On 12/05/2021 18:57, Chris Bacon wrote:
This flaming garage pent roof is giving me a headache. It's a 6m deep,
5m wide building.

I have found that I can't use 3" (sinusoidal) corrugated iron, 'cos the
height peak to peak of the stuff is only 19mm, and I've a 6m run, and it
is likely (!) to leak, 'cos it needs a minimum 10° slope, and I've only
got ~4.4. So it's got to be 34/1000 box profile, which is said to be OK
down to 4°.

There are still disadvantages from my perspective, but I think I can
live with them.

One thing I can't have, though, is the 5m wide front of the thing
looking like castle rampartd in miniature, so it needs some sort of
flashing to get over that.

What's used for this? Barge boards, yes, for the sides, which are like
sheet metal equal angle, but what about the ends? Surely if I just use
barge board, the 90° angle will be wrong, and it will allow water to
blow up the tiny slope, and run back under the roof sheets, which is not
what is wanted!

90° barge flashing should be fine. It flexes a bit, so should fit over
the high end with no problem - with sealant at the join or closed cell
foam strips pushed in, to stop rain blowing up and over the end behind
the flashing.

At the low end, sit it on the roof sheets, but set it back an inch - so
that the ends of the sheets are an inch back from the vertical of the
flashing and can drain to the gutter below, but are hidden.

In my case, I haven't done that, but with a low angle, I siliconed and
rivetted 10mm aluminium angle along the end of the bottom of the sheets,
as otherwise I found that water stuck, turned under and was blown along
the underside of the roof sheets, causing damp.