Damp Seal Issue?

[David Shellman]

Hi all, I live in a terraced house which was built at the beginning of the last century. A damp proofing course was carried out on my front and rear walls around eight years ago, however I recently noticed a few greasy looking stains appearing on the front internal wall. I liberally applied some Thomson's Damp Seal and then, when dry, a dulux emulsion. After a day a dark stain appeared around the edges which has now started to bubble. I have attached a photo and any suggestions as to what it is would be appreciated. Thanks.

 

[sparkwright]

Was the product oil-based or water-based?

Has it been raining?

You say this is a front internal wall? Do you mean the inside part of a brick cavity wall??

 

[David Shellman]

It's a flammable product so I would assume it's oil based. It's a stone built terraced house and I had problems with rising damp prior to the damp proofing course. It's highly unlikely that rain has anything to do with it.