What is the correct drywall installation sequence for a Toronto bathroom with a walk-in shower and heated floors?

The correct sequence for Toronto bathroom drywall is: framing and rough-ins first, then heated floor system, waterproofing membrane, cement board in wet areas, regular moisture-resistant drywall elsewhere, followed by taping and finishing. This sequence ensures proper moisture protection and maintains the heated floor warranty.

The framing and mechanical rough-ins must be completed first — electrical for lights, fans, and heated floor controls, plumbing for the shower valve and any other fixtures, and HVAC for ventilation. In Toronto's humid summers, bathroom ventilation is critical to prevent mould growth behind drywall. The Ontario Building Code requires exhaust fans rated at minimum 50 CFM for bathrooms under 100 square feet.

Heated floor installation comes next, typically electric mat systems in Toronto bathrooms. The heating cables or mats are installed over the subfloor with the thermostat sensor wire run to the wall switch location. This must be completed and tested before any wall covering goes up, as accessing the system later requires tearing out finished surfaces. Most manufacturers void warranties if the system isn't tested before being covered.

Waterproofing is absolutely critical in Toronto's climate. Install a waterproof membrane (like RedGard or Kerdi) on all surfaces that will receive tile — shower walls, tub surrounds, and floor areas. This goes directly over the heated floor system and up the walls to the required height. Many Toronto contractors extend waterproofing 6 inches beyond shower areas as extra protection against GTA's high humidity levels.

For wall substrates, never use regular drywall in direct contact with water. Install cement board (Durock, HardieBacker, or similar) on shower walls and tub surrounds — this provides a stable, waterproof base for tile. Use moisture-resistant drywall (green board) or mould-resistant drywall (purple board) on other bathroom walls. Purple board with fiberglass facing is superior in Toronto's humid conditions as it eliminates the paper food source for mould entirely.

Installation specifics: Cement board should be installed with appropriate fasteners every 8 inches, with 1/4-inch gaps at all joints that get sealed with mesh tape and cement board compound. Leave a 1/4-inch gap between the cement board and shower pan or tub — this gets sealed with caulk, not compound. Moisture-resistant drywall on other walls follows standard installation — screws every 12 inches on ceilings, 16 inches on walls, minimum 3/8 inch from edges.

Taping and finishing follows standard procedures, but allow extra drying time in Toronto's humid summers. Use setting compound (hot mud) for the first coat if working during humid periods, as it sets by chemical reaction rather than air drying. All joints must be properly taped and finished to Level 4 standard before priming and painting.

Critical Toronto considerations: Install proper vapour barrier on exterior walls before drywall — Ontario Building Code requires 6-mil polyethylene on the warm side of insulation. Ensure bathroom exhaust fans vent directly outside, not into attics or soffits, as this causes moisture problems in Toronto's freeze-thaw climate. Many Toronto condos have restrictions on bathroom renovation hours and require dust containment during drywall work.

Professional installation is strongly recommended for bathroom drywall, especially around shower areas. Improper waterproofing or substrate installation leads to catastrophic water damage that's expensive to repair. The heated floor system adds complexity that most DIYers aren't equipped to handle properly.

Need help finding a drywall professional experienced with bathroom installations? Toronto Drywall Installers can match you with contractors familiar with heated floor systems and proper moisture protection techniques.