Questions and Answers
On a site having expansive soil, roof drainage water shall discharge a minimum of _____ from the foundation walls or to an approved drainage system.
5 feet
Where the roof pitch is less than _____, the structural members that support rafters and ceiling joists shall be designed as beams.
3:12
The maximum spacing of collar ties shall be _____ on center.
4 feet
Ends of ceiling joists shall be lapped a minimum of _____ unless butted and toenailed to the supporting member.
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What is the maximum allowable span for SPF #2 ceiling joists, spaced 24 inches on center?
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What is the maximum span of 2-inch by 8-inch Hem-Fir #1 rafters spaced at 24 inches on center under a 50 psf ground snow load?
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Purlins shall be supported by braces having a maximum unbraced length of _____ and spaced at a maximum of _____ on center.
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The ends of a ceiling joist shall have a minimum of _____ bearing on wood and a minimum of _____ on metal.
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Notches in solid sawn lumber ceiling joists shall not be located in the middle _____ of the span and are limited in depth to _____ the depth of the joist.
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An opening in a wood framed roof system may be framed with a single header and single trimmer joists provided the header joist is located a maximum of _____ from the trimmer joist bearing.
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What is the maximum span without edge support for 15/32-inch wood structural panels with a span rating of 32/16?
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What is the maximum allowable rafter span for 800S162-54 50ksi steel rafters installed at 24 inches on center in a 110 mph wind speed area?
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Openings provided for roof ventilation shall have openings a minimum of _____ and a maximum of _____.
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A required attic access opening shall have a minimum rough opening size of _____.
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A net free cross-ventilating area of 1/300 is permitted for roof ventilation, provided a minimum _____ vapor barrier is installed on the warm-in-winter side of the ceiling.
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Fire-retardant-treated wood shall have a maximum listed flame spread index of _____ when used in roof construction.
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In the attachment of asphalt shingles, special methods are required where the roof slope of _____ is exceeded.
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Double underlayment is required for an asphalt shingle application where the roof has a slope of up to _____.
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In an asphalt shingle roof application, step flashing on a sidewall shall be a minimum of _____ inches high and _____ inches wide.
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Nails used to attach concrete roof tiles to the roof deck shall penetrate the deck a minimum of _____ or through the thickness of the deck.
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Where the cantilevered portion of a rafter is notched, a minimum of _____ inches of the member depth must remain.
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Where No. 2 wood shingles are installed on a roof having 5:12 pitch, the maximum weather exposure for 16-inch shingles shall be _____.
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For preservative-treated tapersawn shakes installed on a roof, the spacing between wood shakes shall be a minimum of _____ and a maximum of _____.
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For a wood shake roof system, sheet metal roof valley flashing shall extend a minimum of _____ from the centerline of the valley in each direction.
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A notch located in the end of a solid lumber ceiling joist shall have a maximum depth of _____.
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In the framing of an opening in ceiling construction, approved hangers are not required for the header joist to trimmer joist connections where the header joist span is a maximum of _____ feet.
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Where eave or cornice vents are installed, a minimum _____ air space shall be provided between the insulation and the roof sheathing at the vent location.
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Where the attic height is 30 inches or greater, an access opening is not required in attics of combustible construction where the attic space is a maximum of _____ square feet in area.
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Overflow scuppers utilized for secondary roof drainage shall have a minimum size _____ of the roof drain.
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A ridge board shall be a minimum of _____ -inch in nominal thickness and have a minimum depth equal to _____.
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What is the minimum total net free ventilating area required for a 1,500-square-foot attic space?
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Where an unvented conditioned attic assembly is utilized, the use of wood shakes on the roof would require a minimum continuous _____ -inch vented air space between the shakes and the roofing felt.
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Where required on an asphalt-shingled roof of 5:12 slope, an ice barrier shall extend from the lowest edges of the roof surfaces to a minimum of _____ inches inside the exterior wall line.
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Drip edges provided at eaves and gables of asphalt shingle roofs shall extend a minimum of _____ inch below the roof sheathing.
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Study Notes
Roof Drainage and Structure
- Roof drainage water must discharge at least 5 feet away from foundation walls, especially on sites with expansive soil (R801.3).
- Structural members supporting rafters and ceiling joists must be designed as beams if the roof pitch is less than 3:12 (R802.3).
