Deck Foundation Cost Calculator

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Method Comparison

How this estimate works

Footing count is estimated as a grid: posts per beam line = ⌊length ÷ post spacing⌋ + 1, multiplied by the number of beam lines = ⌈depth ÷ joist span⌉ (plus one extra line for a freestanding deck, which needs a beam on both edges). You can override the count. Concrete tube footings: each hole goes to the frost depth plus a 6″ margin; concrete volume = π × (tube radius)² × depth, converted to 30 kg bags (~0.0135 m³ each), plus the tube by the foot, plus a one-time auger + mixer rental if enabled. Deck blocks, DIY screw piles, and pro-installed helical piles are simply the footing count × your editable unit price. Costs are shown ±15%.

What drives the number

Frost depth sets the cost of every hole. Concrete tube footings have to bear below the local frost line, and frost depth varies dramatically across Canada — the same deck can need holes twice as deep in one province as another. Depth drives augering time, tube length, and concrete volume together, which is why this is the first input that matters. A footing that stops short of frost depth will lift and drop with the seasons, taking the deck's geometry and the ledger connection with it.

Footing count comes from spans, not from deck size directly. Wider post spacing needs a bigger beam; a shallower beam needs more posts. The grid above reflects that trade. A freestanding deck needs a beam line on both edges instead of hanging one side off the house, which adds a whole row of footings — one of the real cost differences between attached and freestanding, alongside the ledger work you avoid.

Footing type is a labour-versus-material decision. Concrete tubes are cheapest in material and hardest in labour — augering by hand or with a rented auger, mixing bags, and hoping you don't hit rock. Helical piles installed by a contractor cost several times more per point and take an afternoon, with no spoil, no curing, and no weather dependency. DIY screw piles sit between. On a small deck, tubes usually win; on a large one, or on difficult ground, the pile quote is often closer than expected.

Deck blocks are the cheapest option and the most restricted. They sit on grade rather than below frost, so they move seasonally. That's acceptable for a low, freestanding, ground-level platform in many jurisdictions and unacceptable for anything attached to a house. Check your local rules before choosing them — this is a common source of failed inspections.

Rental costs are lumpy, not proportional. An auger and mixer are a fixed day rate whether you dig six holes or sixteen, so the per-footing cost falls sharply on bigger decks. On a very small deck, mixing by hand and skipping the rental may genuinely be cheaper.

What this estimate does not include

• Everything above the footings — posts, beams, joists, decking, railings, stairs. Price those with the Deck Cost Calculator.
• Post bases and structural hardware connecting posts to footings, which code generally requires and which stop posts from sitting in standing water.
• Rock, roots, and buried surprises. An auger stopped by a boulder a metre down turns a routine hole into an afternoon. Multiple obstructions can force the whole layout to move.
• Utility locates. Free in most of Canada, mandatory before digging, and skipping them risks striking gas, hydro, or telecom. Call before you auger — no exceptions.
• Labour, if you're not doing it yourself.
• Permit and inspection. Many municipalities inspect footings before concrete goes in, which means scheduling around their availability rather than yours.
• Spoil disposal — a surprising volume of soil comes out of a dozen deep holes, and it has to go somewhere.
• Cold-weather work. Concrete placed near freezing needs protection, and frozen ground is a different digging job entirely.

For why frost depth governs all of this and what happens when it's ignored, see Deck Foundations & Frost.