Building Construction Flashcards
Book 29 Building Construction
Roof Styles
Gable Hip Flat Bridge Truss Arch Sawtooth
Book 29 Building Construction
Gable Roof
Conventional
“A” Frame configuration
Rafters: 2x6” or larger
16-24” on center; 36” for steep pitch
Ridge: 1x6” ridge board or none if 2x6” rafters butted together
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Gable Roof
Lightweight
2x3” or 2x4” wood trusses held together by metal gusset plates
Top chord (compression), Bottom chord (tension), Webbing
18G, 3/8” penetration
Truss rafters 24” on center
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Roof Truss Clips
Nailed to bottom chord (every 3-5 trusses) and top plate of interior walls.
Provide stability for interior partition walls
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Hip Roof
Conventional
Ridge board, hip, valley, jack, and common rafters
Ridge 2x6” or larger
Rafters 16-24” on center
36” rough cut on older structures with steep pitched
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Bridge Truss
30s and 40s Truss members 2x12" Tie rods vertically for additional support Rafters 2x6 or larger 1x6 sheathing Plywood over existing if modified for EQ
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Bowstring Arch
30s, 40s, and 50s small and large commercials 2x12 or 2x14" lumber rafters 2x6" sheathing 1x6" plywood over existing if modified for EQ
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Lamella Arch
Egg crate, geometric, or diamond patterned roof
2x12” wood framing with steel plates and bolts
sheathing 1x6”
supported by exterior buttresses or internal tie rods with turnbuckles
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Lamella Arch
Hazards
Total roof collapse may occur if fire removes more than 20% of roof structure
Domino effect
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Tied Truss Arch
Similar to bowstring and lamella
uses metal tie rods to offer lateral support for the walls
Tie rods 5/8” with turnbuckles ensure arches do not push exterior walls outward
Top chords =laminated 2x12” or larger
Rafters 2x10” or larger
1x6” sheathing
Plywood over existing if modified for EQ
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Sawtooth
Commercial buildings to yield additional light and ventilation for manufacturing type occupancies
Rafters 2x8” or larger
wood and/or metal supports for bracing
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Conventional Flat
Rafters 2x6” or larger laid across outside walls
Sheathing 1x6 or plywood (3/8 to 5/8”)
Comp
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Wooden I Beam
Top(compression) and bottom(tension) parallel wooden chords connected by wooden stem
2x4” and 2x3” chords low grade of lumber
Stem 3/8” plywood or chip board
Connected by continuous glued-edge joint
Either top or bottom chord supported to wall
24” on center spacing
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Nailing Block
Perpendicular to top chords
4’ apart
Provides additional nailing surface for 4x8’ plywood
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Diaphragm Nailing
For nailing plywood
8’ crosses structural members
4’ parallel to structural members
staggered every 4’
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Open Web Roof
Top and bottom parallel wooden chords cross connected by steel tube web members
Top chord is supported; bottom chord unsupported
Chords either laid on edge or flat
Steel tube web members 1-2” cold rolled steel with ends pressed flat into a semicircular shape with hole punched through end
Flat ends inserted into slots in the chords and up to 1” steel pins driven through
Spans of 70’ of 2x3s and 2x4s by joining different lengths in glued, mitered “finger joints”