Exterior windowsills

OK, painters, what should I be doing in order to make the paint stay on window sills? It keeps flaking off, right back to the first day paint. The last time it was done I had painters do it, but they are as bad as ever. Tips please.

mike65

I did mine last summer, first I layed down the law with stripper then lightly sanded the concrete then I cleaned it with spirits. Then I applied a combined primer/undercoat- two coats worth. Following 24 hrs to dry off fully I applied two coats of concrete top coat.

Mike.

I'll try that this time round. Thanks.

Wertz

Paint falling off? Sounds like a problem either with the substrate (pre-cast concrete? stone?) or else that exterior emulsion has been applied to an underlying coat(s) of oil based gloss; is the "falling off" going back to bare substrate or to a previous coating?
If it's going back to bare then you have a problem either with water getting behind the paint layers or simply with adhesion, due to mould or a chalky surface. Pre cast concrete needs to be sealed with a special primer. I'm not so sure about natuarl stone (it's not something that's usually painted although it may have been on very old houses).

Mike's suggestion is a good one, but if you want to avoid messy stripping, just get some low grade sandpaper and take the paint back to a sound surface then apply a coat of oil undercoat and then oil gloss (or an exterior eggshell if you prefer)...but if, as above, it's going back to bare substrate, then you need to use the sealer I mentioned.

It's the precast concrete windowsills. In some parts they are bare, and some gone back to previous bits of colours.

Wertz

Was talking with another guy about this today at work, he reckons that a product by Zinsser called Bullseye primer is suitable for overcoating pre-cast crete without a need for a porosity primer. The oil base version would probably be most suitable.
Take the sills back as far as they will go with a scraper and sandpaper, until you get a sound surface, then use some of this bullseye (it comes in pint or litre size tins) to coat them up and apply your chosen finish (including masonry/exterior emulsion)
It should last 5 or more years without "falling off"...oil base will last longer but not everyone likes glossy windowsills...

Katzi

I had peeling concrete window sills too. I used a product called Owatrol E-B (which I got in the Decor Centre, Stillorgan). You get rid of all old paint first - or as much as possible. A wire brush did it for me. You mix Owatrol with your paint for the first coat, and then do a second coat with just paint alone. Very easy.

That was a year ago. My window sills are in full sun and exposed to lots of rain, wind etc. but still look great. Hope this helps.

iMax

Just a quick question on painting windowsills (sorry to hijack thread). Any opinions on a granite type effect ? We just had out walls & pillers replaced & the cappings used are granite effect & look really well. I was thinking of trying to emulate the same effect on the windowsills.

Wertz

Very tough to match in iMax...going to take an awful lot of trial and error. Not used much granite effect paints or speckle tones, but the means by which you build up the effect are through colours of basecoat then colours of the 2 (or more) speckle tone topcoats...getting the match exactly with natural stone is going to take time IMO. Get some of the sample cards for the product you intend to use then compare it side by side with the cappings in good light.

Katzi, yes EB is great stuff....just for anyone intent on using it, it's a paint plasticiser and can only be added to emulsions and exterior masonry paints NOT oil paints.

There's some great tips there, thanks folks. Maybe I should have mentioned that we are in a coastal area too. Anyway I'll try one of these and see how it goes.