Painting on plaster

[Andrew Le Mas]

Following replastering of my wall I have waited five months for the wall to dry out. This will sound like a crazy amount of time but I have had a slight damp patch where the timber has been historically soaked with water ingress. The exterior brickwork was fixed prior to replastering but it could take years for the slight damp patch to leave.

I have also since realised that the skimming job has been substandard and there are some issues with it (as pictured).

My current plan is to apply a mist coat (zinsser/water mix) and then sand/fill to try and remove any imperfections the mist coat identifies. After that I am planning another mist coast followed by a coat of pure zinsser cover stain. Following that I intend to add 2 topcoats of normal paint. From more experienced painter/decorators is this overkill or necessary for a good finish?

 

[JohnD]

why zinsser?

 

[Andrew Le Mas]

I’ve been told it is good to block any damp staining coming through from the plasterwork

 

[JohnD]

but you want the wall to continue drying out.

it's not a stain, it's a damp patch. So you don't need a stain blocker.

Have you got a room fan or desk fan?

Put it blowing directly onto the damp patch. The moving air will evaporate away the water. You will notice the difference. You do not need a fan heater.

Paint the wall with Dulux Trade Supermatt (not a different paint with a similar looking name)

It is a non-vinyl paint that allows moisture to evaporate off through the porous surface.

Start with your mist and rectification of defects, finish with full coats. White is cheapest but you can get other colours mixed.

When you are satisfied that the wall is fully dry, you can use other paints or papers. Most other paints include vinyl or acrylic and are more durable, but do not allow drying out and may bubble or blister.

Other major paintmakers also offer non-vinyl porous paints, labelled "for new plaster" that say they allow drying out.

Warning:
Do not put glue on any surface that you hope one day to paint.

 

[Andrew Le Mas]

Thanks @JohnD for your very kind suggestions.

I am very inexperienced with painting so your recommendations are greatly valued.

I will mistcoat with the Dulux Trade Supermatt and then sand/fill and then add a second mistcoat layer before applying full coats.

Would a 60% paint / 40% water be suitable for the mistcoat?

Thanks again

 

[JohnD]

it will soak in well, but you will need a second mist coat with that much water. Try 80/20

the first will soak in and disappear, the second will not soak in so deep.

you can use as little as 10% water, but more gives better penetration.

Try Joint Cement or Easiplast for your fine filling, they are plaster products and better than filler.

If you have a fan, start using it straight away.