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Posted to uk.d-i-y
The Natural Philosopher
 
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Default Flaking and blistering masonry paint.

Chris Bacon wrote:
lavenders19 wrote:
Hi guys. i painted my window sills with sandtex masonry paint on my
window sills. Now it has flaked and just peeled off. Why is this? I
did paint over gloss, but should this have affected it?


It's probably because the sills are made of concrete (or stone) and
are damp to some slight extent. The moisture in the material will
blister the paint as it tries to escape. You might do better to
strip the sills entirely, and re-do with a "breathable" paint
(Sandtex ultra smooth, for instance).


Another good trick is to use a watershield type coating before painting.