On 04/08/2020 11:10:13, 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?

On a very similar wooden structure I used 2 8x4 sheets of buffalo board.
No felt, apart from a strip on the apex. Slightly more expensive that
OSB and felt but much easier and will last longer.