Deck framing & structure

How this pillar fits together

A deck frame is a load path. The decking sits on joists, the joists sit on a beam or hang off a ledger, the beam sits on posts, and the posts stand on footings in undisturbed soil below the frost line. Every page in this pillar sizes one link of that chain, and each one hands its answer to the next.

Work it top down. The decking you choose sets the joist spacing. The joist species, size and spacing set how far a joist may span, read from the code's joist table. That span sets how much deck leans on the beam, which with the beam's size and ply count sets how far apart the posts can stand. Post spacing and joist span together give each footing its share of the deck, and the soil under it decides how big that footing has to be.

The numbers come from the model code's deck section, which most US jurisdictions adopt with local amendments: joist spans, beam spans, post heights, footing sizes, the ledger connection, guards and stairs. Where a page quotes a table it says which one and when it was read. None of it replaces your building department's adopted edition, and point loads such as a hot tub sit outside every prescriptive table.

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