How much does it cost to install underfloor plywood sheeting before tile in a Vancouver bathroom reno?

Installing underfloor plywood sheeting before tile in a Vancouver bathroom renovation costs $4 to $10 per sq ft for the plywood substrate, plus an additional $3 to $6 per sq ft for the cement backer board that goes on top, bringing the total subfloor preparation to $7 to $16 per sq ft before any tile is laid. For a typical Vancouver bathroom of 50 to 80 sq ft, that means $350 to $1,280 for the subfloor system alone.

Let me break down what this work actually involves and why it matters so much in Metro Vancouver's wet climate. The plywood substrate serves as the structural base for your tile floor. In most Vancouver homes, the existing subfloor is either 5/8-inch or 3/4-inch plywood or OSB (oriented strand board) spanning floor joists at 16 inches on centre. For tile installation, this subfloor must be at minimum 1-1/8 inches thick to prevent deflection, which causes grout cracking and tile popping. If your existing subfloor is only 5/8 inch, a second layer of 1/2-inch or 5/8-inch exterior-grade plywood must be screwed and glued on top to reach the required thickness.

The plywood itself costs $1.50 to $3.00 per sq ft for 1/2-inch or 5/8-inch exterior-grade CDX or better. Installation labour runs $2.50 to $5.00 per sq ft because the sheets must be cut to fit, staggered so seams do not align with the subfloor below, and fastened with screws every 6 inches along joists and 8 inches in the field. Construction adhesive between layers is recommended. This is precision work because any movement or flex in the plywood assembly will crack grout lines within months.

On top of the plywood goes cement backer board, which is the critical layer between wood and tile. Cement board (Durock, HardieBacker, or similar) provides a rigid, moisture-resistant surface for thinset adhesion. Backer board costs $1.00 to $2.00 per sq ft for materials and $2.00 to $4.00 per sq ft for installation, which includes cutting, fastening with cement board screws, and taping and mudding all seams with alkali-resistant mesh tape and thinset.

Waterproofing in Vancouver's Climate

In a Vancouver bathroom, waterproofing over the backer board is not optional. The BC Building Code and industry best practices require a waterproofing membrane in all wet areas. A liquid-applied membrane like RedGard or Hydroban costs $0.75 to $1.50 per sq ft for materials and application. A sheet membrane like Schluter DITRA or Schluter Kerdi costs $2.00 to $4.00 per sq ft but provides both waterproofing and crack isolation in one layer. Given Metro Vancouver's persistent humidity, heavy rainfall, and the fact that bathroom moisture can migrate through concrete and wood structures for hours after use, a quality waterproofing membrane prevents rot, mould, and structural damage to the subfloor you just invested in.

There are additional costs that arise during subfloor preparation. If the existing subfloor has water damage or rot, which is extremely common in Vancouver bathrooms where previous renovations skipped proper waterproofing, damaged sections must be cut out and replaced. This discovery work adds $300 to $1,500 depending on the extent. Checking the joists beneath for rot or mould is also critical and occasionally reveals structural issues that require sistering or reinforcement.

Floor height is another consideration. Adding plywood, backer board, waterproofing, thinset, and tile can raise the finished floor height by 1 to 1-3/4 inches. This affects toilet flange height, door clearance, and transitions to adjacent rooms. Raising or replacing the toilet flange costs $150 to $300, and trimming doors costs $50 to $100 each. These are commonly overlooked line items that add up.

For a 60 sq ft Vancouver bathroom, a realistic all-in budget for subfloor preparation including plywood overlay, backer board, waterproofing membrane, and minor repairs is $600 to $1,000 before tile installation begins. This is the foundation that determines whether your tile floor lasts 5 years or 25 years. If you are planning a bathroom renovation, Vancouver Floor Installers can match you with experienced tile professionals who handle the complete subfloor-to-finish package.

---

Find a Flooring Contractor

Vancouver Floor Installers connects you with experienced contractors through the https://vancouverconstructionnetwork.com:

• SteelEdge Reinforcing Ltd. ✓
• Good Old Wood ✓
• True North Strong Contracting Ltd ✓