Damp where chimney was

[AM349]

Hi

I live in a mid terraced house and have had my chimney taken out recently. Since then the wall has been plastered and dried out, but every time it rains a wet patch appears about a meter high in the exact area where the chimney use to be.

The floor is solid but the area around the old chimney breast has been filled with sand only.

The neighbours still have their chimney and a fire on the opposite side of the wall.

Could anyone shed some light on this matter?

 

[noseall]

it could be a problem of a hygroscopic nature

 

[Joe Malone]

it could be a problem of a hygroscopic nature

Unlikely, not if the damp patch appears every time it rains. It's more likely water ingress. Was the chimney capped off and ventilated when you removed the chimney breast?

 

[davebelushi]

it is likely to be salt and carbon deposits. these are hygroscopic by nature and as such during rainfall, when the reletive humidity is higher, the areas in question will naturally be more defined.

re render using a salt resistant mix or dry line.

 

[noseall]

areas of masonry that are saturated with hygroscopic salts, behave relative to humidity levels in the air.

this phenomenon was made obvious when a dabbed wall i had worked on, would clearly show the dabs when it was raining or humid. the dabs local to the offending area were the only ones to show.