Do supporting beams need Type X in an Ottawa house with a suite?

Ontario's Building Code requires that light-frame walls, columns, arches and beams that support floors between dwelling units in a house with a secondary suite be protected by not less than 5/8-inch (15.9 mm) Type X drywall (clause 9.10.8.3.(2)).

These are minimums for new work, and the City decides through the permit how they apply to your renovation, so confirm the scope with the City's Building Code Services before any board goes up.

What this means for the beams in your house

The 5/8-inch Type X rule for structural members sits alongside the broader separation between the two units. For new work, Ontario's Building Code gives two routes for that separation: a fire separation rated at 45 minutes (clause 9.10.9.16.(1)), or a continuous smoke-tight barrier of 5/8-inch Type X on both sides of walls and on the underside of floor-ceiling framing (clause 9.10.9.16.(4)). The Code also waives the Type X barrier route where the house is sprinklered throughout (clause 9.10.9.16.(5)); ask the City how that applies. The beam rule in 9.10.8.3.(2) is a separate sentence of the Code, so ask the City how the two fit together on your drawings.

For an existing house being converted, Part 11 of the Code includes a compliance alternative (C156) that accepts a 15-minute horizontal fire separation where smoke alarms are installed in every dwelling unit and common area and are interconnected. The Code text we have does not specify which assembly achieves 15 minutes, and the City decides which route applies through the permit.

A few things worth asking the contractor and the City before work starts:

• Which separation route the permit drawings will show, because that affects what board goes where throughout the floor-ceiling assembly, not just on the beams.
• Whether any openings in that assembly, such as pot lights or duct penetrations, need to be addressed to keep the barrier continuous (clause 9.10.9.2 requires continuity).
• What the permit drawings show for the wall and floor-ceiling construction between the new unit and the main dwelling: the City's adding-an-apartment page says the drawings must show it.

Before any 5/8-inch Type X is ordered, ask the City's Building Code Services which separation route your permit drawings should show for your house.