What is the correct order of operations for drywall installation when finishing a Toronto basement with a bathroom?

The correct order of operations for a Toronto basement finish with a bathroom is: rough-in trades first, then insulation and vapour barrier, then drywall hanging (ceilings before walls), then taping and finishing, and finally trim and paint — but the bathroom adds several critical sequencing steps that must happen at exactly the right time to avoid costly rework. Getting this sequence wrong is one of the most common mistakes in GTA basement renovations and can result in failed inspections, water damage, and thousands of dollars in rework.

Before Any Drywall Goes Up

Rough-in plumbing for the bathroom must be completed and inspected first. This includes the drain lines, water supply lines, shower/tub rough-in, and toilet flange. In Toronto basements, the plumbing rough-in often requires breaking into the concrete slab for drain lines, which must be done well before any framing or drywall work begins. Rough-in electrical comes next or concurrently — all wiring for outlets, switches, lighting, bathroom exhaust fan, and any dedicated circuits (GFCI-protected outlets are required in bathrooms by the Ontario Electrical Safety Code). If you are adding HVAC duct extensions to the basement, those runs also need to be in place before insulation.

All rough-in work must pass municipal inspection before you close up the walls. In Toronto, this means booking an inspection with the City of Toronto Building Division — and you must have your building permit posted on site. The inspector needs to see the framing, plumbing, electrical, and HVAC rough-ins before any insulation or drywall conceals them. Drywalling before the rough-in inspection is a permit violation and will require you to remove the drywall for inspection at your own expense.

After the rough-in inspection passes, install insulation in all exterior walls — minimum R-20 for below-grade basement walls per Ontario Building Code. Then install the 6-mil polyethylene vapour barrier on the warm (interior) side of all insulated walls, with all seams overlapped by at least 6 inches and taped with red Tuck tape. The vapour barrier must be continuous and sealed around all penetrations (electrical boxes, plumbing pipes) with acoustical sealant or vapour barrier tape.

Drywall Hanging Sequence

Hang ceilings first, then walls. This is a fundamental rule in drywall installation — the wall sheets butt up against the ceiling sheets, supporting the ceiling edge and creating a stronger assembly. In the bathroom specifically, use moisture-resistant drywall (green board at $20–$28 per sheet) or mould-resistant drywall (purple board at $24–$32 per sheet) on all walls and the ceiling. Standard drywall should never be used in a bathroom — the humidity from showers will cause it to deteriorate and grow mould.

Critical bathroom exception: do NOT install drywall inside the shower or tub surround area. The walls behind the shower tile or tub surround must be cement board (Durock, HardieBacker) — never drywall or green board. Cement board is not affected by direct water contact and provides a proper substrate for tile. Install cement board from the tub lip or shower pan to at least 6 inches above the showerhead height. The cement board joins the moisture-resistant drywall above the shower area.

In the main basement area outside the bathroom, standard 1/2-inch drywall is used on walls ($14–$20 per sheet) and 5/8-inch on ceilings ($18–$26 per sheet) to resist sagging between joists. Use 5/8-inch Type X fire-rated drywall ($20–$28 per sheet) on the ceiling of any area below a garage and on walls separating the furnace/utility room from living space.

After Drywall Is Hung

Taping and finishing proceeds in the standard sequence: first coat (bedding tape and filling screw heads), second coat (covering and feathering), and third coat (final skim and feathering to a Level 4 finish). Allow adequate drying time between coats — in a Toronto basement during winter, this can take 24–48 hours per coat because basements are naturally cool and humid. Running a dehumidifier and space heater speeds drying significantly.

After the final sanding and before paint, apply PVA drywall primer to seal the surface evenly. Then apply finish paint — in the bathroom, use a mould-resistant bathroom paint with a semi-gloss or satin finish for moisture resistance.

A complete basement finish with bathroom in the GTA (800–1,200 square feet) runs $25,000–$60,000 all-in, with the drywall scope alone typically costing $5,000–$12,000. This is a permit-required, multi-trade project that requires careful coordination. Get matched with experienced basement drywall professionals through Toronto Drywall Installers for a free estimate.