Can anyone advise how to paint over old paint? (PIGLET JOHN klaxon)

[ReallyNotAMorningPerson]

We replastered a corner of our bathroom last December and painted over it (Little Greene Intelligent Emulsion). The paint started peeling off about 3 months later. I don't know if it's because we put it onto new plaster (it had dried about a week though).

Being dunces, we flaked off the peeling off bits without sanding down the surrounding areas and just repainted it - so it just looks awful now!

I'd like to have a go at sanding it down and starting again. But could anyone advise me how to go about it?

Do I sand down the whole section of wall, or just the bits around the troublesome areas? And how do you sand? I just want the wall to look smooth again. I've tried to youtube it but not found anything yet.

How the paint looked flaked off

How it looked once we repainted over it (without sanding).

You need to get some medium to fine grade sand paper and sand off all the flakes lightly until they have gone. Don't go mad sanding as, if you do, the plaster goes weird and shiny

If I had to repaint an area that size, I'd do the whole wall with a roller (avoid brush marks then) as I find it really hard to match in the areas.

Piglet John may have better technical advice though!

Did you do mist (diluted) coats on the plaster before the proper/undiluted coats?

Plain no we didn't. We just put a primer on, then the Little Greene afterwards.

Once the plaster is exposed after sanding, should I do a diluted coat first?

Gobbolin thank you. The total area affected (though only patches of the area) looks like this. Should I sand off the whole area (about 1.5m x 0.76m) or just the bits that are flaky?

I would do diluted coats (prob 3) until the plaster stops absorbing the paint. I tend to use Dulux trade supermatt for the mist coats then paint with the (more) expensive paint in top of that. I. Usually do one coat that is 50:50, one that is 70:30, and one 90:10, but PigletJohn will probably tell you what is best. New plaster drinks up the paint and it kind of disappears into the plaster so you can barely see it, particularly the first coat.

I would sand off the while area (carefully).

I think primer is frowned upon these days.

Whole not while

Thanks Plain that's helpful. Could I ask one more question - how much time would you leave for the whole process (just roughly)?

I don't know exactly how long you should leave. My decorating is always done when the Dcs are at school so short bursts each day rather than long stretches. I would certainly leave the min time on the side of the paint tin before doing another coat. It would be a shame to rush it and end up with a poor result.

Great thanks Plain that's been really helpful.

I was asking about mist coating the other day. You only need to do one diluted paint mist coat. Follow the instructions on the paint tin as to the drying time between coats.

Thanks wow - does anyone know how long it might take to sand off that whole area? (1.5m x 0.75m approx)

N.B. We're on a bit of a tight deadline in case anyone wondering re. my obsession with how long things might take.

Sanding shouldn't take long at all. Good luck!

Hooray - that's good news! Thanks Plain

you might try a broad metal scraper rather then sandpaper, held almost flat to the wall. It is better at getting paint and snots off without roughening the polished plaster surface.

To fill small blemishes in plaster, mix half a cup of finish plaster or board joint plaster to the consistency of custard, and press it into the wall with a broad filling knife. Press hard enough, and apply so little, that you can see through it except where it has filled a blemish. You need about a twentieth of the amount you think. You will have to practice.

There is no point in applying extra plaster or filler that you have to scrape off afterwards.

p.s.

What was the primer you used? Not glue, I hope?

Agree with piglet John.

Use a broad base scraper to go our the corner first, to get as much of the flaky stuff off as possible. Then use a medium grade sandpaper to make it as smooth as you can. Fill any holes, then use a really fine grade sandpaper to get a really good finish.

Rub with a cloth to get the dust off. I use a vacuum cleaner brush, then a cloth.

Then water down - at least 50/50 some emulsion - not vinyl or silk , the plaster should just soak this up.

Give it a coat, then about 2 hours later another coat. Then you can top coat it. The plaster needs to be able to dry out slowly over time, so you need to use a paint which will let the wall 'breathe'.

Thanks PigletJohn - it was just a plain no-frills primer from B&Q.

Someone suggested PVA glue to me to make the plaster adhere this time...is that a definite no-no?

Snow - thanks. Does that mean bathroom paint is also a no-no? (It's for a bathroom)

Sorry Piglet - re. 'board joint plaster' - is this the kind of thing you mean:

www.wickes.co.uk/Wickes-Ready-Mixed-Jointing-Compound-10kg/p/220995

Or this:

www.diy.com/departments/gyproc-easi-filler-1kg/314800_BQ.prd

jointing compound, though Easifill would do.

It looks like I can see the bare plaster showing where the paint has peeled off, so whatever you used did not adhere. Bare plaster is usually "primed" with a mist coat or two of matt emulsion thinned with water. On new, wet plaster that is still drying out, you use a non-vinyl such as Supermatt, because it is porous and the moisture can escape, but it is not very durable.

The are very few people left who advocate using PVA glue. Most of them have been killed by angry decorators who have unsuccessfully attempted to paint it.

Thanks Piglet (sorry for slow replies) dodgy internet where I am today.

Definitely won't be using glue then!

Can I just clarify that once I sand down to bare plaster, I then do this mist coat with watered down emulsion (to seal), and then apply the joint compound on top of that?

(Last Q - I promise )

I'd use the easy fill. I always mix the filler slightly softer than ready mixed.

Filler first, then mist coat.