Tempo:
are supported on top of load-bearing walls or intermediate beams (Figure 53), or framed into the side of the beam (Figure 54). When a load-bearing wall runs parallel to the joists, it must be supported by a beam or load-bearing wall in the basement. Floor designs often require a load-bearing wall located at right angles to the floor joists, but offset from the joist support. Load-bearing interior walls at right angles to floor joists should be located not more than 900 mm (36 in.) from the joist support when the wall does not support a floor, and not more than 600 mm (24 in.) from the joist support when the wall supports one or more floors, unless the joist size is designed to support such concentrated loads. Non-load-bearing partitions parallel to the joists should bear on joists or on blocking between the joists. The blocking should be 38 × 89 mm (2 × 4 in. nominal) lumber spaced 1.2 m (4 ft.) or less on centre.
When framing for large openings such as stairwells or fireplaces, the trimmer joists must be doubled if they support header joists (joists into which other joists are framed) more than 800 mm (32 in.) long. Header joists longer than 1.2 m (4 ft.) must also be doubled. Where unusually large openings occur, trimmer joists that support header joists more than 2 m (6 ft. 6 in.) long and header joists that are more than 3.2 m (10 ft. 6 in.) long must be designed according to accepted engineering practice. Nailing and assembly methods generally used in the framing of floor openings are shown in Figure 64. Joist hangers are often used to support long joist headers and tail joists. Joist twisting can be reduced and load sharing between joists improved by cross bridging, blocking, strapping or a ceiling finish fastened to the underside of the joists. Where a ceiling
64 Framing for floor openings where double headers and double trimmers are used first header second header first trimmer joist
length of opening
second trimmer joist
first trimmer nailed to first header first header nailed to tail joists second header nailed to first header first trimmer nailed to second header second trimmer nailed to first trimmer joist hangers may be required as an alternative to end nailing tail joists tail joist
When framing for large openings such as stairwells or fireplaces, the trimmer joists must be doubled if they support header joists (joists into which other joists are framed) more than 800 mm (32 in.) long. Header joists longer than 1.2 m (4 ft.) must also be doubled. Where unusually large openings occur, trimmer joists that support header joists more than 2 m (6 ft. 6 in.) long and header joists that are more than 3.2 m (10 ft. 6 in.) long must be designed according to accepted engineering practice. Nailing and assembly methods generally used in the framing of floor openings are shown in Figure 64. Joist hangers are often used to support long joist headers and tail joists. Joist twisting can be reduced and load sharing between joists improved by cross bridging, blocking, strapping or a ceiling finish fastened to the underside of the joists. Where a ceiling
64 Framing for floor openings where double headers and double trimmers are used first header second header first trimmer joist
length of opening
second trimmer joist
first trimmer nailed to first header first header nailed to tail joists second header nailed to first header first trimmer nailed to second header second trimmer nailed to first trimmer joist hangers may be required as an alternative to end nailing tail joists tail joist
©
2026
Lehal.net