Deck Joist Length Guidelines

1. Footings must bear on solid ground below the frost line to prevent frost heave. Depth of frost line varies by geography
2. The bearing capacity of the soil is presumed to be at least 2000 pounds per square foot (psf)
3. Load per square foot is presumed to be 50 pounds per square foot (40 psf live load / snow load + 10 psf dead load)
4. For decks with an overhang, double the length of the overhang and add to joist length. For example, if 10 foot joist is used with a 2 foot overhang, double the overhang (4) and add to existing joist length (4 + 10 = 14) You will then use 14 feet as your joist length in the above chart.

Example: If your joist length is 15 feet, and posts are spaced 5 feet apart, you would use a 16″ diameter footing UNLESS the footing is at an outside corner
Note: The FootingPad Size Chart is calculated from test data as certified in ESR-2147 on 2000 psf soil / 50# psf load.