fred wrote:
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.

or is there an even better option?

A close boarded roof with felt and slate (Welsh slate being the
best) but the cost will frighten you! :-)

I thought all slate roofs were close boarded but that's what living in
Scotlandshire does for your perceptions. If cost isn't an object and
you might insulate or convert the loft later then a breathable
membrane in place of felt would be a further improvement. Any
(unlikely) damp ingress below the membrane would have a chance of
escape in warmer weather, saving timbers from potential rot.

Fred,

No not all slate roofs are close boarded - that is usually reserved for the
'better' class of building and the 'normal' house these days (and in the
past) is simply trussed, felted, battened and tiled - using a permeable
(breathable) sraking felt as a matter of course.

Tanner-'op