How to Calculate Deck Joist
What is Deck Joist?
Deck Joist Spacing Calculator helps contractors and tradespeople accurately size, spec, and estimate materials and systems.
Formula
Max Span = f(Joist Size, Species, Load) from span table
Step-by-Step Guide
- 1Look up joist span table for species and size, check against deck span
- 2Apply the formula using your project measurements
- 3Add required safety factors or waste allowances per code
Worked Examples
Input
2×8 Doug Fir joists, 40 psf load
Result
Max span at 16 OC = 13 ft-1 inch
Common Mistakes to Avoid
- ✕Not applying code-required safety factors or derating
- ✕Forgetting to account for waste and cut losses in material estimates
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