Can I use drywall in a Vancouver bathroom or should I always use moisture-resistant board?

You can use moisture-resistant drywall (greenboard) on bathroom walls and ceilings that are NOT inside shower or tub enclosures, but you should never use standard drywall anywhere in a Vancouver bathroom, and you must use cement backer board behind all tile in wet areas. This distinction is critical in Metro Vancouver's climate, where outdoor humidity averaging 75-85% year-round means bathrooms take much longer to dry out between uses than in drier parts of Canada.

Standard drywall has a paper facing that absorbs moisture and becomes a food source for mould. In Vancouver's marine climate, where ambient humidity is already high and homes receive over 1,200 millimetres of rainfall annually, standard drywall in a bathroom will develop mould growth on the surface and inside the wall cavity far faster than it would in a prairie city like Calgary. Even in areas that don't get directly splashed — the ceiling above the shower, the wall behind the toilet, the area above the vanity — standard drywall is a poor choice for any Vancouver bathroom.

Moisture-resistant drywall (greenboard) has a wax-treated paper facing and a moisture-resistant core that performs well in humid environments. It's appropriate for bathroom walls and ceilings that are outside the shower and tub wet zone — areas like the wall behind the toilet, the wall opposite the shower, and the bathroom ceiling (provided you have proper ventilation). In Metro Vancouver, greenboard typically costs $14-$20 per sheet compared to $10-$14 for standard drywall, making the upgrade modest relative to the protection it provides. For ceilings in particularly humid bathrooms, mould-resistant drywall (purple board) with fibreglass facing instead of paper is an even better choice at $18-$28 per sheet.

Cement backer board is mandatory behind all tile in wet areas. The BC Building Code requires waterproofing in shower and tub enclosures, and the substrate behind that waterproofing membrane must be dimensionally stable when exposed to moisture. Products like Durock, HardieBacker, or Kerdi-Board are the only acceptable substrates for tile in shower walls, tub surrounds, and shower floors. Cement backer board costs $10-$18 per sheet and adds roughly $300-$600 to a typical shower installation — a small fraction of the total project cost. On top of the backer board, a waterproofing membrane such as Schluter Kerdi ($4-$8 per square foot for material) or a liquid-applied membrane like RedGard ($2-$5 per square foot) must be applied before any tile goes up.

The consequences of using the wrong material are severe in Vancouver's climate. If standard drywall or greenboard is used behind shower tile, moisture migrates through grout joints and penetrations, saturates the drywall core, and creates ideal conditions for mould growth. Because Vancouver's humidity prevents the wall cavity from drying naturally, mould colonies can establish within weeks and spread aggressively behind the tile where you cannot see them. Within 2-3 years, the drywall deteriorates, tiles loosen, and the entire shower must be torn out and rebuilt — typically costing $8,000-$15,000, which is two to three times what a proper installation would have cost originally.

For condo and strata bathroom renovations, many strata corporations now specifically require cement backer board and documented waterproofing in their renovation approval process. This protects both the unit owner and neighbouring units from water damage. If you're planning a bathroom renovation, confirm your strata's specific requirements before selecting materials.

A practical rule for any Vancouver bathroom renovation: greenboard or purple board on walls and ceilings outside the wet zone, cement backer board with waterproofing membrane behind all tile in the shower and tub surround, and proper mechanical ventilation (minimum 50 CFM exhaust fan, ideally 80-110 CFM) to manage moisture throughout the space.