Jim Alexander wrote:
"fred" wrote in message ...
In article , Tanner-'op
writes
George (dicegeorge) wrote:
There are lots of slipped slates on my roof, with rusty nails,
the local builder recommends reslating the whole roof
rather than patching it again and again.

A good decision.

At the moment there is no felt, he advises felt,
is there any reason not to use felt?

There is every reason to *USE* felt. The main one is that if a
slate slips
or breaks then the felt (if properly fitted) will prevent water from
entering the roof space until the slate can be replaced.

Totally agree, a failsafe (faildry?) system has to be better than one
which allows damp ingress on a single point of failure.

Except a single point of failure (a single slate slipping) does not
result in a leak unless the slate below is also faulty.

Well that's what the felt is there for - just in case more than one slate
breaks or slips!

Anyway I fail to understand the reliance on a material with a much
lesser life than the 100 years plus of 2 layers of slate.

Slate is a rather brittle material, especially if a ridge tile blows off and
bounces down the roof or, frost gets into a small crack and does it 'dirty
work' over a period of time!

OK there are now better materials than traditional felt.

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

Tanner-'op