Tempo:
to the doubled joist. The spacing of these tail joists is usually the same as that of the main ceiling joists. Cut rafters to length with the proper angle at the ridge and notches (known as bird’s mouth joints) on the eaves. The heel or lower part of the rafters should bear directly over the exterior wall. Depending on the design of the roof and the shape of the outside walls, place the rafters:
directly on the wall plates (see Figure 83); on a rafter plate nailed to the top of the ceiling joists (see Figure 84); or on a load-bearing wall supported on the exterior wall plate (Figure 86).
The last method is used where a portion of the outside wall is inset. The ceiling joists extend beyond the exterior wall and are nailed to the side of the rafters. This provides lateral support for the bearing wall and stability for the ends of the rafters.
A ridge board (see Figure 83) or a ridge beam (see Figure 84) is used to ensure a level ridgeline and to facilitate placement of the rafters. Erect rafters in pairs and nail them to the ridge board or beam. Toe-nail the lower ends to the wall plate. Locate each pair of rafters directly opposite each other or offset at the ridge by not more than their thickness. Offsetting is required to maintain vertical alignment of the rafters when the lower ends are tied to ceiling joists that have been lapped (rather than butted together) at the centre load-bearing wall (see Figure 84). A roof that slopes less than 1:3 should be vertically supported at the peak. This can be accomplished by providing a 38 × 140 mm (2 × 6 in. nominal) ridge beam supported at 1.2 m (4 ft.) intervals by 38 × 89 mm (2 × 4 in. nominal) vertical struts (see Figure 84). A load-bearing wall may be used instead of the ridge beam. Since the ridge support does not result in outward thrust of the roof members, continuous ties between the lower ends of
86 Rafter heel supported on load-bearing wall ridge board intermediate struts to be set not less than 45º to the horizontal
studs in load-bearing wall located directly under each rafter 38 mm (2 in.) thick splice plate interior bearing wall roof rafters notched and bearing directly on top plate of exterior wall continuous nailer and soffit supports ceiling joists extend beyond the exterior wall and are nailed to the rafters and toe-nailed to the double wall plate wall sheathing
exterior wall
directly on the wall plates (see Figure 83); on a rafter plate nailed to the top of the ceiling joists (see Figure 84); or on a load-bearing wall supported on the exterior wall plate (Figure 86).
The last method is used where a portion of the outside wall is inset. The ceiling joists extend beyond the exterior wall and are nailed to the side of the rafters. This provides lateral support for the bearing wall and stability for the ends of the rafters.
A ridge board (see Figure 83) or a ridge beam (see Figure 84) is used to ensure a level ridgeline and to facilitate placement of the rafters. Erect rafters in pairs and nail them to the ridge board or beam. Toe-nail the lower ends to the wall plate. Locate each pair of rafters directly opposite each other or offset at the ridge by not more than their thickness. Offsetting is required to maintain vertical alignment of the rafters when the lower ends are tied to ceiling joists that have been lapped (rather than butted together) at the centre load-bearing wall (see Figure 84). A roof that slopes less than 1:3 should be vertically supported at the peak. This can be accomplished by providing a 38 × 140 mm (2 × 6 in. nominal) ridge beam supported at 1.2 m (4 ft.) intervals by 38 × 89 mm (2 × 4 in. nominal) vertical struts (see Figure 84). A load-bearing wall may be used instead of the ridge beam. Since the ridge support does not result in outward thrust of the roof members, continuous ties between the lower ends of
86 Rafter heel supported on load-bearing wall ridge board intermediate struts to be set not less than 45º to the horizontal
studs in load-bearing wall located directly under each rafter 38 mm (2 in.) thick splice plate interior bearing wall roof rafters notched and bearing directly on top plate of exterior wall continuous nailer and soffit supports ceiling joists extend beyond the exterior wall and are nailed to the rafters and toe-nailed to the double wall plate wall sheathing
exterior wall
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