wall belongs to next door but the gap is only about 2 inches.
Assuming I have to take it back to the brick - what do I have to treat it with, & is there an anti damp/fungal additive for the dot & dab mix. ??

Thanks for your help in advance.

[kbrownie]

have a look at projects page "wall linings" may be helpful
KB