Raking out hairline cracks in plasterboard ceiling

[Merryterry]

I am just about to fill some hairline cracks in a plasterboard ceiling. For years I have just been forcing in polyfilla type filler into the cracks with a finger, letting it dry and sanding down.

The cracks reappear after a couple of years.

I did read that a way of permanently doing this was to rake out the crack leaving a vee shaped groove before filling. This makes sense to me as it means that the filler has a larger surface area to adhere to.

Any idea of a good tool to leave a vee shaped groove in plasterboard?

Or alternatively any other way of doing it?

[Ian Stirling]

I've found a stanley knife is effective. You cut a V - starting on one side of the crack, scoring to a depth of

2mm or so, repeat on the other side, then deepen the cuts with successive scores till they meet in a 'v'.

[Jim Alexander]

Stanley knife, but if the crack is along a joint it suggests the joint wasn't taped. If the cracks are randomly located something is going wrong or its not plasterboard.

Jim A

[PeTe33]

Nah, if the joint wasn't taped the plaster would have fallen out. The tape doesn't stop it cracking, but it does stop plaster dropping on your head.

Our ceilings were done in 12mm board, all taped before skimming. The hairline cracks appeared to a degree even before we started bouncing around in the roof running cables and stuff.

I thought there was one chap on here who had a trick with pipe lagging and "injecting" PVA into the crack.... Might be worth a quick google.

[meow2222]

If cracks appear its due to movement, and making the crack bigger isnt going to have any effect on movement. A finger along the line is a lot less work.

FWIW if you use distemper instead of emulsion you wont need to fill the hairline cracks as the paint will do it as it goes on.

NT

[Stuart]

Should the V not be pointing down with the widest part at the top so the filler will ( hopefully) remain in the gap.?

[robert]

Brush on crack filler works surprisingly well. Robert

[Roger Mills]

Do you just apply that without needing to rake out the cracks? Where do you get it?

[Ian Stirling]

Any hole in the wall shop.

[robert]

Yes just paint on. Was very sceptical when I first saw it . Robert

[Rob]

There is and it works. Only I found it easier to buy the PVA in a=20 flexible plastic container, cut the nozzle with a slant and inject the pva=20 into the crack. direct from the pack. Never had a problem since.

[PhilB]

10 years on but you're absolutely right Stuart!