Deck Footings Calculator
Calculate the number of footings, concrete, sono tubes, and post anchors needed for your deck. Includes frost depth and soil considerations.
How to Use This Calculator
Proper footings are the foundation of a safe, long-lasting deck. This calculator helps you determine the number of footings needed and the concrete required for your project.
- Enter your deck dimensions in feet (length from house, width parallel to house).
- Specify beam spacing - typically 6-8 feet depending on joist size and span tables.
- Enter footing diameter (12 inch is standard residential, larger for heavy loads).
- Enter footing depth - must be below your local frost line.
- Indicate if the deck attaches to the house (ledger mounted) or is freestanding.
Why This Matters
Deck footings transfer the entire weight of your deck - including furniture, people, and snow loads - to the ground. Undersized or improperly placed footings can lead to deck settling, structural failure, or frost heave damage. Most building codes have specific requirements for footing size, depth, and spacing.
- Calculate the correct number of footings for your deck size
- Determine concrete quantities for budgeting
- Check if footing size is adequate for soil conditions
- Plan sono tube and anchor hardware needs
- Estimate complete footing material costs
Worked Examples
Standard 12x16 Deck
A 12' x 16' deck attached to house with 8-foot beam spacing.
Large Freestanding Deck
A 16' x 20' freestanding deck with 6-foot beam spacing.
Deck with Hot Tub
A 14' x 18' deck with hot tub area requiring larger footings.
Common Mistakes to Avoid
- Not digging below the frost line - causes heaving and structural damage.
- Footings too small for the load - leads to settling and structural problems.
- Incorrect spacing - too few footings overloads each one, too many wastes money.
- Not using sono tubes - makes it hard to get consistent diameter and clean edges.
- Forgetting post anchors - posts must be mechanically connected to concrete.