Plaster blowing over screws

stgermain

Morning All
I hope somebody can offer advice and thanks in advance for viewing. 
The ceiling of my newly-built extension was boarded and skimmed over a year ago. The plaster has blown a few times over the drywall screws in several places, despite my refilling with easifill, misting and repainting (and experimenting with priming the screw heads and using pva on some sections to help adhesion). I'm assuming I probably need to look for the battens (or make some educated guesses as to where they are) and sink more screws in around the repeat offenders before attempting to refill a third time in some instances but just wanted to check this was worth a try before doing so. 
The pops are worse in the summer so I'm guessing the timber and/or plasterboard is expanding but even if the roof timbers were damp when put up, I'd expect these to have dried out after 18 months. Any recommendations would be most welcome. 
Thanks

ComicGeek

I have the same problem with some of mine (6 months old) so interested to hear thoughts. 

Mine look like this currently, haven't done anything yet to repair them. Mine are only in the area where I've had new floor joists installed above.

Jeepers_Creepers

You both have an 'upstairs'? Do you think it's caused by footfall or just movement in the timbers?

The only thing I could suggest, you have already tried to some degree, stgermain; unscrew each miscreant, coat thread liberally with PVA, try and inject a good dose more up t'hole (use a small narrow-nozzled PVA bottle), and reinsert screw. This will hopefully both glue the p'board to the timber joist above, and also glue the screw thread to the p'board. Both should seriously reduce any subsequent movement.

stuart45

There are a number of reasons why you get problems with the screws.
The screws went too deep through the paper. Best to use a depth stop bit.
Screws too short.
Not enough screws.
Studs or joints not lining up properly causing the boards to pull on the screws.
Expansion of contraction of the studs or boards.
I worked with a New Zealand Chippie who always glued and screwed.
Said it was standard there.

FreeBear

The whole point of using screws is that they don't pop like nails do. If there is movement causing "pops", it suggests that the boards are not being pulled firmly against the joists. Tightening the screws up might help, but you don't want to be driving them in too deep - Just enough to be slightly below the surface without breaking the paper on the PB.

In situations where slight movement is anticipated, some people will apply a grab adhesive to the joists or battens before fixing the plasterboard in place - A belt & braces approach, but too late for the OP.

Jeepers_Creepers

Inject PVA...

NSG666

As you need to fill them anyway it can't hurt to put some additional plasterboard screws at either side of them 38mm (min) and probably best put in by hand so you don't go too far into the plasterboard.

FreeBear

Jeepers_Creepers said: Inject PVA...

PVA doesn't have very good gap filling qualities. If the PB is fairly tight up against the supporting timbers, there won't be much space for it to flow out so won't provide much in the way of additional support.

If there is a gap between the PB and joists/battens, a thinned down grab adhesive would be more suitable - Use a solvent-free type that can be thinned with water. I wouldn't recommend using an expanding foam adhesive as this is likely to do more damage is it foams up and sets.

stuart45

NSG666 said:

As you need to fill them anyway it can't hurt to put some additional plasterboard screws at either side of them 38mm (min) and probably best put in by hand so you don't go too far into the plasterboard.

I normally do this.

ComicGeek

Looking closer, I can see some settlement cracks around the top of the external walls, so I'm guessing that it's just due to general settlement for me. It's only where the new floor joists are - the rest of the large room was reboarded and plastered at the same time (same spacing, screws, method etc), but doesn't have any new joists or walls, so has already finished settling many years ago

But interested in hearing what works for the OP, as I only want to do the job once! I'm probably going to wait another 6 months for everything to finish settling, or longer if needs be.

Rosa_Damascena

FreeBear said:

Jeepers_Creepers said: Inject PVA...

PVA doesn't have very good gap filling qualities. If the PB is fairly tight up against the supporting timbers, there won't be much space for it to flow out so won't provide much in the way of additional support.

If there is a gap between the PB and joists/battens, a thinned down grab adhesive would be more suitable - Use a solvent-free type that can be thinned with water. I wouldn't recommend using an expanding foam adhesive as this is likely to do more damage is it foams up and sets.

I think Jeeps was having a humorous moment...