Does my septic system affect where an Ottawa deck can go?

Yes, your septic system affects both where a deck can go and what the permit drawings must show. The City of Ottawa's permit requirements ask for a site plan that dimensions the deck relative to "any septic system" on the property, so the septic system has to appear on those drawings.

Beyond the drawing requirement, there are two practical concerns that shape placement. First, zoning setbacks under both Zoning By-law 2008-250 and Zoning By-law 2026-50 apply to a deck as a structure, and the most restrictive provisions of both by-laws govern any application deemed complete on or after March 11, 2026. Those setbacks are measured from lot lines, so the septic system and the setbacks are two separate checks. You should confirm the current rules for your specific lot with the City.

Second, footings. The 2024 Ontario Building Code sets footing depth requirements based on soil type, and where a foundation is on filled ground, peat or sensitive clay, an engineered design is required under Ontario sections 9.15.1.1(3) and (4) and 9.4.4.1(3). A designer or engineer reviewing your lot can tell you whether that applies.

A few things to sort out before the drawings are finalised:

• the septic system shown on the site plan, dimensioned to the deck
• where each footing sits relative to it
• whether the deck height triggers the permit requirement: attached to the house with a walking surface more than 600 mm (24 in.) above grade requires a permit, as does an elevated deck providing principal access to the building
• whether the deck is freestanding and over 10 square metres (approximately 108 square feet) with a walking surface more than 600 mm above grade, which also requires a permit

If any footing needs to be dug, the Ontario Underground Infrastructure Notification System Act, 2012 requires that a locate request be submitted through Ontario One Call and that each affected member respond before any digging starts. That applies whether a contractor digs or you do it yourself, and private lines such as a septic system's own piping are yours to have marked separately.

The next step is to request a locate through Ontario One Call before any test holes or footing excavation, and then make sure the site plan shows the septic system with the required dimensions.