painting where new plaster joins old

[mattc1]

We've just had some building work done and there are a number of places where new plasterwork joins old plasterwork i.e halfway along a wall the new plasterwork meets old plaster and has been gently merged in. Obviously, where the two overlap the new plaster becomes very thin as it has been fanned out to make the joint smooth. The problem is that when we paint the wall (using watered down emulsion), at the point of the joint, the thin plaster keeps peeling off as it is so thin and is waterlogged by the emulsion.

We've sanded back the very, very thin plaster but can't sand it any more as there will then be a lip between the two. Is there any product we can apply to stop the thin plaster from peeling away when painted? Any other tips gratefully received.

Matt

 

[Richard C]

It’s not been done correctly; your spread has either not prepped the old plaster correctly or used too much water which destroys the plaster & leads to exactly what your experiencing. You need to take all the flaky plaster off the old wall, prep the wall (but don’t get PVA on the wall that’s to be painted), apply a layer of Easyfill between the two & sand the transition down again; or call the spread back & tell him you expect him to do it.

To be honest finish plaster is not well suited to blending in & you’re still likely to see the join. I always recommend re-skimming the entire wall after such repairs or bricking up doorways etc. it's not much extra work & can actually be quicker than trying to blend it all in, when correctly done you will never see the join.

 

[dcdec]

Thats excellent advice from Richard C.

I had exactly the same on a job last year and couldn't understand why the plasterer hadn't done the whole wall, half of it looked lovely (the extension) and the other half (existing) was completely battered, i skimmed it with easifill and didn't look as nice as the newly plastered bit.
I do wonder whats going through the minds of these trades sometimes, i wouldn't paint half a ceiling, i'd do it all even if i didn't get paid for it, the job satisfaction is worth it, i guess the stinginess of some clients plays a part though, you suggest the best thing to do and they want to save a few quid to the detriment of the job.

 

[mattc1]

many thanks for the replies. That's pretty much what I thought.

Matt