What is the cost to install fire-rated drywall for a legal basement apartment in the GTA?

Installing fire-rated drywall for a legal basement apartment in the GTA costs between $8,000 and $20,000 for the complete fire separation assembly, including materials, labour, fire caulking, and finishing. The drywall materials alone run $3,000 to $6,000, with professional installation, taping, mudding, and finishing making up the balance.

The Ontario Building Code requires a 1-hour fire-rated separation between a secondary suite and the rest of the dwelling. For the ceiling — the most critical element, since fire and smoke rise — this means installing two layers of 5/8-inch Type X fire-rated drywall. Each sheet of 5/8-inch Type X drywall costs $24 to $35 per 4x8 sheet (compared to $15 to $22 for standard 1/2-inch drywall), and you need two layers for the full ceiling area. For a typical 800-square-foot basement ceiling, that is approximately 50 sheets per layer, or 100 sheets total — $2,400 to $3,500 in ceiling drywall materials alone.

The walls separating the suite from the rest of the house also need fire-rated drywall, though typically only one layer of 5/8-inch Type X is required on shared walls (check with your building inspector, as requirements can vary based on the wall assembly). Exterior-facing basement walls that are not shared with another unit can use standard 1/2-inch drywall. The cost for fire-rated drywall on separating walls adds $500 to $2,000 depending on how many walls are shared.

Beyond the drywall itself, achieving a true 1-hour fire rating requires meticulous attention to penetrations and joints. Every location where a pipe, wire, duct, or other building element passes through the fire-rated assembly must be sealed with intumescent fire caulking or fire-rated putty pads. In a typical basement, there are dozens of these penetrations — electrical wires, plumbing pipes, HVAC ducts, gas lines, and structural connections. Fire caulking materials cost $10 to $25 per tube, and a complete basement fire separation may require 10 to 30 tubes plus professional labour to apply them correctly. Fire dampers must be installed in any HVAC ductwork that crosses the fire separation, at $200 to $500 per damper — most homes need 4 to 8 fire dampers.

Fire-rated doors are required at every entrance to the suite. A 20-minute fire-rated door with self-closing hardware costs $300 to $800 per door installed. The self-closing hardware is a code requirement — the door must close automatically to maintain the fire separation if a fire occurs.

The installation labour for fire-rated drywall is more expensive than standard drywall for several reasons. Two-layer ceiling installation is physically demanding and time-consuming — each sheet of 5/8-inch drywall weighs approximately 70 pounds, and lifting and securing them overhead requires experienced drywall crews. The second layer must be installed with screws offset from the first layer's seams to maintain the fire rating. Taping, mudding, and finishing two-layer ceilings takes more time because the surface must be perfectly smooth for painting. Installation labour for the complete fire-rated assembly runs $3 to $6 per square foot of wall and ceiling area.

City of Toronto building inspectors will verify the fire separation during the rough-in inspection and final inspection. They check for proper drywall type and thickness (the Type X designation is stamped on every sheet), correct screw spacing and penetration, fire caulking at all penetrations, fire dampers in ductwork, and fire-rated doors with self-closers. Failing the fire separation inspection is one of the most common reasons for secondary suite permit delays — getting it right the first time with an experienced contractor saves weeks of rework.