What deck joist means
Deck joists are the parallel boards that run between the ledger or beams and carry the deck boards.
Where it matters on a deck job
Joist spacing has to match the decking: many composite boards need closer spacing than wood, and diagonal decking needs closer still. Check the decking maker's span before you lay out joists.
What the model code says
- Joist ends need at least 1 1/2 inches of bearing on wood or metal and 3 inches on concrete or masonry. (IRC 2021, Chapter 5)
Check which code edition your building department enforces for deck joist before you quote.
What it costs
Jobs that involve deck joist are priced in the deck building cost guide: about $11,000 typical, usually $6,650 to $16,500. The guide shows its sources and what moves the price. The deck cost calculator prices a job line by line.
Work it out
- Free calculator: Deck cost calculator
- Cost guide: Deck building cost
- Tools, templates and guides: Free deck resources
Sources: 2021 International Residential Code, Chapter 5, Floors (ICC). Checked October 9, 2026.