Joists and Spans
- Maximum collar tie spacing is 4 feet on center (R802.3.1).
- Ceiling joists must have ends lapped at least 3 inches or butted and toenailed to supports (R802.3.2).
- The maximum allowable span for SPF #2 ceiling joists at 24 inches on center is 14 feet, 9 inches using 2x6 members (Table R802.4(1)).
- For a roof system with a 50 psf ground snow load and a dead load of 20 psf, Hem-Fir #1 rafters (2x8, spaced at 24 inches) can span a maximum of 9 feet, 10 inches (Table R802.5.1(4)).
Construction Specifications
- Purlins should have braces with a maximum unbraced length of 8 feet and spaced no more than 4 feet apart (R802.5.1).
- Ends of ceiling joists must bear 1.5 inches on wood and metal (R802.6).
- Notches in ceiling joists should not be in the middle 1/3 of the span and are limited to 1/6 of the joist depth (R802.7.1).
Roof Openings and Ventilation
- An opening in a wood framed roof requires a single header and minimum 3 feet from the trimmer joist bearing (R802.9).
- Using 15/32-inch wood structural panels with a span rating of 32/16, the maximum span without edge support is 28 inches (R803.3.3).
Rafter and Roof Specifications
- For a dwelling in a 110 mph wind speed and Exposure B, the maximum rafter span allowed for specified steel rafters is 14 feet, 8 inches (Table R804.3.2.1(1)).
- Eaves cannot exceed a horizontal projection of 24 inches in a steel-framed roof system (R804.3.2.1.1).
Ventilation Requirements
- Openings for roof ventilation must have an opening size between 1/16 inch and 1/4 inch when covered with corrosion-resistant screening (R806.1).
- Attic access openings must have a minimum rough opening size of 22 inches by 30 inches (R807.1).
- A net free cross-ventilation area of 1/300 is acceptable in Climate Zones 6, 7, and 8 with a minimum Class 1 or 2 vapor barrier (R806.2).
Fire Safety and Installation Practices
- Fire-retardant-treated wood in roof construction must have a flame spread index of 25 or less (R802.1.5).
- Asphalt shingles require special fastening if the roof slope exceeds 21 units vertical in 12 units horizontal (R905.2.6).
- Double underlayment is mandated for asphalt shingles on roofs with a slope up to 4:12 (R905.2.3).
Flashing and Additional Guidelines
- Step flashing for asphalt shingles must be 4 inches high and wide (R905.2.8.3).
- Nails for securing concrete roof tiles need a minimum penetration of 3/4 inch (R905.3.6).
- For cantilevered rafters that are notched, a minimum depth of 3.5 inches must remain (R802.7.1.1).
Wood Shingles and Shakes
- Maximum weather exposure for 16-inch No. 2 wood shingles with a 5:12 pitch is 4 inches (Table R905.7.5(1)).
- Spacing for preservative-treated tapersawn shakes on a roof must be between 3/8 inch and 5/8 inch (R905.8.6).
Valley Flashing and Access
- Sheet metal valley flashing must extend a minimum of 11 inches from the centerline of the valley (R905.8.8).
- Approved hangers are not needed for header to trimmer joist connections if the header joist span is 6 feet or less (R802.9).
- At least 1 inch air space is required between insulation and roof sheathing at eave vents (R806.3).
Miscellaneous
- For attics greater than 30 square feet, no access opening is needed if the attic height is at least 30 inches (R807.1).
- Overflow scuppers for secondary roof drainage must be at least three times the size of the roof drain (R903.4.1).
- A ridge board must be at least 1 inch thick and equal in depth to the rafter cut (R802.3).
- Required total net free ventilating area for a 1,500-square-foot attic, with 75% from upper ventilators, is 10 square feet (R806.2).
- An unvented attic assembly requires minimum 1/4 inch vented air space when using wood shakes (R806.5).
- An ice barrier on asphalt roofs with a 5:12 slope must extend 24 inches inside the exterior wall line (R905.2.7).
- Drip edges must extend 1 inch below roof sheathing at eaves and gables (R905.2.8.5).
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Description
Test your knowledge of the 2015 International Residential Code (IRC) with these flashcards covering Chapters 8 and 9. Explore key definitions and requirements regarding roof drainage, structural supports, and more. Perfect for students or professionals in the construction industry.
