No Primer Needed For Plaster

[delboyeee]

I've got a guy plastering and then is to paint a room for me. I've been assured that he's good and his work so far is very crisp.

The only thing that has confused me slightly is he reckons that the type of plaster he uses does not require any primer or undercoat at all, just two top coats.

Are there types of plaster that do not require any under at all?

I forgot to mention I know nothing about plaster at all, just have repeatedly read that newly plastered walls MUST be primed as to prevent the wall absorbing the paint.

 

[Richard C]

I'd be very surprised but what's he using? You should always prime new plaster or the paint wont stick properly; 2 – 3 coats of matt white thinned with 25% water will be fine but the new plaster must be allowed to dry out around 10 days before painting.

 

[delboyeee]

Cheers Richard, he will be painting after 2 days drying with no primer. I'll try and find out what type of plaster he's using, but your telling me it's unlikely 2 coats of a darker colour matte will not finish properly?

 

[Richard C]

New plaster is very porous & unless the paint is thinned, the plaster will suck all the water from it before it has a chance to stick to the walls. The result is that the paint may crack & peel once it dries out thoroughly. Even if it doesn’t, it’s likely that any wall paper applied in the future will pull it off when stripped back for redecorating; maybe not a problem for you but certainly will be for someone!

He may be using a trade breathable emulsion which can be applied directly to new plaster once it’s sufficiently dry (light pink or grey) but even that should be thinned 25% for the initial coats to prime the plaster first. If it’s conventional emulsion paint, it should be left around 10 days as I said before; if the paint is applied too early you could get blistering as any moisture still present comes to the surface & tries to find a way through.

 

[delboyeee]

The plaster being used is multi finish, he says he's going to use an emulsion as an undercoat, but reckons that it would be alright.

 

[Richard C]

Multi Finish is a standard finishing plaster; practically everyone uses it including me. Ordinary white matt emulsion is fine as a primer/undercoat but the first couple of coats should be thinned around 25% or it won’t stick to the plaster properly. If he’s using ordinary emulsion, 2 days is really too early to be painting a newly skimmed wall; you should leave it a minimum of 7 days but 10 would be better; it’s 4 weeks drying time for a full base coat with skim finish.

Have a read here;
http://www.diydoctor.org.uk/projects/paintnewplaster.htm

 

[delboyeee]

Cheers Richard,

So basically, he should not be painting that early no matter what he's using?

I'm very confused as he assures me he has done this a thousand times and it's fine.

What is the process to correct it if it does go wrong, e.g. paint peels and cracks, does this affect the integrity of the plaster or is it just the paint job that gets spoilt?

 

[Richard C]

So basically, he should not be painting that early no matter what he's using?

If he’s using a breathable emulsion then should be OK; ordinary emulsion I would wait as I said. Read the link I posted & a Google search will throw up much advice in the same vein; we can’t all be wrong!

I'm very confused as he assures me he has done this a thousand times and its fine.

You’ve only got his word for it & I’ve no way of knowing that; perhaps he’s been very lucky.

What is the process to correct it if it does go wrong, e.g. paint peels and cracks,

Yes; it may also peel off if you stick selotape to it, this is a little test you can use to check how well the paint is stuck to the wall.

does this affect the integrity of the plaster?

No but if the paint starts peeling, it’s a hell of a job getting all the old paint off the wall before you can re-decorate again.

 

[delboyeee]

Cheers old boy, you've been very helpful.

 

[roughcaster]

Cheers old boy,

you've been very helpful.

And you telling us your 21 Rich'.

Roughcaster.