What is a shower pan liner?

A shower pan liner is a waterproof membrane installed beneath the shower floor to create a watertight barrier that prevents water from seeping into the subfloor and surrounding structure. It's essentially the foundation of your shower's waterproofing system, working as a backup protection layer even if water penetrates through the tile and grout above.

The liner is typically made from PVC, CPE (chlorinated polyethylene), or rubber membrane materials and must be installed in a specific layered system. In Ontario, the liner sits on top of a pre-slope (the first layer of mortar bed), extends up the walls at least 6 inches above the shower threshold, and connects to the shower drain assembly. A second mortar bed is then poured over the liner to create the final slope toward the drain, followed by tile installation.

Proper installation is critical because any punctures, improper seams, or inadequate wall height can lead to water damage behind your shower walls or below the bathroom floor. The Ontario Building Code requires specific waterproofing standards for shower installations, and in Ottawa's climate with freeze-thaw cycles, water intrusion can cause significant structural damage over time.

Modern shower installations often use liquid-applied membranes or sheet membranes like Schluter systems as alternatives to traditional pan liners. These newer systems can be easier to install properly and may offer better long-term performance. The key is ensuring whatever waterproofing system is used meets code requirements and is installed by someone experienced with proper techniques.

For shower renovations in Ottawa, having a licensed contractor handle the waterproofing ensures the work meets Ontario Building Code standards and protects your investment. Want to discuss waterproofing options for your shower project? We offer free consultations to review your specific situation.