What should I budget for drywall work when finishing an above-garage bonus room in Markham?

Budget $6,000 to $15,000 for the drywall scope when finishing an above-garage bonus room in Markham, with most projects falling in the $8,000 to $12,000 range for a typical 300 to 500-square-foot space. This includes fire-rated drywall on the floor assembly, insulation, vapour barrier, wall and ceiling boarding, taping, and Level 4 finishing. The cost is higher than a standard room because of the fire separation, sound isolation, and insulation requirements that apply when converting space above a garage.

The fire separation between the bonus room and the garage below is the single biggest cost driver and a non-negotiable Ontario Building Code requirement. The floor/ceiling assembly separating the living space from the garage must achieve a minimum 45-minute fire resistance rating. This typically means 5/8-inch Type X fire-rated drywall on the garage ceiling below (if not already present), and the floor assembly itself must incorporate fire-rated materials. On the bonus room side, the walls and ceiling receive standard drywall, but any wall that shares a boundary with the garage below or to the side also requires Type X board. Fire-rated assemblies cost $3.50 to $6.00 per square foot installed, compared to $2.50 to $4.00 for standard wall board.

Insulation is critical in an above-garage bonus room and directly affects your drywall budget because it must be installed and inspected before any drywall goes up. The floor over the garage requires insulation to a minimum of R-31 (Ontario Building Code for floors over unheated spaces), and exterior walls need R-24. The knee walls — the short angled walls that follow the roofline in rooms with cathedral or vaulted ceilings — require careful insulation and a continuous 6-mil polyethylene vapour barrier on the warm side. Improperly insulated knee walls are the most common cause of comfort complaints and moisture problems in above-garage bonus rooms across Markham and the GTA. Insulation and vapour barrier installation for a bonus room typically costs $1,500 to $3,500, and this work must be completed before the drywall crew arrives.

The ceiling geometry in a bonus room significantly affects drywall costs. If the room has a flat ceiling with standard 8-foot or 9-foot height, the drywall installation is straightforward. However, many above-garage bonus rooms in Markham subdivision homes have vaulted or cathedral ceilings that follow the roofline, creating angled surfaces that are more difficult and time-consuming to board and finish. Angled ceiling drywall adds approximately 20 to 30% to the hanging and finishing cost compared to flat ceilings, because sheets must be cut to follow the slope, joints along the angle require extra compound and sanding, and working at height on angled surfaces is slower and more physically demanding. A vaulted ceiling bonus room can push the total drywall cost to the higher end of the $8,000 to $15,000 range.

Sound isolation between the bonus room and the garage is worth the investment, even though it is not always code-required for a room above your own garage (it is required if the garage is shared or if the space is being converted to a secondary suite). Road noise, garage door openers, car engines, and workshop noise all transmit directly through the floor assembly. Installing resilient channel on the bonus room ceiling ($1.50 to $2.50 per linear foot) and using sound insulation batts in the floor cavity adds $1,000 to $2,500 to the project but makes the room genuinely comfortable as a bedroom, home office, or media room.

A building permit is required for finishing a bonus room above a garage in Markham. The project involves changes to the building's use and occupancy, fire separations, insulation, electrical, and potentially HVAC — all of which require permits and inspections. The framing and insulation inspection must be passed before any drywall is installed. Your drywall contractor should be coordinated with the electrician and HVAC installer to ensure all rough-in work is complete and inspected before boarding begins.

For the complete bonus room renovation — including framing, insulation, electrical, HVAC extension, drywall, flooring, and painting — budget $20,000 to $45,000 in the Markham market. The drywall scope represents roughly 30 to 40% of the total project cost. Get matched with a drywall contractor for a free estimate through Toronto Drywall Installers.