Attic Access

Attic Access Requirements

1. Provide an access opening to every attic with at least () 30 square feet of attic area and a vertical height of at least () 30 inches at some point in the 30 square feet. Measure the vertical height from the top of the ceiling joists (or truss bottom chord) to the bottom of the rafters (or truss top chord). Read the full Topic

Attic Ventilation

Attic Ventilation Requirements

1. Provide ventilation to attic spaces, unless you design and build the attic as an unventilated, conditioned attic assembly. Provide ventilation when ceilings are applied directly to roof rafters, such as cathedral and vaulted ceilings, and in attics over unconditioned spaces, such as garage attics. Provide ventilation to each individual attic and ceiling space, unless there is eff ective means for air to move between spaces. The building official may waive att ic ventilation requirements. Read the full Topic

Ceiling Joist and and Rafter Framing Details

Ridge, Valley, and Hip Rafter Framing

1. Install at least () a 1 inch (nominal thickness) ridge board at roof ridges. Install a ridge board that is at least () as deep as the (plumb) cut end of the rafter. Install rafters directly across from each other at the ridge board. You may omit the ridge board if you secure the rafters to each other with a gusset plate. Read the full Topic

Ceiling Joist and Rafter Boring and Notching

 Ceiling Joist and Rafter Notching

1. Notch structural dimension lumber ceiling joists, rafters, blocking, and beams not deeper than () one-sixth of the actual depth of the member. Notch the member not longer than () one-third of the actual depth of the member. Do not place any notches in the middle one-third of the member. Example: notch a 2×8 ceiling joist not more than () 1 ¼ inches deep and not more than () 2 ½ inches long.

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Ceiling Joist and Rafter Openings

Joist and Rafter Openings Description

Common reasons for openings in ceiling joists and rafters include openings for attic access (scuttleholes and pull-down stairs), openings for whole house fans and skylights, and framing for dormers or similar structures. The header joists distribute the load of the tail joists to the trimmer joists. Read the full Topic

Ceiling Joist and Rafter Spans

An attic with limited storage is designed with an additional 10 pounds per square foot live load compared to an attic without storage. Verify the storage capacity of truss-built attics with the truss engineer before using the attic for storage.

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When Gutters are Required

1. Provide gutters or other means to control roof runoff in areas with expansive or collapsible soil. Discharge the gutter water at least () 5 feet away from the foundation or into an approved drainage system. Read the full Topic

Mineral-Surfaced Roll Roof Covering Material

Mineral-Surfaced Roll Roof Covering Description

Mineral-surfaced roll roofi ng material usually comes in 36 inch wide rolls. It is usually a lower quality and less expensive roof covering material compared to other roof covering materials. It is commonly used on temporary buildings, accessory buildings, low slope porch roofs, and in other applications where long life is not critical. Roof slopes are shown as x/y where x is the number of vertical units rise and y is the number of horizontal units run. A 4/12 roof has 4 vertical units rise for every 12 horizontal units run.

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Roof Uplift Resistance

1. Attach trusses and rafters to the supporting walls using either 3-16d box nails (3½ in. x 0.135 in.) or 3-10d common nails (3” x 0.148 in.). Toe nail the trusses and rafters to the top plate placing two nails on one side and one nail on the other. This applies when: (a) roof uplift force is not more than () 200 pounds and the trusses and rafters are spaced not more than () 24 inches on center; Read the full Topic

Wood Truss and Installation and Bracing

Truss Design and Bracing Written Specifications Requirements

1. Use a qualified engineer to design all wood trusses such as roof and floor trusses. The engineer or truss manufacturer should provide written truss design and installation specifications and deliver them to the job site with the trusses. These specifications should include engineering information, such as chord live and dead loads, and assembly information, such as the size, species, and grade of each truss member, and installation instructions, such as where each truss should be located on the structure and how the trusses should be permanently braced. Read the full Topic