Lumber Spans
12-24" spacing -- 16" is typicalMaximum canilever: 24"Maximum beam overhang: 12"Maximum beam overhang: 12"I always make a notch for the beam to sit on.Why depend on anchor bolts when you can use the whole post?Go to beam size and span data?I always use 6x6 posts, anchored with metalI always use 6x6 posts, anchored with metal.Never more than 11 ft -- optimize use to save cost and yardspace.Go to lumber span data?Always a 2 x 10 ledger, flashed, bolted and caulked.See Table BelowSee Table Below

The lengths shown indicate just how far the lumber can span before you need to add more support. How is this information useful in planning? For example, you can see that by using 2x10 joists and spacing them 16 inches apart--the most common application--you can run your deck out 13'3" from the house and support it with posts there.

But suppose you have a concrete patio right in that spot: Two solutions illustrated here are 1) move the joists closer together, or 2) use 2x12 joists instead.

JOIST
SPACING
& SIZE
12" o.c.
16" o.c.
24" o.c.
2x6 9'2" 8'4" 7'0"
2x8 12'1" 10'10" 8'10"
2x10 15'4" 13'3" 10'10"
2x12 17'9" 15'5" 12'7"

 

  • All framing is figured with Ponderosa Pine to a rating of 40#/sq.ft. (although the actual wood species includes Spruce, Pine and Fir, SPF)  live load. Southern Pine has longer span potential, and is available for special circumstances.

  • Joist length is total length of joist, including any cantilevers.

  • W    hen joist extends (cantilevers) beyond support beam by 18" or more, add 1" to footing dimensions shown below.

Beam Sizes:

Use the beam size indicated by the spacing of your planned posts and the span of the joists.

 

Based on No.2 or better Ponderosa Pine, treated for weather and/or ground exposure