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Beam Span Chart Table

The span of a beam is dependent on a few variables: The grade and species of lumber, size of lumber and the load it carries. Fewer posts on upper-level decks are typically more desirable to the occupants and this drives the use of larger framing materials for longer spans. Beam span maximums are based on a maximum anticipated live load as well as other factors. Building codes for residential decks only require 40 psf in some areas, but check your local requirements to make sure you are aware of any additional local guidelines. In addition, many residents prefer the fell of a deck that is designed for higher loads. The longer the joist, the more area of deck the joist supports, and thus the beam supports more area as well.

Dimensional Lumber Deck Beam Span Chart

Note: The span chart below is an example of how spans charts are presented. Because building code and lumber spans are updated from time to time, you should always check to make sure the span chart you are using is up to date. See the applicable code section, or the NDS to confirm the span chart you are using is correct.

Dimensional Lumber Deck Beam Spans Supporting a Single Span of Joists with or without Overhangs:

  Joist Spans
 Species  Size Beam  6'  8'  10'  12'  14'  16'  18'
Southern Pine   2-2x6  6'-8" 5'-8" 5'-1" 4'-7" 4'-3" 4'-0" 3'-9"
 2-2x8  8'-6" 7'-4" 6'-6" 5'-11" 5'-6" 5'-1" 4'-9"
 2-2x10 10'-1" 8'-9" 7'-9" 7'-1" 6'-6" 6'-1" 5'-9"
 2-2x12 11'-11" 10'-4"  9'-2" 8'-4" 7'-9" 7'-3" 6'-9"
 3-2x6  7'-11" 7'-2" 6'-5" 5'-10" 5'-5" 5'-0" 4'-9"
 3-2X8 10'-7" 9'-3" 8'-3" 7'-6" 6'-11" 6'-5" 6'-1"
 3-2X10 12'-9" 11'-0" 9'-9" 8'-9" 8'-3" 7'-8" 7'-3"
 3-2X12  15'-0" 13'-0" 11'-7" 10'-6"  9'-9" 9'-1" 8'-7"

Douglas Fir-Larch,

Hem-Fir,

Spruce-Pine-Fir,

Redwood,

Cedars,

Ponderosa Pine,

Red Pine 

 3X6 OR 2-2X6  5'-2" 4'-5" 3'-11" 3'-7" 3'-3" 2'-10" 2'-6"
 3X8 OR 2-2X8  6'-7" 5'-8" 5'-1" 4'-7" 4'-3" 3'-10" 3'-5"
 3X10 OR 2-2X10  8'-1" 7'-0" 6'-3" 5'-8" 5'-3" 4'-10" 4'-5"
 3X12 OR 2-2X12  9'-5" 8'-2" 7'-3" 6'-7" 6'-1" 5'-8"  5'-4"
 4X6  6'-2" 5'-3" 4'-8" 4-3" 3'-11" 3'-8" 3'-5"
 4X8  8'-2" 7'-0" 6'-3" 5'-8" 5'-3" 4'-11" 4'-7"
 4X10 9'-8"  8'-4" 7'-5" 6'-9" 6'-3" 5'-10"  5'-5"
 4X12  11'-2" 9'-8" 8'-7" 7'-10" 7'-3" 6'-9" 6'-4"
 3-2X6  7'-1" 6'-5" 5'-9" 5'-3" 4'-10" 4'-6" 4'-3"
 3-2X8  9'-5" 8'-3" 7'-4" 6'-8" 6'-2" 5'-9" 5'-5"
 3-2X10  11'-9" 10'-2" 9'-1" 8'-3" 7'-7" 7'-1" 6'-8"
 3-2X12  13'-8" 11'-10" 10'-6" 9'-7" 8'-10" 8'-3" 7'-10"

Assumes 40 psf live load, 10 psf dead load, L/360 simple span beam deflection limit, cantilever length L/180 deflection limit, No. 2 Stress grade, and wet service conditions.