Does a deck on piles cost more than one on footings in Kanata?

Published Ottawa and Ontario builder prices cover new decks at about $25 to $65 per square foot for pressure-treated, $45 to $80 for cedar, $45 to $95 for composite, and $59 to $110 or more for PVC, but those ranges do not break out foundation type separately. We found too few published Ottawa prices to give a standalone figure for helical piles versus concrete footings, so any number a builder quotes you for that difference deserves a line-by-line look rather than a benchmark comparison.

What drives the foundation choice, and its cost, is the soil and the deck itself. A deck that qualifies for the floating-deck exemption under the 2024 Ontario Building Code, meaning it is one storey, not more than 55 square metres, has joists no more than 600 mm above grade, carries no roof, and is either freestanding or where differential movement can be shown not to affect the attached structure, does not need footings dug to frost depth. Once any of those five conditions is not met, the Code's footing-depth rules apply, and the depth must be established on the basis of local experience with frost penetration in that soil.

Soil conditions are lot by lot. Where a builder or engineer finds filled ground, peat, or sensitive clay including Leda clay on a lot, the 2024 Ontario Building Code requires an engineered design under Section 4.2 rather than the standard Part 9 prescriptive rules. Helical piles are a deep-foundation option that falls under that same Section 4.2 design requirement. Whether your lot calls for that is something a builder or geotechnical engineer can tell you after looking at the soil; we found no City of Ottawa map that identifies which lots have sensitive soils.

Before any digging starts, whoever is doing the work, whether a builder or a homeowner, must submit a locate request through Ontario One Call at least five business days before breaking ground. That applies to private property and is required by the Ontario Underground Infrastructure Notification System Act, 2012.

A few things worth confirming with any quote you receive:

• whether the price includes the permit drawings and the City of Ottawa permit fee (calculated at $12.75 per $1,000 of assessed value, minimum $117)
• what foundation type is proposed and why, given your specific lot and deck height
• whether the soil has been assessed or whether that assessment is part of the scope
• what the deck-to-house connection looks like if it is attached, since that must appear on the permit drawings

The City of Ottawa requires three inspections: excavation or foundations before backfill, framing at completion of structural framing and guards, and a final inspection. Book each one 48 hours in advance.

Before you sign a contract for this deck, ask the builder to put in writing who is responsible for applying for the City permit, who books each of the three inspections, and what happens if the foundation design needs to change after the soil is opened up.