First coat of paint onto new render

[Martin Pentreath]

Hi all,

I need to paint a rendered extension with some Dulux Weathershield. What is the right proportion to water down the paint by for the initial coat?

Cheers!

Martin

[Rod]

The actual Dulux Weathershield usage guide to follow depends on which of the many Weathershield products you intend using. For example:

[Martin Pentreath]

Many thanks for the prompt reply Rod, and yes you're right, it says that on the tin! I'll go and sit in the corner ...

[Stuart Noble]

It's a bit like thinning custard. If you shake it enough you may get the illusion of a uniform consistency but the two phases, water and resin, are always separate. The water you've added soaks into the render, together with (depending on the porosity) essential solvents from the paint itself, making it difficult for a proper film to develop. I prefer to use a stabilising solution and then the paint straight from the tin

[mike]

Can you enlarge on a description of a stabilising solution please ?

[Stuart Noble]

Any proper paint outlet should stock it. This is the kind of thing, though it looks a little expensive for what it is

[Martin Pentreath]

Interestingly the Dulux Weathershield instructions expressly say:

"If the surface is still powdery after thorough preparation, seal it with a coat of Weathershield Stabilising Primer, but do not seal sound, new or bare surfaces."

[Stuart Noble]

Slightly ambiguous! Good old Dulux. It's really a question of how porous your new render is rather than how it looks or feels. I suppose if the stabiliser couldn't penetrate, and formed a clear film on the surface, you might have trouble getting the paint to cover well i.e. you'd see brush strokes, but I can't see that happening on normal render. Also, bear in mind that stabiliser is much more penetrative than water.

The problem with all water based paints is that they contain solvents which evaporate after the water phase so, although the paint is touch dry, they are still hanging around ensuring proper film formation. If they get sucked into the substrate, you tend to end up with a coating that looks fine but isn't continuous at a microscopic level.

[The Natural Philosopher]

a bit. Till its still got color, but is more opr less watery. IIRC we did it about 2 paint one water.

[The Natural Philosopher]

I did get frost damage where I get driving rain..bouncing off flat lintels over the windows etc. ..use a penetrating sealer on north and west exposed areas.