multifinish over multifinish, how soon?

[diy_dave1978]

Hi,
I skimmed a wall but ended up with a slight bow into the wall which I think I can correct with another thin application of multifinish plaster. Essentially, it's not quite flat. I guess my preparation was insufficient.

I left it two weeks, applied liberal amount of 2:1 PVA, let it dry overnight and then more PVA before the attempting the skim.

As I was putting on the first (scratch) coat, within a few minutes of starting, cracks started to appear in the wet plaster. They were quite big. No way would it have been a decent finish. So I scraped it straight off.

Was two weeks too soon? Could I have used too much diluted PVA?

Are cracks are only caused when the background is too absorbent, or are there other reasons?

I'm just a DIY'er.

Any advice would be appreciated. Unfortunately I didn't think to take photos.

Thanks,
Dave.

 

[bobasd]

suction is the first suspect but there are other possible causes of cracking and crazing.
pics would really help?
the cause(s) could be due to the first skimming or the later application of multi-finish?
whats the background?

 

[diy_dave1978]

Hi,
I scraped off the still wet scratch coat after I saw the cracks forming. I didn't take photos.

It seems to be dot n dab plasterboard.

When I first got to it, it was uneven and had patches of undercoat plaster.

I levelled what I could with bonding plaster. Then I skimmed with multifinish. That coat was fine.

Two weeks later I tried to skim again to take out slight undulations, but as described above, cracks appeared within a few minutes. Not crazing, but cracks.

Is PVA sufficient to limit the suction?

Thanks,
Dave.

 

[bobasd]

Dave, this isn't criticism, i know your a DIY'er but this might help you and others in future

its common for DIY'ers to think D&D is the easy way to go but the first thing that can go south is the plumb and plane flatness of the boards - next comes trying to pull the surface out to a plumb and plane flatness with coats of plaster that would perhaps have been more suitable for solid plastering the wall in the first place - no D&D would have been needed.

for all i know none of your coats have taken - if thats the case then it might be best to think about either trying to scrape back to plasterboard paper (good luck) or pulling the whole lot down and starting again or getting in a plasterer to give you a heads up on site or maybe to simply do the job.

 

[diy_dave1978]

Hi bobasd,
I didn't do the dot n dab.

Believe me, I wish I had ripped the thing off in the first place.

Thanks for your help.

Dave.