Ceiling showing marking

If the ceiling has ever got wet in the past, the brown stain will always show through emulsion even if there is no current leek (or even a leak!)

The trick is to paint it with an oil-based paint - white oil-based undercoat is fine. Once that is dry, you can *then* apply a final coat of emulsion, and the stain won't re-appear.

Thanks Roger, actually after posing this question I realised that I had the wrong corner in my mind. The corner above once had a fire place in it, so there are definitely no piping underneath. However whoever removed the fire did not put an air brick in, though it does not feel damp, as the concrete base is still in place there is not much I can do about it. I will try your idea, will it still work painting over the are on top of the two layers of paper and the emulsion? I did wonder if PVA might solve it.

I've had several call outs to investigate 'leaks' that were simply old leak stainms bleeding through emulsion paint. Coat of Stain Block will sort it

What's with the grease? (Probly cut&paste error...)

Thomas Prufer

"Overcoat in 4 hours" maybe gives it the edge over ordinary oil based undercoat if you're in a hurry