Two quotes use different foundations for my Barrhaven deck; which to trust?

Neither foundation type is automatically more trustworthy than the other. What matters is whether the foundation shown on the permit drawings is sized and specified for your deck's height, load, soil conditions and attachment to the house, and whether the builder can explain why they chose it.

The 2024 Ontario Building Code sets the starting point. For a deck attached to the house with a walking surface more than 600 mm (24 in.) above grade, the City of Ottawa requires a building permit, and the permit drawings must show the footing or foundation type, size and location, or a helical pile layout and specifications. The City lists three required inspections: Excavation/Foundations before backfill, Framing at completion of structural framing and guards, and a Final inspection. That means the foundation choice goes on paper and gets inspected, so it cannot simply be left to the builder's preference on the day.

Under the Code's Table 9.12.2.2, footings in clay or soils not clearly defined must reach at least 1.2 m below grade, but not less than the local frost penetration depth, which Ontario says is established on the basis of local experience. If the soil on your lot is sensitive clay, including Leda clay, the Code at sections 9.15.1.1(3) and (4) and 9.4.4.1(3) requires an engineered design rather than the standard prescriptive footing tables. A builder or an engineer can tell you whether that applies to your lot. The City's permit list also asks for helical pile layout and specifications where piles are used, because piles are deep foundations and fall under Section 4.2 engineered design. Neither foundation type is simpler or more straightforward in every situation: the right choice depends on your soil, the deck's size and height, and whether it is attached to the house.

A few things worth checking on each quote:

• Does the quote reference permit drawings, and do those drawings show the foundation type, size and depth?
• Who is taking design responsibility on Schedule 1: a BCIN designer, an engineer, or the homeowner exemption?
• If the soil turns out to need engineered design, is that included or priced separately?
• Who applies for the permit and books the three City inspections?
• Before anyone digs, has a locate been requested through Ontario One Call? Under the Ontario Underground Infrastructure Notification System Act, 2012, no excavation can start until each affected utility member has responded, which takes up to five business days. This applies to both foundation types.

The permit fee from the City is $12.75 per $1,000 of assessed valuation (materials, labour, overhead and professional fees combined), with a minimum of $117. As an illustration: a $15,000 deck works out to $191.25. Published Ottawa and Ontario builder prices for a new installed deck run roughly $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, though the spread is wide and some published packages exclude railings and steps.

You can request quotes from local deck builders listed in the Ottawa Construction Network directory through the form on this page.

Before work starts, make sure you have the signed permit drawings, the issued building permit and a written contract that sets out the full scope, the foundation specification and the total price.