Reading the instructions for the above re. preparation, a coat of Sandtex Stabilising Solution is recommended to seal the surface before application of the masonry paint itself.
Works OK, but the stabilising solution itself appears, superficially at least, to be no more than a thin PVA solution. Does anyone know whether this is, in fact, the case, or is it a more complex product than that?
PVA would certainly be cheaper, but I'm not looking for false economies. .
I'd say the stabiliser is probably an unpigmented version of the paint itself, so more likely to be an acrylic. Could also be more penetrative than pva
One way to find out what is in things is to look up the COSHH datsheet on the product. The manufacturers web site should have them available for download.
I was under the impression that you only needed to use the stabiliser if the surface was powdery, ie rub your fingers along it and they get covered in fine dust. I didn't use stabilser last year on our walls, combination of pressure washed stone or painted render also pressure washed to remove the loose paint. Did use a slightly diluted first coat then two full strength, it has survived the winter...
I think a point needs making here. 'sealers' is a generic term, and in this context there are two entirely different classes of product that do two entirely different things. The binders, and the waterproof coatings
As far as the binders go, I find most professional painters simply use a coat of thinned paint. Its shade more expensive, but it has got SOME pigment in, and if a piss coat plus two coats rather than 3 coats overall plus sealer is what it takes to get the color depth, its overall cheaper probably.
Whilst paint or sealer does slow water uptake, it also slows water egress, That means a painted sealed render is not that much better tan a panted or indeed a bare render at frost attack.
And it can breathe and dry itself out.
If you go the weathershield or whatever route which puts an impermeable layer in on the render surface, you will indeed completely stop water getting in, but you may also stop it getting out if it gets behind the sealed render surface.
My approach is to use the latter sparingly in places that are both cold and subject to high water splash, ONLY where spallation has been established as happening anyway. In my case that's the tops of lead covered drip boards over the windows, on the house North side.
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