How do City of Toronto inspectors verify that the correct type of fire-rated drywall was installed?

Toronto building inspectors verify fire-rated drywall primarily through visual inspection of the board markings, assembly configuration, and documentation — but the window to verify is narrow, which is why calling for inspection before boarding is closed is critical.

What Inspectors Actually Look For

Every sheet of fire-rated drywall manufactured to ULC (Underwriters Laboratories of Canada) standards is required to carry printed markings on the back face of the board. These markings identify the board type (Type X or Type C), the thickness, the fire-resistance rating, and the manufacturer. An inspector can read these markings directly off exposed board edges, at cut-outs around electrical boxes, or at any point where the board face is visible. On a properly installed garage fire separation, for example, the inspector will look at the board edges visible at the door frame rough opening to confirm 5/8-inch Type X is in place.

Inspectors also verify the assembly configuration, not just the board type. A single layer of 5/8-inch Type X on the garage side of a garage-to-house separation achieves the required 45-minute fire resistance under Ontario Building Code — but only when the joints are taped and finished, all penetrations (electrical boxes, pipes) are properly fire-stopped, and the door opening contains a solid-core or fire-rated door with a self-closing device. Installing the right board but leaving gaps, untaped joints, or an unsealed penetration voids the fire rating of the entire assembly. Inspectors check all of these elements together.

For assemblies requiring a full 1-hour or 2-hour fire resistance rating — condo party walls, furnace room enclosures, or stairwell separations — inspectors will verify the complete ULC-listed assembly, which specifies the exact board type, number of layers, fastener schedule, stud spacing, and any required resilient channel or acoustic treatment. These assemblies are tested as a system, and substituting components (using Type X where Type C is specified, or reducing from two layers to one) fails the assembly even if the individual boards are fire-rated.

The Timing Problem

Here is the practical reality that catches GTA homeowners off guard: once the second side of a wall is boarded, the inspector cannot verify what's inside. The City of Toronto's standard inspection sequence for a basement finish or garage conversion requires a framing inspection after framing, insulation, vapour barrier, and any required fire-rated board on one side are complete — but before the other side is closed. If you skip the framing inspection and board both sides, the inspector has no way to confirm the correct assembly was used and will typically require you to open sections of the wall for verification. That means cutting out drywall you just installed and paid to finish.

The correct sequence is: rough-in work complete → call for framing/insulation inspection → inspector verifies fire-rated board, vapour barrier, insulation, and penetration fire-stopping → inspection passes → board the remaining side → call for drywall inspection if required → proceed to finishing.

Documentation and Product Substitution

Inspectors can also ask for product documentation — the manufacturer's cut sheet or ULC listing for the specific board used. This matters most when a contractor uses a less common product or a regional brand the inspector isn't familiar with. Keeping the board wrappers or taking photos of the board markings before installation is a simple precaution that eliminates any ambiguity. For complex assemblies in condos or multi-unit buildings, the project may require a ULC assembly number on the permit drawings, and the inspector will verify the installed assembly matches that number.

Practical Tips for Homeowners

Before your framing inspection, photograph the board markings on every fire-rated sheet installed. This takes five minutes and gives you permanent documentation that the correct material was used — useful if there's ever an insurance claim, a future sale, or a dispute with your contractor. Also confirm with your contractor that all penetrations through fire-rated assemblies are fire-stopped with ULC-listed caulking or putty pads — a single unsealed electrical box in a garage fire separation is a code deficiency that will fail the inspection.

If you're managing a basement finish or garage conversion in Toronto, the permit and inspection process is non-negotiable. The City of Toronto's building portal allows you to book inspections online, and turnaround times for residential framing inspections are typically two to five business days.

Need help finding a drywall contractor experienced with fire-rated assemblies and Toronto permit requirements? Toronto Drywall Installers can match you with local professionals through the Toronto Construction Network — or browse the directory directly at torontoconstructionnetwork.com/directory?trade=insulation.