BCT 122
Roof Framing 1
Common Rafters Classroom Exercise
Lab project #1: Calculate the dimension lengths for assembly of the following:
2 x 6 rafters @ 24 inches on/center, 2 x 8 ridge , bird/frieze blocks, 2 x 6 fascia board,
barge rafters and gable end studs @ 16 inches on/center. 2 x 6 ceiling joists @ 24 inches
o/c spliced on the center bearing wall.
Building Span = 8 feet. Building length = 10 feet. Unit rise = 7 inches.
Birds mouth seat cut = 3 ½ inches. Rake overhang (barge rafter) = 12 inches.
Tail overhang = 8 inches.
Unit run = _________ inches.
Total number of common rafters = ___________________
Total number of barge rafters = ___________________
Unit line length = __________________
Unit line length factor = _____________
Unit rise factor = _______________
Rafter plumb cut = ______________ inches.
HAP = _________________ inches.
Rafter total line length. ( no overhang) ridge center to birds mouth =________________
Rafter tail line length. = _________________. Combined total length = _____________
Amount to shorten rafter for ridge = _______________
Assume ridge = 7 ½ inches net.
Length of king post from T.O.P to the bottom of the ridge = __________________
Amount each gable end stud will increase from short to long = +__________________
Amount to drop fascia board (assume ½ cdx ply sheathing) = __________________
Review wall plate and ridge layout.