Painting new plaster? Standard emulsion?

[Le Gavroche]

I have finally had my garage plastered out, and want to paint it white.

A mate of mine who is a builder said I need to water down emulsion and apply a couple of coats of diluted paint as it will soak in, then apply the 100% emulsion on top. He motioned something about the paint possibly peeling off if 100% emulsion is applied directly to bare plaster.

The plaster said this was bullst, and to simply buy a decent quality emulation (He suggested Dulux) and simply roller it on like a standard coat without watering it down. He also said "You'll be there forever if you keep applying diluted coats as it'll just keep being drawn into the plaster".

Anyone got any thoughts on this??

Edited by Le Gavroche on Friday 13th June 12:36

[bangerhoarder]

Never really tested if it was nonsense - I've always done the first coat as a 50/50 mix. It ends up being pretty light and patchy, but then not had issues afterwards.

I've never used Dulux on bare plaster, and I generally never use it now - just decent trade paint.

[JoshSm]

I'd trust a plasterer to plaster, not to decorate.

Even if a mist coat was unnecessary it's not like a lot of time or effort is involved in doing it.

You could jump straight to slathering on the good expensive paint on the assumption itll be fine, but you'll be in a world of pain if it goes wrong, while an unnecessary cheap mist coat doesn't really you lose anything.

[LennyM1984]

Doing a mist coat (the diluted emulsion) is really quick and easy and has always been recommended to me. I don't think the idea is to try and dry out the plaster, it is to draw the paint into the plaster to give your proper coat something to key onto.

You only really need to do a single mist coat so why not.

I just use diluted contract matt - As I understand it, it doesn't include some of the vinyl binders(?) and so is ideal for this type of use case.

[Cow Corner]

I can’t imagine that decorators routinely apply mist 50/50 mist coats for fun

[Le Gavroche]

Seems mist coat is the consensus. I shall do that. Thanks

[The Gauge]

A mate of mine has worked in the paint industry for years and he always advises using a watered down paint mix on new plater, to let it soak in, then normal coats on top and to never use PVA to seal new plaster, you don't want to seal it or there's a chance the paint can peel off.

[curvature]

Mist coats are still applied in all of the construction sites that I visit, it's good practice.

If you don't and the paint flakes it will be a nightmare to try and stop and subsequently repaint.

[Ryyy]

I've had 95% of my house plastered and about 90% of them walls have been painted straight onto with white leyland trade vinyl matte. Been fine up until now and it's been on a few years now.be reyt.

[PhilboSE]

The plaster (or more likely hardwall) on your garage will suck the water out of the paint emulsion, preventing it from drying and adhering properly, leading to cracking and flaking later which will be very hard to patch and look good.

Just follow the paint instructions for a mist cost on fresh plaster, personally I find 50:50 too runny and consequently messy. I dilute to about 70:30, not had a problem yet. Use the same paint you intend to use for other coats, I find using direct to plaster paint or contract matt a false economy (and against the instructions of the finishing paint).

[thebraketester]

Mist coat always.

[Danm1les]

We have always used something like this: https://www.screwfix.com/p/fortress-trade-10ltr-br...

Works really well we have found.

[ARHarh]

Previous owner of my house did not do a mist coat when painting fresh plaster, the paint came off in big sheets. Took ages to sort out. I then used a mist coat (50/50 cheap emulsion with water) and its been fine for 12 years and a few coats of paint.

[billbring]

After a bad experience in a shower room, I did a bit of research and discovered Zinnser Guardz.
It's good stuff and not had any issues since redoing the room with this as a base coat.

I'd use it all on bare plaster now just to give the best possible chance of not having any issues.

https://www.brewers.co.uk/product/BN6022N

[dhutch]

JoshSm said:

I
Even if a mist coat was unnecessary it's not like a lot of time or effort is involved in doing it.

This.

I have seen vinyl based emulsion peel off plaster enough to never want to take the risk.

McPherson's Eclipse is good, as is Dulux Trade supermatt.

[OutInTheShed]

billbring said:

After a bad experience in a shower room, I did a bit of research and discovered Zinnser Guardz.
It's good stuff and not had any issues since redoing the room with this as a base coat.

I'd use it all on bare plaster now just to give the best possible chance of not having any issues.

https://www.brewers.co.uk/product/BN6022N

I was wondering how long before someone suggested a Zinsser product instead of a mist coat!

Sometimes PVA can be a good idea, like when a wall has been patched with filler.
I've never had an issue with vinyl paint bonding to a PVA'd surface, I think maybe that would happen if you slathered on undiluted PVA and got a shiny surface?

PVA is a water based vinyl polymer, just like vinyl paint....

[richhead]

If the top coat is matt then it most likely would be fine without, but for the sake of a partly diluted undercoat( i never go 50:50, more like 60:40) its worth doing. And you will probably find only the two coats are needed, and you often find you need to do two coats anyway.
However it the top coat is vinyl then it definitely will help it stick, but still use a mat for the undercoat, Do people still use vinyl?
Not a pro but 50 years of decorating.
Oh and with fresh plaster, leave it bare to dry properly, normally a week at least.

[Chumley.mouse]

Fresh plaster here just gets a quick going over ( mist) and then left to dry properly, i prefer to do more thin coats , never bad any issues.
Did try watering it down once and just found you get a lot more splatter and it drips more …..just seems a bit of a faff.

[Aluminati]

Your mate is correct. Size it then paint it.

[OutInTheShed]

richhead said:

....., Do people still use vinyl?
...t.

I think most 'standard emulsion' is vinyl based?

Or is the chalky st from 'name and other name' 'standard' now?