Help! Didnt seal plaster before we painted

dave82_2

It is my understanding that you must PVA old skim work before applying a new skim coat for the following reason:-

In the same way plaster sucks moisture out of paint it sucks moisture out of fresh plaster.

The PVA isn't to help the adheasion of the new skim coat of plaster it is to stop the old plaster sucking all the moisture out causing it to crack and fail.

cyclonebri1

dave82 wrote: »

It is my understanding that you must PVA old skim work before applying a new skim coat for the following reason:-

In the same way plaster sucks moisture out of paint it sucks moisture out of fresh plaster.

The PVA isn't to help the adheasion of the new skim coat of plaster it is to stop the old plaster sucking all the moisture out causing it to crack and fail.

Exactly, and that's how any plaster would see it, but,

Unfortunately the householder is left with the situation we are discussing???????????????????????????

dave82_2

Is there an alternative to PVA when skiming ontop of old skim or render? Bit worried as we have just had our whole house reskimmed and pvad first! Not planning to put any wallpaper up though so won't be going near it with a steamer!

misgrace

Dave, PVA is meant to be used before you plaster, you PVA the old brick/wall/ceiling then you skim with plaster, thats it, never PVA new or bare plaster prior to painting.

cyclonebri1

dave82 wrote: »

Is there an alternative to PVA when skiming ontop of old skim or render? Bit worried as we have just had our whole house reskimmed and pvad first! Not planning to put any wallpaper up though so won't be going near it with a steamer!

You could sand the whole lot but:eek: what a mess, so pva is very convenient/cost effective;). It simply has it's limits and the liabilities we've gone through.:beer:

If you want some real horror stories search out the issues on "thetilersforum", they hate the stuff.

dave82_2

misgrace wrote: »

Dave, PVA is meant to be used before you plaster, you PVA the old brick/wall/ceiling then you skim with plaster, thats it, never PVA new or bare plaster prior to painting.

I know that but cyclonebri1 seems to be suggesting it is a bad idea to PVA before plastering.

dave82_2

cyclonebri1 wrote: »

You could sand the whole lot but:eek: what a mess, so pva is very convenient/cost effective;). It simply has it's limits and the liabilities we've gone through.:beer:

If you want some real horror stories search out the issues on "thetilersforum", they hate the stuff.

Don't really see how sanding would help that would just take me back to the render which would also need sealed with PVA otherwise it would suck the moisture out the new skim coat as well?

Not trying to arguee about the limitations of PVA just wondering what the alternative is before palstering and it doesn't seem like there is one?

I am pretty sure the problem with tiling is if you PVA ontop of the new plaster rather than pva then skim?

cyclonebri1

dave82 wrote: »

I know that but cyclonebri1 seems to be suggesting it is a bad idea to PVA before plastering.

No chap, I was only ever talking about skimming, or more correctly I think I referred to it as re-skimming?, ie, not plastering bare walls but walls that have previously been finished, posibly painted, wallpapered etc.

To be honest if moisture ever got through full depth plaster to your block/brickwork you'd have more to worry about than was it pva'd;)

cyclonebri1

dave82 wrote: »

Don't really see how sanding would help that would just take me back to the render which would also need sealed with PVA otherwise it would suck the moisture out the new skim coat as well?

Not trying to arguee about the limitations of PVA just wondering what the alternative is before palstering and it doesn't seem like there is one?

I am pretty sure the problem with tiling is if you PVA ontop of the new plaster rather than pva then skim?

Not suggesting sanding the lot off, and to be honest I wouldn't even try to key the surface which was my suggestion because of the mess, but it would allow the wall to be wet down to aid keying.

And again I don't think the issue with skimming old walls is to much suction, it's the exact opposite, they will have been sealed that many times with limewash, emulsion, paste etc the issue will be to get a key into the surface hence the use of pva.

Don't get me wrong, I'm not decrying it, I am simply saying it has to be used with just a little reasoning as to future use, which is worlds apart depending if you are the plasterer or the homeowner,

dave82_2

Fair enough just my missunderstanding I think!