Damp spots after painting

[KMH497]

Hello,

I’ve recently moved into a 300-year-old cottage which, due to its age, does not have a damp course. Before I moved in, there were no visible signs of damp on the paintwork. However, within days of repainting the walls, several dark patches have started to appear—particularly on the walls and above the kitchen tiles. These patches tend to fade when heat is applied. There are no known leaks or ingress of water.

Has anyone experienced something similar or have any advice on how best to treat this?

 

[opps]

It might be the case that the original paint was a breathable lime paint.

I tend to work in Victorian houses, which, although solid 9" walls, do have slate DPCs.

Hopefully someone else familiar with properties like yours will be able to advise further.

 

[Ollyfp]

Are you painting internal dividing walls or the main walls of your house? If any of the walls incorporate a chimney breast, salts can present a problem.

 

[Scally-Ho]

If you are using a vinyl type of emulsion paint, that could be your problem. Leyland Trade Super Leytex allows the substrate to 'breathe' and therefore any moisture will evaporate as the days pass. This won't work if you apply over an existing vinyl paint and that will have to be removed first.
"The Leyland Trade Super Leytex Paint is a full-bodied and quick-drying paint, ideal for new plaster, providing a high-opacity, breathable layer that allows fresh surfaces to dry out properly. With excellent coverage and a permeable film, it ensures new plaster can breathe while delivering a smooth, uniform finish. The paint is recoatable in just 2-4 hours and offers a generous coverage, making this paint a reliable and efficient choice for everyone"

 

[accelerator]

What paint did you use? Please specify exactly.