Plastering/Decorating query!

nin9abadga · 1 Dec 2008 at 10:36

Atrox Moris said:
When I moved back home I ended up in a room that my older brother had painted for my mum. He'd plastered the paint straight onto bare plastered walls. It started to peel. And not in little flakes, I could tear huge strips off the wall like it was wallpaper. So the whole room had to be redone (stripping paint off the wall with a wallpaper jobby and no resistance is a very easy job to do). Next door neighbour told us to make a 50/50 mix of undercoat and water, stir it up well and give it a coat or two of that then put on the undiluted top coat. So far no peeling (after a couple months).

M0T said:
This is the correct (time consuming) way to do it.

The plaster sucks the moisture out of the paint which is why it flakes off, by putting the mist coat (water/paint mix) on you avoid this problem. Usually you would do a 50/50 coat then a 25/75 coat before applying the paint neat.

good advice (and very timely!)

we are in the process of decorating our hallway. in a similar way, the paint was peeling off in big strips so we had to take it all off. tried a number of ways but eventually steamed it all off all the way to the plaster underneath. we haven't started to paint it yet - still more paint to get rid of - but we're about to get going on it. we'll take this advice i reckon! thanks.

philjohn · 1 Dec 2008 at 11:32

M0T said:
Theres a huge debate about the use of PVA on plastered surfaces - some say use it others say don't. The consesus seems to be that it is fine in the short term (and a time saver) but likely to cause problems in the long term.

Exactly, PVA should only be used to "key" old surfaces you are about to plaster.

To the OP, don't go and paint it straight away, you'll need to do a couple of "mist coats" with some dulux trade matt watered way down (50/50 split is a good starting point).

mishima · 1 Dec 2008 at 12:06

The first coat that went on was obviously very patchy... but the second coat helped. I was going to leave just two coats on but decided to go with three. It looks great. I'm pleased with the results and the paint has now dried and has fixed nicely. Checked on it this morning.

M0T · 1 Dec 2008 at 12:25

Its not now that you'd have the problems, its a few years down the line. The issue becomes that even if you repaint in the future that very first layer isn't properly adhered so you will get problems with peeling.

Make sure if you mask anything on that wall you use ultra low tack tape - the stuff that almost feels like it isn't sticky at all or it'll pull all the paint off.

mishima · 1 Dec 2008 at 13:17

Even if I've used a good coat of PVA bonding on top of the plaster?

M0T · 1 Dec 2008 at 13:25

mishima said:
Even if I've used a good coat of PVA bonding on top of the plaster?

Edit for clarification:

PVA on plaster is useful for somethings - i.e. providing a base for tiles.

But if you are painting the surface you should apply 2 mist coats in order to prevent paint problems in the future.

Also if there is moisture left in the plaster the pva seals it and the plaster can't breathe so you can end up with cracks appearing later on.

a1ex2001 · 1 Dec 2008 at 13:45

Skywalker said:
Simple answer is NO , the dark bits are not dry or your mix was wrong , stick the heating on for a few days to make sure its dry . I would never seal with pva on the new plaster just on the underside . Do the mix that MOT said or you will waste good paint aswell

I would second that, my paint brush would have been nowhere near that wall it should all be the light pink colour when it's dry (at least every wall in my house was!) We gave all our plaster a couple of weeks (some was just a skim some was right back to the bricks) to fully dry just in case as I sure as hell don't ever want to have to do it again. When it was time for painting we got a giant tub of B&Q value whit emulsion and mixed it about 75-25 with water (Cheap paint is really watery anyway) gave it a couple of coats of that and then got on with the proper paint. I always try and do the prep work right as it makes the finish last longer and saves me from having to go back and do it again!

mishima · 1 Dec 2008 at 15:16

M0T said:
Edit for clarification:

PVA on plaster is useful for somethings - i.e. providing a base for tiles.

But if you are painting the surface you should apply 2 mist coats in order to prevent paint problems in the future.

Also if there is moisture left in the plaster the pva seals it and the plaster can't breathe so you can end up with cracks appearing later on.

Ok thats for that. Well, just have to wait and see then there's not a lot I can do now. Hopefully it was dry enough

leaskovski · 29 Dec 2008 at 15:56

Well, im just in the process of doing some painting after some repair plastering has been done around my door. The guy slapped on some PVA before he put the base layer of plaster down. After he finished smoothing off the top layer, he said put a 50/50 paint/water mix on before giving it a proper paint. I went down the local trade today to pick up some cheepo paint to mix with, however, instead, i picked up a small pot of 'dulux plaster sealer' as this was cheaper (I didnt need a massive tin).