Identification. Load-bearing dimension lumber for studs, plates and headers shall be identified by a grade mark of a lumber grading or an approved inspection agency. Studs shall be a minimum No. 3, standard or stud grade lumber.

Bearing studs. Where joists, trusses or rafters are spaced more than 16 inches on center and the bearing

studs below are spaced 24 inches on center, such members shall bear within 5 inches of the studs beneath.

Exceptions:

1. The top plates are two 2-inch by 6-inch or two 3-inch by 4-inch members.
2. A third top plate is installed.
3. Solid blocking equal in size to the studs is installed to reinforce the double top plate.

For illustrations; [Click Here]

Top plate. Wood stud walls shall be capped with a double top plate installed to provide overlapping at corners and intersections with bearing partitions. End joints in top plates shall be offset at least 24 inches.

Bottom (sole) plate. Studs shall have full bearing on a nominal 2 by or larger plate or sill having a width at least equal to the width of the studs.

Interior load-bearing walls. Interior load-bearing walls shall be constructed, framed and fireblocked as specified for exterior walls.

Interior nonbearing walls. Interior nonbearing walls shall be permitted to be constructed with 2-inch-by-3-inch studs spaced 24 inches on center or, when not part of a braced wall line, 2-inch-by-4-inch flat studs spaced at 16 inches on center. Interior nonbearing walls shall be capped with at least a single top plate. Interior nonbearing walls shall be fireblocked.

Drilling and notching of walls– For information and illustrations on drilling and notching; [Click Here]

Fireblocking. Fireblocking shall be provided to cut off all concealed draft openings (both vertical and horizontal) and to form an effective fire barrier between stories, and between a top story and the roof space.