Ceiling showing marking

[Broadback]

I have removed polystyrene tiles from kitchen ceiling, lines, papered and emulsioned. After about three weeks one corner is looking brown, I cannot feel any damp. The area is below where there was an airing cupboard in the room above, until I removed it several months ago (the airing cupboard not the room ;-) ). Now it may be that the central heating pipe above is leaking, though the pressure is not dropping on the combi boiler. The problem is that it is my daughters house 50 miles away, so I want to resolve it, if possible, in one visit. I will take up the floor boards upstairs and look for a leek, if there is problem solved. However it is possible that the stain is working through from a previous problem, if so what is the solution please?

[Roger Mills]

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.

[Broadback]

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.

[The Medway Handyman]

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

[Thomas Prufer]

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

Thomas Prufer

[Stuart Noble]

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