ridges between plasterboard

[Hib]

Hi all,

can anyone tell me what causes the ridges to appear between sheets of plasterboard on the ceiling after they've been skimmed (usually about 2-3 mm x 2-3 mm along the line of the edge of the board).

I've seen them re-taped over and recovered with jointing compound (all on top of the original finish) only to reappear again shortly afterwards.

What causes it and how do i get rid of it?

Cheers for your help.

Hib

 

[regsmyth]

Do you mean the plaster cracks and you end up with a 3mm gap, with one edge lower than the other?

 

[Hib]

(yeah - i'm a spoilsport - i edited out that last post)

You know what Regs, you might well be right. there does seem to be a bit of movement and it probably is more a crack than a ridge (looking like a ridge to someone who doesn't look closely enough ).

I'll leave my ridge theory unedited just in case there's anyone who'll second it - but i kind of doubt it. Your explanation sounds right.

 

[gregers]

was the board scrimmed?

 

[Micilin]

If there is a large gap , and you skim over it without letting the first coat pick up a bit, then there wii be a ridge because that bit of finish will be set diffrently than the rest of the skim coat. This will also happen if there is a bit of movement.

To avoid this, fill all scrims first and let it pick up a bit before appyilng first coat of skim. Or , fill all scrims with gaps before hand with a bit of joint filler or easi fill so that your skim coat is uniform thickess.

These ridges can be got rid of in a few ways

- you can pull the back of the trowel along them to scrape them off , when the stuff picks up a bit, before the last trowel.

- you can give them a rub of a sponge float when it has picked up a bit, then trowel

- you can let it set , and when dry, scrape them with the back of the trowel and filla bit with easifill or aimes if needed.

- when dry enough to sandpaper, simply sand them off, again if you need to , use a bit of easifill,aimes or what you have to hand.

 

[Hib]

was the board scrimmed?

Yes , it was scrimmed. Thanks Gregers

Cheers for the info as well Micilin, appreciated.

Hib