plasterboard ceiling repair

[Sam]

Hello,

A "bubble" appeared on our kitchen ceiling. When I touched it, it disintegrated in my hands. The bath is directly above and I think a very slow drip has gradually soaked into the plasterboard and softened it. I have cut out the offending square and put battens on the joists and screwed a new square onto that, but it's not quite flush in one corner and the old board seems to sag in the middle. Should I have fitted a batten across the joists as well as to the sides? Should I have supported the edge of the old board?

What is the recommended distance between screws? I have tried to screw the old board onto the joists but the edge of the board is a bit crumbly so it's been a bit hit and miss.

Thanks.

[The Medway Handyman]

Have you sorted the drip out?

You need to cut out a larger area to include any sags. Cut away any suspect board to leave a gap half the joist width.

[The Natural Philosopher]

• screw bits of batten behind old plasterboard and screw new into them for all round even support.

[1501]

He'd be a drip not to.

[Sam]

That's the strangest thing. The bath is bone dry. I have had it filled with water and I've checked the trap and waste and there's no leak there. I've overflowed it but no leak there either. I thought the overflow was a prime candidate because the pipe just pushes on; there's nothing to hold it in place.

We changed the bath a couple of months ago. I think perhaps the old bath leaked for some time; the ceiling has always looked a little suspect but I've never touched it until now.

When I did touch it, it crumbled but was dry, which makes me think the leak had stopped but the damage had been done.

I'm a bit puzzled about this: surely you cut it to the full width between the joists, not halfway?

[Geo]

• 1/2 the width of the joist...(each side)?

Geo

[The Medway Handyman]

Sorry, cut the board at the middle of each joist.

l l l Joist l l l l l l__________l_____________________ l_____________Board_________

Thus leaving room for the new board to be screwed to the joist.

[Stuart Noble]

Often quicker to saw cut flush with the joist and screw a couple of battens to it.

[Sam]

Sorry for the late reply. Thanks, I understand now. A bit like cutting across the middle of a joist when replacing a section of floorboard. It's strange, I've never done that on the other side of the joist; when repairing plasterboard I've always fitted battens... not that I do it that often!