If you start your roof with a pair of commons fitted against the wall as illustrated in Sonnypaul's drawing then your dim's and hipped roof will work perfectly. The pair of commons effectively reduce the going by 50mm.I know your sick and tired of me lol but what you sketched is what I couldn't understand, my run is 1150 from inside of rafter to the corner.
And then 1150 form corner to the centre of the middle rafter? The measurements wont be the same, I.e square
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