Phil L wrote:

Polystyrene? it doesn't soak up water at all, fibreglass does, but only the
stuff you would see in your loft, not the treated stuff used for CWI.

Water runs down the inside of your exterior brick/stonework during heavy
rain...if you could take down the inner leaf and look at the stonework
during a rainstorm you would see a mini waterfall! - this is normal and the
cavity stops anything getting to the inner leaf, this is why brick ties have
a twist or a bump in the centre, to allow water to drain down the cavity.


I've done a diagram and put it up on tinypic:

http://tinypic.com/view/?pic=rw5uyq

ty, I get it. I presume some walls do get running water, some dont. Now
I see why ratbond should also not be cwi'ed


NT