calcs.homes
calcs.homes
Enter your deck's size to find the total design load it needs to support under standard residential code values.
Estimate only — actual framing capacity depends on joist size, spacing, and span. Have a professional verify.
Total design load is deck area multiplied by live load (people, furniture, movable weight) plus dead load (the deck's own structural weight) per square foot. US residential code typically requires at least 40 psf live load and accounts for about 10 psf dead load — 50 psf total. Estimated occupancy assumes about 200 lb per person, a conservative planning figure, not a hard code limit.
40 psf (pounds per square foot) is the standard US residential code minimum for typical decks — hot tubs and other concentrated loads usually need engineered framing beyond this baseline.
This calculator gives a rough capacity based on code live load and an average 200 lb per person — but actual safe occupancy also depends on how the load is distributed and whether the deck was built to code. A structural inspection is the only way to know for certain, especially on an older deck.