On Apr 3, 9:27*am, fred wrote:
In article et, Dave
Liquorice writesOn Fri, 03 Apr 2009 01:14:27 +0100, Tim S wrote:

As I understand it, sarking is for windproofing, not water proofing a
tiled roof?

No it's secondary waterproofing to guard against broken/slipped tiles or
heavy rain/wind blowing water in between the tiles. Don't under estimate
the power of the wind to blow water up hill...

Well put.

When putting celotex between rafters it is even more important to
exclude water. If it creeps into the unventilated trough formed by the
celotex, between the rafters, it wont be able to escape and we all know
where that leads.

The point is that you simply don't do it without arranging adequate
ventilation. It's not all about letting water ingress from outside
escape.

MBQ