FLOOR CONSTRUCTION

Concrete Slab-On-Grade Floors

Concrete Thickness and Strength

1. Make concrete slab-on-grade floors at least () 3 ½ inches thick. This does not include extra thickness for footings and interior bearing walls. Read the full Topic

Decks

Deck Attachment to the Building General Requirements

1. Design decks to resist both vertical and horizontal (lateral) loads where the deck is attached to the building. Read the full Topic

Floor Joist Openings

Floor Joist Openings Description

Framed openings in floor joists are mostly used for stairways between floors and for chimneys. The header joists distribute the load of the tail joists to the trimmer joists.

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Floor System Fire Protection

Fire Protection of Floor Framing

1. Install at least () ½ in. thick gypsum drywall, thick wood structural panel, or equivalent material on the under side of I-joist type floor joists, metal plate connected floor trusses, and dimension lumber joists smaller than (<) 2X10 unless an exception applies. This provision does not apply if the floor system is required to be fi re-resistant by another code provision.  Read the full Topic

Manufactured Wood Floor Trusses and Joists

Wood I-Beam Floor Joists Notching and Boring

1. Notch, bore, splice or alter wood I-Beam (TJI-type) floor joists only as specified by the manufacturer’s instructions. Altering the top and bottom flange is usually not allowed. Hole boring is usually allowed in the middle third of the span and is restricted near the joist ends.

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Wood Floor Framing

Cantilever Definitions

Backspan: Backspan is the part of a cantilevered joist within the supporting wall.

Cantilever: A cantilever is an extension of a floor joist beyond a supporting wall or beam. The distance that one may cantilever a floor joist depends on the width of the

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Wood Floor Joist Boring and Notching

Boring and Notching Definitions

Bore: A bore is a hole drilled in a stud or joist. Use the actual dimensions to determine the depth of framing lumber and when calculating the maximum hole diameter.

Notch: A notch is a piece cut from the smaller dimension of framing lumber such as a stud or joist. Use the actual dimensions to determine the depth of framing lumber and when calculating the maximum notch depth. Actual dimensions are the dimensions of framing lumber after finishing at the mill. Example: the nominal dimensions of a 2×6 are 2 inches by 6 inches and the actual dimensions, after finishing, are about 1 ½ inches by 5 ½ inches.

Example: the actual depths of a 2×8 and a 2×10 are about 7 ¼ and 9 ¼ inches.

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Wood Floor Joist Spans

Floor Joist Span Tables

1. Use 30 psf live load and 10 psf dead load for most joists under bedrooms and in attics with access by permanent stairs, in most cases. Permanent stairs do not include pull-down folding attic ladders. Read the full Topic

Wood Structural Panel Sheating

Limitations of the Material in this Section

The IRC presents many combinations of materials and installation techniques for installing wood structural panels as sheathing on roofs and as subflooring and underlayment. This section includes common materials and installation techniques used in modern residential construction. Refer to the IRC for information about less common materials and installation techniques.  Read the full Topic