Calculate the number of footings, sonotube size, depth below frost line, concrete needed, and post size for your deck. Includes frost line data for every US state and Canadian province.
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Deck footings must extend below the frost line for your region. In Ontario, footings should be at least 48 inches deep. In Texas, 12 inches may suffice. Always check your local building code for the exact requirement.
Most residential decks need footings spaced 6-8 feet apart in both directions. A typical 12x16 deck requires 6-9 footings depending on the load and whether it's attached to the house or freestanding.
For most residential decks, 10-inch sonotubes are standard. Use 8-inch for lightweight, low decks and 12-inch for heavy loads like hot tubs, multi-story decks, or poor soil conditions like clay or sand.
Each footing requires a volume of concrete based on the tube diameter and depth. A 10-inch sonotube at 48 inches deep needs about 0.018 cubic yards of concrete, or roughly 2 bags of 30kg premix per footing.
In most municipalities, any deck that requires footings also requires a building permit. Permits ensure footings meet frost depth requirements, load capacity, and setback rules. Always check with your local building department before digging.
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