In message , tony green
writes

"Dave" wrote in message
...
Some recent extension work involved slightly changing the run-off point
from a section of flat roofing. Where the new felt at the run-off point
was bonded to the old felt there's now a ridge (about 5mm) so an area of

When I started work in the roofing trade in 1954, all felt roofs had the
outlet standing up about 1"or 25 mm to retain a wet surface,

Which is ok until a leak somewhere occurs...

then came the
idea of lime stone chipping and now theve gone back to just plain mineral
felt as in the 50s. Flat roofing felt as change over the last 50 years so a
drop os water wont hurt only in your dislike of seeing it there.

hmm, very much a case of it depends I think.

We used to have a fair amount of standing water on our flat roof. The
roof was surrounded by a low parapet wall and the felt went up onto
this.

This was always a weak point IMO where the felt bent upwards. The joints
would gradually open. In winter the water would lie for months against
this bit of the roof, freezing and melting, leaking through the rof here
was pretty much a certainty.

We solved it when the roof was redone, by levelling out the roof a bit,
and by putting in a sort of 'gutter' at one side of the roof.
--
Chris French, Leeds