Painting New Plaster

[jz5sjg]

Hi guys, hoping for some help.

I have had a pretty huge open plan area (50m2) plastered, half of it just skimmed, half scratch coated and plastered. Whilst putting the

2nd coat on the 1st (mist coat) is coming off on the roller.

- I let it dry out for approx 4 weeks and had an industrial dehumidifier in there for a week.

- When the plaster turned a nice light pink throughout, watered down some Wickes "trade" contract emulsion by 20-30% and gave it a miscoat.

- Let that dry for a few days, lightly sanded, then applied a 10% diluted coat of the same stuff.

However, on some walls the 1st coat is coming off in flakes and making a real mess of the wall. Any ideas what the common cause for this is please? Thought I had followed best practice!!!!

Thanks in advance SPC

[stevelup]

We've done eight rooms now and every time, the first coat was 100% Wickes trade magnolia and the second coat was the final paint colour. We've had no problems at all with the paint coming off and didn't do any of the watering down.

The biggest area was the kitchen (circa 35 square metres) and that only took three or four days to dry without any assistance before painting - I'm surprised yours took four weeks. The only thing we did was leave the windows on a vent position.

Steve

[Frank Erskine]

I suppose doing the first coat in magnolia is an incentive to get around to doing the top coat.

:-)

[Stuart Noble]

I've had this happen on occasions. The short answer is that the plaster has probably absorbed the liquid phase of the paint, including the added water, and left the pigment stranded on the surface with insufficient binder. Some paints are certainly better than others in this respect, and I've never had trouble with Crown emulsion straight from the tin.

I'd try not thinning the next coat. If it pulls the first coat off, just keep re-working it with the roller in the hope that the first coat will become absorbed in (and bound by) the second. Worked for me on a ceiling where I had my doubts about ever getting a decent finish

[stevelup]

Indeed!

[TheOldFellow]

Killfiled - used the M word. :)

I've just been through the same prcess with a large room with skimmed PB walls. I waited about 4 days for the skim (Thistle Board) to go pale pink, then did a coat of full strength B&Q super-cheap emulsion (I really enjoyed putting it on - excellent coverage), next day the top coat (Dulux Luxurious Silk). No problems whatsoever - although there is a lot of condensation in the loft on the sarking due to the very cold weather and the water used to mix.

It might be the plaster used. Are the walls with problems the PB ones, or the scratch coated?

R.

[The Medway Handyman]

Get some of the magic paint they use on DIY SOS. Can be applied to freshly platered walls, covers in one coat & drys in 15 mins :-)

[Mark]

Could be that the plaster has been 'polished'. Meaning that the plasterer has gone over it with his trowel several times to get a hard almost glassy surface.My plasterer does this. If you stand at an acute angle to it you can see reflections. I've been using B&Q white emulsion for 'New Plaster' which seems ok so far.

mark

[Mark]

I've often needed to dilute emulsion by 50% on new plaster. Otherwise the paint dries too quickly and flakes off.

M

[Ashnook.]

Will using diluted PVA first help? I am also interested in this problem.

[Mark]

I've heard it's a bad idea to use PVA for this. However I've never tried it myself.

M.