How much does it cost to add a legal secondary suite to my Ottawa home?

A legal secondary suite can house a family member or provide rental income, but the standards that make a suite legal add cost compared with a basic renovation. The total depends mostly on whether you convert existing space, such as a basement, or build a new addition for the suite.

As broad perspective, a legal secondary suite can range from roughly $80,000 to $180,000 depending on the starting point, size and finishes. Treat that as perspective, not a quote.

Basement conversion. This usually involves a separate entrance, fire separation between the units, bedroom windows that meet egress rules, a full kitchen and bathroom, heating and ventilation for the suite, and electrical work. If the basement is too low for the ceiling heights the Building Code requires, underpinning to lower the floor adds a large cost. Your designer will confirm the height requirements for each room.

New addition as a suite. Building the suite as an addition means a new foundation, with footings at least 1.2 m deep on clay or poorly defined soils and not shallower than the depth of frost penetration, plus everything a self-contained home needs.

Fire separation. For new construction, the Code calls for a 45-minute fire separation, or 15.9 mm (5/8 in) Type X gypsum on both sides of separating walls and on the underside of the floor-ceiling framing. For a unit created inside an existing house, Part 11 compliance alternatives can allow a 15-minute separation with interconnected smoke alarms. Your designer confirms the exact assembly.

Permits. The City always requires a building permit for a secondary unit, and the drawings must show the fire-separation walls and floor-ceiling construction. The 2026 fee for alterations and additions is $12.75 per $1,000 of construction value (minimum $117). Electrical work needs an ESA notification, and gas work is done by a TSSA-certified gas technician.

Other costs to check. Ask the City whether any development charges or other fees apply to a new unit on your property, and ask MPAC or your accountant how the suite might affect your property assessment and taxes. If you plan to rent, an accountant can help you think through rental income and taxes.

Tax credit. If the suite is for a senior or an adult eligible for the disability tax credit to live with a qualifying relative, the federal Multigenerational Home Renovation Tax Credit covers up to $50,000 of qualifying expenses at 14.5 per cent (a maximum of $7,250). The unit needs its own private entrance, kitchen, bathroom and sleeping area.

To compare itemized quotes, browse renovation and addition contractors who have built secondary suites in the Ottawa Construction Network directory at justynrookcontracting.com.

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Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:

• 613Bins
• RenoMotion Inc.
• JMY Renovations
• Joe Imerti Contracting
• M.O.T. CONSTRUCTION INC.