On Mon, 28 Apr 2008 19:12:35 +0100, a particular chimpanzee,
"Tanner-'op" randomly hit the keyboard
and produced:

Jim Alexander wrote:

OK there are now better materials than traditional felt.

You have to use a 'permeable membrane' material now rather than the old
bituminous felt.

You don't "have to"; bituminous felt is still acceptable. I would go
for a breather membrane, though.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"