On Sun, 09 Apr 2006 15:40:57 GMT, "Cicero"
wrote:

I think you're safe with MDF. Wickes and other such places sell ready-made
window boards - 1" with bull nose and ready primed. They must have faith in
their product.

Exterior-grade MDF has been available for a quite a while - at least
fifteen years. I remember when it was first introduced, my Dad (who
works in the timber industry) had an un-painted/un-varnished piece which
he left out in the back garden for a couple of years by way of a test
and it suffered no ill effects, other than attracting a bit of surface
moss/mould.

I don't know what it's bonded with to make it weatherproof - probably
some variety of nasty chemical or other!
--
Chris Cowley