What extra waterproofing steps are needed when renovating a bathroom in a leaky condo era building in BC?

Renovating a bathroom in a leaky condo era building (roughly 1985-1999) in BC requires waterproofing measures that go well beyond standard bathroom renovation practice — you need to address the existing moisture damage, prevent interior moisture from reaching already-compromised wall cavities, and create a bathroom that can withstand Metro Vancouver's relentless humidity for decades. Standard waterproofing that would be adequate in a newer, properly enveloped building is not sufficient in these structures.

The fundamental problem with leaky condo era buildings is that the building envelope allows moisture in from the outside. In a properly built building, the wall cavity behind your bathroom stays dry, and your waterproofing only needs to keep shower water from reaching the wall structure. In a leaky condo, the wall cavity may already contain moisture from exterior leaks, and your bathroom waterproofing must prevent interior moisture from adding to an already-wet condition while also creating a durable, long-lasting wet area finish.

Full-Perimeter Waterproofing

Standard practice in a newer building is to waterproof the shower enclosure — shower walls and shower floor. In a leaky condo era building, waterproof the entire bathroom. This means applying waterproofing membrane to the complete bathroom floor with the membrane turned up all walls at least 6 inches (150 mm), waterproofing all shower and tub walls from floor to ceiling, and treating every penetration (plumbing pipes, drain connections, valve bodies, shower niche) with waterproofing detail components.

For the shower area, Schluter Kerdi sheet membrane is the gold standard — it provides a consistent, reliable waterproof barrier at $8 to $15 per square foot installed. For the bathroom floor outside the shower, a liquid-applied membrane like RedGard or Laticrete Hydroban at $5 to $10 per square foot installed is effective and more practical to apply around toilets, vanities, and other obstructions. The critical requirement is continuity — every seam, corner, and penetration must be properly treated with compatible seam tape or band to create an unbroken waterproof envelope.

Pre-slope the shower floor before waterproofing. The substrate beneath the waterproof membrane must slope toward the drain at a minimum of 1/4 inch per foot. In leaky condo era buildings, the existing subfloor may have irregularities from settling or moisture damage. A mortar bed or Schluter Kerdi-Shower-ST tray system creates the proper slope and provides a reliable substrate for the membrane.

Substrate Preparation

Remove all existing moisture-damaged materials before applying new waterproofing. This means taking walls back to studs and the floor back to subfloor. Inspect every piece of framing for rot, mould, and structural integrity. Replace any compromised framing members — in leaky condo era bathrooms, the bottom plate of walls and the subfloor around drains are the most common areas of deterioration. Treat remaining framing with antimicrobial solution and allow it to dry completely before closing the walls.

Use cement backer board exclusively for all tile substrates — Durock, HardieBacker, or equivalent. Never use standard drywall or moisture-resistant greenboard in any location where tile will be installed. In a leaky condo building, cement backer board should extend to all bathroom walls, not just the shower area, because the ambient moisture levels in these buildings are higher than normal.

Vapour Barrier Strategy

In leaky condo era buildings, the vapour barrier situation is often compromised or incorrectly installed. Your renovation contractor should assess the existing vapour barrier on exterior walls and correct any deficiencies. The vapour barrier must be on the warm side of the insulation (interior side in Metro Vancouver) and must be continuous. Where your waterproofing membrane overlaps with the vapour barrier location, ensure the two systems work together rather than creating a moisture trap between layers.

Ventilation — Non-Negotiable

Install the most powerful exhaust fan practical — minimum 80 CFM, ideally 110 CFM for a standard bathroom. In a leaky condo building, removing interior moisture quickly is even more critical because the wall cavities have limited drying capacity. A humidity-sensing fan that runs automatically when humidity rises and continues running until levels drop is ideal for these buildings. The fan must duct to the exterior — verify the existing duct path is clear and properly connected, as disconnected exhaust ducts dumping moisture into ceiling cavities are a common problem in leaky condo era buildings.

Budget for these enhanced waterproofing measures. Full bathroom waterproofing with membrane, proper substrate preparation, backer board on all walls, and upgraded ventilation typically adds $3,000 to $8,000 compared to a standard bathroom renovation. For a mid-range bathroom renovation in a leaky condo era building in Metro Vancouver, expect total costs of $25,000 to $45,000 including the enhanced moisture protection. This investment protects your unit, your neighbours' units, and ensures your new bathroom lasts 15 to 25 years rather than failing in 3 to 5.