Plasterboard re-fixing

[PeterC]

My upstairs ceiling has always had cracks between the boards - not helped by being so close to the West Coast Main Line! Now that the line has been 'upgraded' and the lines have rubber pads under them, it seems to be worth having [another] go. My father spent years trying to seal the cracks, so in some places there's a build-up of whatever he used.

I bought a box of dry-wall screws (38x3.5) - having 1000 of 'em I'd like to use a few. Tried running some in with the portable drill; went in OK, stopped just below flush but the edge of the board cracks. Also the joints aren't all central on the joists, so there could be 3 - 4cm one side and 2 - 1cm the other. Before I perforate the whole damned sheet, please advise me on how to do this. If necessary I'll drill and c/sink the holes.

[Dave Plowman (News)]

More likely caused by movement in the timber it's attached to.

[The Medway Handyman]

Have you tried 'jacking up' the plasterboard to meet the underside of the joists?

[NT]

When the board cracks its often because youre putting the screw in too close to the board edge. The other point is not to countersink them at all, make them dead flush, again less chance of cracking.

NT

[PeterC]

Possibly for most, but some is actually down a bit (mm or so) relative to the adjacent board.

[PeterC]

'tis a thought, but there's still the problem of being too close to the edge where the joist isn't in the middle.

[PeterC]

Yes, but if the p/b is only a cm or so over the joist there's not much choice. I'm trying to get them flush but that in itself is cracking the board. I might have a go at putting in a flush countersink and propping the board, so that the only starin is the weight.

[NT]

If you mean countersinking and predrilling each hole, in extremis that does help, and sounds like it may be worth it for you.

NT

[george (dicegeorge)]

My joists are very uneven so I screwed thin battens under the joists then fixed plasterboard to the battens many of which i managed to attach at the exact width of the plassterboard so I didnt have to trim the edges.

[g]

[PeterC]

Yes. A bit slow, but I'd need fewer screws anyway, as they should be better at holding. Doing it this way, I can push the board upwards with one hand whilst running in the screw.

[PeterC]

Good move for new boards - not on for existing ones. It might be worth me putting some extra timber where the overlap is really poor, otherwise the screw would have to be at an angle!

[NT]

It sounds like youre out of other faster options. Any fixing that breaks the board up will make things worse rather than better.

There is another way, but probably not warranted in your case. Prop the ceiling up using timber uprights and sheets of whatever, then lift some floorboards above and pour a thin plaster mix on.

NT

[PeterC]

Hadn't thought of that - thanks. It's actually a case of lifting the insulation, as this is to the loft.