Then you better know how to compute the spans for it to be structurally sound.
These tips and this information will help.
Before building a deck, take the time to look up your local codes.
Credit: Keller and Keller
The following guide will walk you throughbasic deck requirementsand best practices for calculating deck joist and beam spans.
Hem-fir is a designation that includes hemlock, fir, and other species that grow in the same stands.
Some hem-fir is solid and stable, while some is weak and likely to warp and crack.
Consult with a lumber dealer and your local building department before using hem-fir.
Lumber quality also has a bearing on a board’s strength.
2 and better are the best choices for deck building.
Construction grade, common, and No.
3 stock have defects that make them unsuitable for a deck.
“Select grade” or No.
1 boards are top-quality but are usually not worth the extra cost for use in deck building.
If a site has marshy or sandy soil, massive footings may be required.
4x4 lumber is strong enough for structural posts with a 2x6 span for most projects.
The calculations below list approximate recommended deck beam spans.
For instance, a beam made of two 2x8s is probably stronger than a solid piece of 4x8.
They are also less likely to crack.
Deck Beam SpansDistance between ports, using No.
2 and better Southern pine or Douglas fir.
It also depends on the joist spacing.
For instance, deck joist spacing 24 inches apart requires wider joists than deck joists placed 16 inches apart.
See the deck joist calculations below and study your local code.
Deck Beam SpansDistance a joist spans between a beam and a ledger or between beams, using No.
If you use 5/4 decking, joists must be no farther apart than 16 inches.
Decking with boards with a 2x4 or 2x6 span can be 24 inches.
If you run decking at an angle, you might need to put the joists closer together.
Again, it’s essential to know your local codes.
While a few requirements might seem dated or unusual, most are based on the following common concerns:
