Floor Joists Span Chart for 2012 IRC

The floor Joist span chart and building code requirements are based on data from the 2012 International Residential Code using number 2 lumber.

Types of Floor Joists

Joists for use in residential framing applications fall into two different categories; tree sawed and engineered. This page focuses on the tree sawed variety. Kiln dried number 2 Pine is the most widely used material. It is relatively inexpensive and is widely available. It is available in sizes that will work for joists from 2 x 8 x 8′ to 2 x 12 x 24′. There are limits on how far these boards can span. 

Floor Joist Span Chart for 40 lb Live Load

O.C. Type of Wood 2×8 2×10 2×12
12″ Southern Pine 14’2″ 18′ 21’9″
  Hem-Fir 13’2″ 16’10” 20’4″
  Douglas Fir 14’2″ 17’9″ 20’7″
  Spruce-Pine-Fir 13’6″ 17’3″ 20’7″
16″ Southern Pine 12’10” 16’1″ 18’10”
  Hem-Fir 12′ 15’2″ 17’7″
  Douglas Fir 12’7″ 15’5″ 17’10”
  Spruce-Pine-Fir 12’3″ 15’5″ 17’10”
19.2″ Southern Pine 12’1″ 14’8″ 17’2″
  Hem-Fir 11’3″ 13’10” 16’10”
  Douglas Fir 11’6″ 14’1″ 16’3″
  Spruce-Pine-Fir 11’6″ 14’1″ 16’3″
24″ Southern Pine 11′ 13’1″ 15’5″
  Hem-Fir 10’2″ 12’5″ 14’4″
  Douglas Fir 10’3″ 12’7″ 14’7″
  Spruce-Pine-Fir 10’3″ 12’7″ 14’7″

Floor Joist Span Chart for 30 lb Live Load 

O.C. Type of Wood 2×8 2×10 2×12
12″ Southern Pine 15’7″ 19’10” 24’2″
  Hem-Fir 14’6″ 18’6″ 22’6″
  Douglas Fir 15’7″ 19’10” 23′
  Spruce-Pine-Fir 14’11” 19′ 23′
16″ Southern Pine 14’2″ 18′ 21’1″
  Hem-Fir 13’2″ 16’10” 19’8″
  Douglas Fir 14’1″ 17’11” 19’11”
  Spruce-Pine-Fir 13’6″ 17’2″ 19’11”
19.2″ Southern Pine 13’4″ 16’5″ 19’3″
  Hem-Fir 12’5″ 15’6″ 17’1″
  Douglas Fir 12’10” 15’8″ 18’3″
  Spruce-Pine-Fir 12’9″ 15’8″ 18’3″
24″ Southern Pine 12’4″ 14’8″ 17’2″
  Hem-Fir 11’4″ 13’10” 16’1″
  Douglas Fir 11’6″ 14’1″ 16’3″
  Spruce-Pine-Fir 11’6″ 14’1″ 16’3″

Floor Joist Building Code Requirements

The best way for a joist to transfer its load is for it to stack. This simply means for it to rest directly on top of another framing member like a drop girder, a wall, or a pressure treated mud sill. There is some criteria the joists must meet according o the 2012 International Residential Building Codes.

  • The joist must have a minimum of 1 1/2″ riding on the wall or beam.
  • If the joists are lapped, then they must be lapped at least 3″.
  • Maximum end notches for 2 x 8, 2 x 10, and 2 x 12 respectively are 1 13/16″, 2 5/16″, and 2 13/16″.
  • Use an approved hanger or a 2 x 2 ledger strip on flush beams for spans greater than 12′.
  • When framing openings, use header and trimmer joists. Double any header over 4′ and any trimmer joists with a header attached within 3′ of its bearing.
  • Use a minimum of 3 8d nails for toe nailing to girder or sill.
  • Use a minimum of 3 10d nails for face nailing and lap joints.

Be aware that these spans and code requirements are taking things to the absolute limit. In a practical application it is a good rule of thumb to not use 2 x 8’s at all, never span a 2 x 10 over 14′, never span a 2  x 12  over 20′, and use as many nails as possible without damaging the wood.

Floor Joist Installation