blown plaster? why?

[sentinal73]

Hi

About a year ago i had my living room skimmed, the guys PVAd the old walls and skimmed

I did wait a few weeks before i applied a mist coat and then a few layers of paint.

Anyway, have just drilled into the plaster to fit some speaker brackets and a lot of the skimmed plaster has fallen off, must be about a square meter ! you can pick at it and it just comes away from the wall

Why might this be happening? will it all have to be removed and re-done?

oh, and i've lost the plasterers number so cant get him back to sort it out!! grrr

thanks anyway

 

[trowelmonkey1]

well sounds like you waited more than long enough before painting so don't think it's anything you've done.

any damp in the wall? what type of brick/block? is it just the skim coat or the backing plaster too?

 

[sentinal73]

i dont beleive that there is any damp, its on 2 different walls, one and internal one, the other a joining wall with next door.

sorry dont know the name for the bricks/blocks, but my guess is that they are block, and black in color, and quite soft

the original plaster is still in place, so its just the skim that is falling off,

will i have to remove the lot and replaster it ??

 

[dave1953]

Totally agree with T.M, if it's just the skim blown then the undercoat was'nt scratched or prepared properly or if the undercoat has blown as well then you may have a underlying damp problem

 

[dextrous]

Hmm, not pleasant. Think the only immediate solution will be to patch up the area (skim) and try to support the rest of the wall by using lining paper. Not ideal, but a quick fix.

 

[Richard C]

The skim clearly hasn’t adhered sufficiently; was it a re-skim over the original plaster? If so what type of paint (or anything else) was on there? Was the wall a hotch potch of repaired backgrounds?

 

[dave1953]

I'me thinking clinker blocks from your desciption, normally built at skirting, dado and picture rail height for ease of fixings, they are not the best at breathing to maintain dry wall areas but there still could be an underlying problem within the area described.I would hack off the entire affected area to have a good look.

 

[joe-90]

Doesn't sound like it's been prepared properly to me. PVA too weak? Plaster sticks to plastic buckets so there's no excuse for it not sticking to the wall.

 

[Micilin]

Is there a sheen on the exposed bit ? - maybe they let the PVA go dry before getting the finish on that bit.

A lot of blokes think PVA is some kind of magic stuff.

 

[sentinal73]

it was a skim over the old plaster

the old plaster had been painted with emulsion paint.

no serious repair to the old plaster, all is original plaster

 

[Micilin]

Is there paint on the back of the piece that fell off?

 

[sentinal73]

Micilin - think that might be a clue

are they supposed to plaster the walls whilst the PVA is still wet? or wait until it is dry?

I do rememeber that they PVAd it one day, and plastered it the next

and yes, i can see a slight sheen, can see the PVA a little on the old laster where the new plaster has been removed

 

[sentinal73]

Micilin - yes , there is paint on back of the peices that have fallen off

 

[Micilin]

First guess is that the spread has plastered onto tacky PVA as he should have, as the new skim is stuck to the paint, and the paint has come away from the old plaster.

However, did he seal the wall with PVA the day before? If not, the moisture from the replastering would have wet the paint and weakened the adhesion between it and the wall.

He should have checked to see if the background was sound - ie paint not flaking or loose.

He should have scored the surface , or sparrowpicked it, before applying the PVA to give a physical key as well as a chemical one.

 

[Micilin]

I think my replies have crossed your posts!

Just to clarify - is it OLD paint on the BACK of the bit that fell off?

On exposed surface, you can see a sheen -is this over old paint?