Painting an exterior wall - need some paint advice please

GustyGardenGalaxy

I need to paint an exterior wall of a building, preferably tomorrow and Saturday when the weather is supposed to be dry (hah!).

The (concrete rendered) wall has had a few coats of white paint over the years, and quite a bit was flaking off. I've scraped off anything loose or bubbling AND treated it with algae/fungus remover as it was all rather green. That's now removed and the wall is white again.

I understand that an oil-based paint is best and also, given that some of the remaining paint is slightly powdery (ie some of it leaves a white powdered residue on your fingers) I guess I should also use an oil-based sealer?

Is there a paint that seals and covers 'all in one go' (or two coats) or should I use a separate sealer?

Whichever, can anyone recommend any makes please?

If it's relevant, I intend to use a roller to apply the paint.

Thanks

ormus

only use oil based paint if its been used previously. (and you may need an undercoat).

masonry paint is normally water based, such as sandtex etc...

GustyGardenGalaxy

I'm not sure what's been used before to be honest.

So how about sealing the old paint given that it's powdery in places?

Thanks

MX5huggy

You don't need to seal it. Just use a quality masonry paint.

ormus

use a jet wash and maybe a wire brush to remove any loose stuff etc....

GustyGardenGalaxy

Thanks for the advice.