Damp Under Window Sill (2026)

Don’t just paint over it! The problem will come back. 1️⃣ Check the exterior sealant for cracks. 2️⃣ Improve ventilation in the room. 3️⃣ If the plaster is soft, you may need a professional to treat the area.

If you’ve done all the above and the damp returns within a month, or you see a white, fluffy salt deposit (efflorescence) on the sill, your problem is structural. Likely causes: damp under window sill

Spotted discolouration, peeling paint, or black mould under your window sill? It’s easy to ignore, but "damp under the sill" is one of the most common red flags in a home. Don’t just paint over it