Who is responsible for waterproofing in a condo bathroom — the unit owner or the condo corporation?

In almost all Toronto condos, the unit owner is responsible for waterproofing within their bathroom during a renovation, while the condo corporation is responsible for the building's original waterproofing systems and shared structural elements. The specific division of responsibility depends on your condo's declaration, which defines the boundary between the unit and the common elements — but in practical terms, if you are renovating your bathroom, the waterproofing behind your new tile, under your shower base, and around your fixtures is your responsibility and your cost.

The condo declaration typically defines your unit as everything from the interior surface of the concrete slab and walls inward. This means the drywall, backer board, waterproof membrane, tile, fixtures, and all finishes within your bathroom are your property and your maintenance responsibility. The concrete structure itself — the slab between floors, the structural walls, and the plumbing stack — is a common element maintained by the corporation.

Why This Matters for Your Renovation

When you renovate your condo bathroom in Toronto, you are taking on the obligation to install proper waterproofing that protects not just your unit but the units and common areas below you. If your shower waterproofing fails and water leaks through the slab into the unit below, you are liable for the damage — both under the Condominium Act and through your personal condo insurance policy. This is one of the most important reasons to hire experienced professionals for condo bathroom waterproofing rather than cutting corners.

The Ontario Building Code requires a continuous waterproof membrane behind all shower and tub surrounds. In a condo, this requirement carries extra weight because a failure does not just damage your own home — it damages someone else's. Your waterproofing system should include a sheet membrane (such as Schluter Kerdi) or liquid-applied membrane (such as RedGard or Mapei AquaDefense) covering the entire shower area from the base to at least 6 inches above the showerhead rough-in. The shower floor must have a waterproof pan membrane that directs any water that penetrates the tile and grout to the drain.

Insurance Implications

Every condo owner in Ontario should carry unit owner insurance (often called an HO-6 policy) that includes coverage for improvements and betterments — this covers your renovated bathroom, including fixtures, finishes, and installed materials. Critically, your policy should also include personal liability coverage and coverage for damage to other units caused by your unit, including water damage from a bathroom leak.

Before starting a condo bathroom renovation, review your insurance policy and consider increasing your improvements and betterments coverage to reflect the value of the renovation. A $25,000 to $40,000 bathroom renovation should be covered by your policy. Many Toronto condo corporations also carry a master policy with a deductible that can be charged back to the unit owner who caused the damage — these deductibles can range from $10,000 to $50,000 in GTA condo buildings.

Practical Steps

Before demolishing your existing bathroom, document the current condition with photos and video, including the condition of the subfloor and any visible waterproofing. During the renovation, have your contractor document the waterproofing installation with detailed photos showing complete membrane coverage, sealed seams, and proper integration with the drain. These records protect you if a future leak is attributed to your renovation. Ensure your contractor provides a written warranty on the waterproofing installation — reputable GTA bathroom renovation contractors typically warranty their waterproofing work for 5 to 10 years.