The angles and length depend on BOTH span and roof pitch. You provided only span. What pitch do you want? i.e. 5:12, 7:12, 12:12. Specify pitch and you may get your answer.

If I have a 12'4" wide barn ( outside to outside measurement) what is the angle cut needed for the 4 boards and the length of each board to create the barn roof? Please give the length from longest edge of cut board.

Additional information about the Roof pitch is 24:12 for side and 4:12 for top of roof

Thanks

They suggest creating a full scale pattern on the barn deck........

http://www.taunton.com/finehomebuilding/pages/h00130.asp

when I built my new 16x20 shed, I first laid out the rafter patern on the floor and constructed the rafters as modified trusses. Then I framed and applied the siding with the ends laid on the floor. when applying the siding, I first laid it on the frame, snapped a chalk line for the cuts and therefore did not have to worry about the length of the siding. after the ends were erected, the side walls were constructed and rafters installed.

JMHO

Carl

you have now added another variable by having two pitches. you have to decide what one length is before you can solve the equation. best to draw yourself a scale drawing on paper. if you can't do it on paper to attain an understanding of it, you can never hope to build it with lumber.

Excellence is its own reward!