On Tue, 4 Aug 2020 20:21:12 +0100, newshound wrote:

On 04/08/2020 11:10, TimW wrote:
This is an ordinary timber garden shed 8' x 10' (2.4m x 3m), the roof is
felt on treated sw boards on 3x2 purlins, a central ridge and a shallow
pitch of maybe 15deg. Very standard cheap wooden shed. Over 20 yrs I
have refelted and half re felted and it's leaking again, and the soffit
boards are totally rotted. The rest of the shed is of no particular
quality, and a a bit wobbly.

I was thinking of covering the roof with something better, hoping to
extend its life and usefulness - what would be good? Onduline?
galvanised steel? plywood and a rubber type sheet? some kind of new
material?

TW

IIRC the cheapest long-lived thing per square foot are the thin steel
plastic coated box profile sheets, but you might have to bodge the
ridge. If the boards are not too bad you could probably fit the sheets
using sticks like **** type cartridge adhesive, and save messing around
with roofing nails or screws.

I have to replace a corruline/onduline pitched roof soon, I shall
probably board it first but have not decided whether to use metal or
corruline. I have come to the conclusion that it is *only* worth using
the corrugated bitumen boards with full boarding underneath. Mine lasted
20 years but a stables that I rent has only lasted 10, owing to sagging
and splitting between rafters and purlins.

Chap next door had his shed roof done with a corrugated sheet that looks
remarkably like the asbestos cement that it replaced. The roofer - he lives
about 150m up the road - reckoned that it'll last about 50 years; the old
roof was about 70 yo but 10 past it's 'best before' date.
I did mine with Onduline about 3 years ago; the lean-to next to it was done
with Onduline about 10 years ago - still OK but showing its age.
The manufacturer claims 15 years if 'maintained' which, so far as I can see,
is not leaving debris, especially moss, on it for too long.
Next time I'll use the corrugated cement board or whatever it is, although
15 years might see me out (or 15 weeks the way things are going atm!).
The pitch on these roofs is about 7 deg. so I used 2m sheets on a 3m roof,
giving nearly 2m overlap (the rest is on the eaves).
Harder material would allow more overhang and that would be better at
keeping rain off the timberwork.
The roofs are fully decked under the Onduline so local pooling isn't an
issue.
--
Peter.
The gods will stay away
whilst religions hold sway