Several Factors Determine The Deck Joist Span For Your Deck

The proper deck joist span (distance between supporting beams below the joists) for your deck should be known before you start building and is needed to draft your deck plan.

The spans of joists varies based upon several factors: joist size, spacing between joists, decking material and wood species.

First Step: Select a Wood Species

Select your decking material.

Refer to the Decking Span Table to determine what is the maximum distance that your chosen decking can span between joists.

For example 2x6 materials can usually span 24” without any noticeable deflection and still support a significant load. However, lumber prices are rising and therefore it is more common to see 5/4”x6 deck boards that should not span more that 16” and usually 12”.

Once you know your decking material and its maximum recommended span you can then refer to the deck Joist Span Table below.

Second Step:

The Joist Span Table below will assist in determining the maximum length your joists should span between supporting beams, bearing in mind that these distances reflect the strength capacity of the joists only.

Also, remember this simple concept to assist you.

The closer you space joists together, the greater length you can span joists – up to a point. The numbers in this chart indicate the maximum span you can use based on the type of wood and the spacing you have chosen. You are now “good to go”!

Deck Joist Span Table

**Table does not account for overhangs.

Species Maximum Distance Between Posts or Supports
Joist Size 12" o.c. 16" o.c. 24" o.c.
Southern Pine 2x8 13'-8" 12'-5" 10'-2"
2x10 17'-5" 15'-10" 13'-1"
2x12 18'-0" 18'-0" 15'-5"
Douglas Fir-Larch,
Hemlock-Fir,
SPF
2x8 12'-6" 11'-1" 9'-1"
2x10 15'-8" 13'-7" 11'-1"
2x12 18'-0" 15'-9" 12'-10"
Redwood,
Western Cedars,
Ponderosa Pine,
Red Pine
2x8 11'-8" 10'-7" 8'-8"
2x10 14'-11" 13'-0" 10'-7"
2x12 17'-5" 15'-1" 12'-4"

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