Deck Footings and Framing
The part you don’t see — footings, posts, beams and joists — is most of a deck’s labor and the part codes care about most.
Footings and posts
Footings must go below the local frost line and be sized for the load; posts carry the beams to those footings. Spacing and size come from span tables and code — under-size them and the deck fails inspection or worse.
Beams and joists
Joists at 12–16 inches on center span between beams; beam size depends on the joist span. Composite and diagonal decking usually need tighter joist spacing. Count joists, beams and hardware in the deck calculator, not just the surface boards.
FAQ
How deep should deck footings be?
Below the local frost line and sized for the load — depth varies by region, so check local code before pricing.
How far apart are deck joists?
Usually 16 inches on center for wood, and 12 inches for composite or diagonal decking to prevent sag.