Water through ceiling.

[Bayliss]

We had a fault with the water works and resulted in water coming through our living room ceiling. The fault is now fixed, we stripped off the damaged ceiling paper expecting to find plaster board requiring replacement. Lucky us finding lath and plaster, and the plaster has dried out simply leaving heavy water staining. Should I now seal the plaster prior to using a emulsion paint, what is the correct way forward?

 

[Flyfisher]

I don't know the answer but I'm very interested to find out because we had a similar event earlier this year, though fortunately the room was awaiting decoration so the fact that the ceiling paper mostly fell off of its own accord didn't really matter.

I was dreading the damage that might have been done to the ceiling lath & plaster, but it seems to have dried out without any apparent harm, apart from some water staining.

When we had a similar thing happen in a previous modern house (well, 1950s) the plasterboard was completely ruined and large bits fell down.

These old houses are more resilient than they might first appear!

 

[robgil]

I would wait for it to dry properly or you will see staining coming through the paint. There are undercoats designed for this type of application.

 

[Bayliss]

Good point, thanks Robgil.

 

[Lime]

I would wait for it to dry properly or you will see staining coming through the paint. ...................

Then I'd wash the ceiling.
See what it looks like and go from there.

 

[Feltwell]

Lath & plaster ceilings are generally OK if it's a one-off event, whereas plasterboard is normally ruined.

I was lucky here - our plasterboard kitchen ceiling survived a leak as it's foil backed plasterboard.

We've had a couple of other leaks above lath & plaster ceilings and they've been fine.

 

[Bayliss]

I've purchased some 'stain blocking' paint as suggested, the ceiling is still a bit damp in the lowest part where the water pooled before dripping through. Its been over a week with windows open but I think it will be another week before its proper dry. The plaster is a bit cracked with quite a few dimples and crevices, full of character which the paper had previously hid.

 

[MdB]

Stainblock is basically latex I believe and will therefore will trap any moisture still in your ceiling. I would therefore make sure the damp has completely gone before you use it.

 

[jocelyn plummer]

And despite the latex it is very drippy to apply---horrid stuff-- and the stains seem to reappear after a while.