Tempo:
(see Figure 90). A 19 mm (3⁄4 in. nominal) nailing strip is fastened to the rafter located above the gable end wall. Blocking spaced at 600 mm (24 in.) on centre is used to support the soffit covering. This blocking is toenailed to the nailing strip and end-nailed to the rake rafter. The soffit covering is then installed and nailed to these supports and a fascia board is added.
Low-Slope Roofs
Gable-end projections extending more than 300 mm (12 in.) beyond the wall should be supported by framing members called “lookouts” (see Figure 89). Gable-end studs are placed with the narrow face parallel to the sheathing, and a top wall plate is added. The lookout members, usually the same size as the rafters, are spaced at 600 mm (24 in.) on centre.
Where rafters also serve as ceiling joists, the term “roof joist” is used. Their size is determined by both roof and ceiling loads. (See Tables 29 and 30 on pp. 295-297) Rafters chosen for structural adequacy may not, however, provide adequate depth for insulation and ventilation of the roof space. In such cases, wider lumber or engineered wood products should be used.
The ends are supported by end-nailing to the first rafter and inboard of the gable end to the top plate of the gable. Blocking is then fitted between the lookouts in line with the wall line to support the roof sheathing and inner edge of the soffit covering. The soffit covering is nailed to these supports, and a fascia is added. The length of lookout members should be at least twice the width of the roof overhang. A double rafter is used to support the inner ends of the lookout members when they project into the roof more than one-and-one-half rafter spaces.
Roof joists for low-slope roofs are usually laid level or nearly level, with roof sheathing and a roof covering on top. The underside of the roof joists supports the ceiling. A slope of at least 1:50 is required for drainage. Slope the joists by adding a ledger strip at the top of the bearing wall or by adding a tapered strip to the top of the joists.
Low-slope roofs must be constructed more water-tight than pitched roofs because drainage is poorer. They sometimes support decks or terraces or occasional traffic and therefore must be protected with durable, wear-resistant materials.
Lookout rafters are usually used when an overhang is provided for a low-slope roof (Figure 91). If the lookout rafters project into
91 Typical construction of a low-slope roof with overhang alternative framing layout (dashed lines) roof joist lookout rafter header
exterior wall plate rafter header
Low-Slope Roofs
Gable-end projections extending more than 300 mm (12 in.) beyond the wall should be supported by framing members called “lookouts” (see Figure 89). Gable-end studs are placed with the narrow face parallel to the sheathing, and a top wall plate is added. The lookout members, usually the same size as the rafters, are spaced at 600 mm (24 in.) on centre.
Where rafters also serve as ceiling joists, the term “roof joist” is used. Their size is determined by both roof and ceiling loads. (See Tables 29 and 30 on pp. 295-297) Rafters chosen for structural adequacy may not, however, provide adequate depth for insulation and ventilation of the roof space. In such cases, wider lumber or engineered wood products should be used.
The ends are supported by end-nailing to the first rafter and inboard of the gable end to the top plate of the gable. Blocking is then fitted between the lookouts in line with the wall line to support the roof sheathing and inner edge of the soffit covering. The soffit covering is nailed to these supports, and a fascia is added. The length of lookout members should be at least twice the width of the roof overhang. A double rafter is used to support the inner ends of the lookout members when they project into the roof more than one-and-one-half rafter spaces.
Roof joists for low-slope roofs are usually laid level or nearly level, with roof sheathing and a roof covering on top. The underside of the roof joists supports the ceiling. A slope of at least 1:50 is required for drainage. Slope the joists by adding a ledger strip at the top of the bearing wall or by adding a tapered strip to the top of the joists.
Low-slope roofs must be constructed more water-tight than pitched roofs because drainage is poorer. They sometimes support decks or terraces or occasional traffic and therefore must be protected with durable, wear-resistant materials.
Lookout rafters are usually used when an overhang is provided for a low-slope roof (Figure 91). If the lookout rafters project into
91 Typical construction of a low-slope roof with overhang alternative framing layout (dashed lines) roof joist lookout rafter header
exterior wall plate rafter header
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