How much does it cost to add fire separation between an in-law suite and main house in Ottawa?

Fire separation between an in-law suite and the main house isn't optional. When you create a self-contained secondary unit, the City always requires a building permit, and the drawings must show the fire-separation wall and floor-ceiling construction. The cost depends on whether the separation is designed into new construction or retrofitted into an existing house.

What the Code asks for. For new construction, the Ontario Building Code calls for a 45-minute fire separation between the units, or 15.9 mm (5/8 in) Type X gypsum board on both sides of the 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 when interconnected smoke alarms are provided. Your designer confirms the exact assembly for your house, and the inspector checks it before it is covered.

New addition built as a suite. When the suite is a new addition, the separation is drawn into the plans from the start. The extra cost is mostly the Type X gypsum on the separating wall and ceiling, sealing at penetrations, and the doors between the units. It is usually a modest share of the addition's budget.

Retrofit in an existing house. Retrofitting usually costs more, because finished walls and ceilings often have to be opened to check the framing, add blocking and seal every hole. Electrical boxes, pipes, ducts and anything else that passes through the separation must be sealed with fire-stopping products that suit the assembly. The amount of demolition and refinishing is what drives the price, so ask contractors to quote after seeing the space.

Doors. The doors between the suite and the main house are part of the separation. Ask your designer what door and closer the drawings require, and don't substitute an ordinary interior door without checking.

Smoke alarms. Smoke alarms in both units, and interconnection between them, are part of the plan, especially where the Part 11 alternative is used. Hardwiring them is electrical work that needs an ESA notification.

The permit and drawings. Because the separation details must be on the drawings, it is worth having a designer who has done secondary units before. If the suite is for a senior or an adult eligible for the disability tax credit, the federal Multigenerational Home Renovation Tax Credit may help with qualifying costs, up to $50,000 of expenses at 14.5 per cent, for a self-contained unit with its own entrance, kitchen, bathroom and sleeping area.

Ask for the fire separation as a separate line on each quote so you can compare. You can browse contractors with in-law suite experience 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:

• Justyn Rook Contracting
• RenoMotion Inc.
• Prism Services
• Renovo Construction
• Demontigny Carpentry