It is well worth the effort to rough out the wall system to be square and level so the roof framing is simple.
How to level roof rafters.
While it isn t that difficult to build rafters the wall system supporting the roof must be level and square.
Mineral wool friction fits between rafters providing an optimum seal and preventing gaps associated with rigid foam boards which can otherwise lead to unwanted heat loss.
Use your string line to determine how much the roof need to go up.
Sagging rafters can lead to serious problems with the entire roofing system.
If needed shim trusses or rafters to level the nailing surface and install blocking to straighten any warped or bowed top chords of trusses or rafters.
In order to build rafters you need to know the roof pitch and the roof span overall width of roof.
If one support is as little as 1 4 inch lower or higher than the one next to it you might end up with an uneven roof.