Deck Joist Span Calculator

AnvilField

About this app

Type in your deck once and export a cited PDF planning set with a framing plan, member schedule, footing schedule, and IRC R507 basis notes.

How far can a 2x8 deck joist span? For Southern Pine No.2 at 16" o.c., DeckFrame allows 10'-11" at its 40 psf live basis — computed from NDS design values, shown right next to your actual span, and everything downstream (beam, footings, ledger) sizes from the same answer.

SIZE IT
Set the deck's length, projection, height, species, and load basis (40 psf live, ground snow bands to 50, 60, and 70 psf). Joists by size and spacing (12/16/24" o.c.), cantilevers keyed to the back span and capped at span/4, 2- and 3-ply drop beams with max post spacing, footing diameters from tributary load and the soil bearing YOU enter (with frost depth), and the 1/2" lag ledger fastener schedule all solve from one model. Move one number and the whole deck re-solves — stretch the joist span and the beam, footings, and ledger schedule update with it.

CHECK IT
Every member shows its allowable span beside your actual span with the table it came from. The guard post connection gets the 200 lb load-path check. And DeckFrame refuses to extrapolate: ground snow over 70 psf, engineered lumber, multi-level framing, hot-tub loads, or spans past the table limits come back "engineer required," so unsupported inputs are clearly identified instead of given a guessed number.

PRINT IT
Export the PDF planning set: framing plan and elevation with member callouts, member schedule, footing schedule, ledger detail, section citations, and a lumber bill of materials. It is formatted for review with your qualified professional and AHJ; acceptance depends on locally adopted code, amendments, and project requirements. No subscription, no watermark on the export, no paywall between you and the beam size.

Decks save on the phone and reopen right where you left off, layout day to final — duplicate one for the next job. A legacy DCA6-2015 mode covers jurisdictions still on older code (40 psf live only; the app flags decks outside that basis).

SOURCES AND DISCLAIMER
Span results are computed from published NDS reference design values following the 2021 IRC R507 method; the Reference tab lists every constant and where it came from. DeckFrame is a planning aid, not a substitute for a qualified professional, your locally adopted code and amendments, or AHJ review. IRC is a trademark of the International Code Council. NDS and DCA6 are publications of the American Wood Council. Not affiliated with or endorsed by ICC or AWC.

No account, no ads, and no network permission — everything runs offline and free, and your decks never leave the phone.

SUPPORT
See a span that looks wrong? Email [e-mail] — span reports get first priority.

What’s new

Updated deck joist span calculator identity, framing inputs, cited planning output, and PDF preview.