If the roof is not completely square you can decrease the space between joists but never increase the space.
How far apart are roof joists on 10x10 lean to.
Then use the circular saw to cut a 1 by 3 5 inches 2 5 cm 8 9 cm notch 10 25 inches 26 0 cm from the top of each rafter.
In other words you would space a roof joist 15 inches apart from another roof joist but never 17 inches apart.
But they do tend to space rafters in one of several industry standard increments.
430 cm long in order to cover the sloping roof and hang off of the far side.
You can simplify the construction of your lean to roof even more by building your own trusses.
Measure from the ends.
Rafter and roof joist spacing is only one part of a complex roof design that works together to form a structure that meets building codes and can hold up the weight of the roof and roof load.
A lean to roof also known as a shed roof is the simplest roofing design and the simplest to build because the roofing material usually covers only a single rectangular plane.
Frame the top side wall of the lean to roof with 2x4 lumber.