BCT 122 Roof Framing 1 Roof Framing Procedure
BCT 122 Roof Framing 1 Roof Framing Procedure Sequence
Wall Plate Check & Layout • Verify (measure) building span dimensions. • Check walls for straight and bracing. • Lay out plates for rafter and Joist O/C spacing.
Ceiling Joist • Ceiling joist parallel to rafters that make the entire span may fall to either side of the rafter and are nailed securely to the wall plate (3 – 8 d) and laterally into the rafter. (3 – 10 d) • If the ceiling joist does not span, it must be lapped a minimum 3” and nailed together. • Ceiling joist starting on opposite sides of the rafter require a block under the rafter to tie the rafters on the interior partition. • Joists may need to be clipped if they extend above the rafter. Remember Crown up!
Clip Joist Ends if Necessary
Calculating the Common Rafter • Using the Pythagorean theorem, calculate the hypotenuse of 12” unit run & the given rise. This is the unit line length. • Line length factor is the unit LL ÷ 12”. • The rise factor is the unit rise ÷ 12”. • The rafter length is unit LL x ½ the span. • The rafter tail length is overhang inches x LL factor. • The rafter shortened for a ridge board is ½ the ridge thickness x the LL factor or ½ the ridge thickness perpendicular to the plumb cut.