Painting external concrete windowsills.

[needawin]

I have stripped my badly flaking window sills. Some are down to the bare concrete. Do I paint with ordinary undercoat and then gloss or should I be using a different paint?
Same topic. A lot of my radiators are flaking badly at the top despite the fact they are only a couple of years old. I have painted them a couple of times but they seem to flake again in the same places despite having rubbed them down well.

[The Builder]

I would guess that both problems are down to primers. A primer is, in a way, the most important of the paint layers.
If you're down to bare concrete over all of the sill, I'd go for a masonry paint such as Weathershield. If you still have old gloss on the sill, then you might be better off going with gloss again. Prime the bare sections with a good primer/sealer, or even a strong Water:PVA mix.

Same for the rads really. Loads of people have no trouble with ordinary gloss on a rad. Rub down with a wire wheel on a drill........... to bare metal. Use a universal, or a good metal primer......... then u/c and gloss.

[marden40]

as always, good advice from TB.......are you regularly drying clothes on the rads as you say its at the top......standard rads are not really designed these days to be painted over especially if they are only a couple of years old........don't get me wrong, its not a problem if you do paint them, but as stated, its all down to the preparation and coats.

[needawin]

Thanks both.