Schluter®-KERDI Waterproofing and Vapor-Retardant Membrane

KERDI is the waterproofing membrane that changed how tile showers get built in North America. Before KERDI, "waterproofing" meant cement board (which is moisture-resistant, not waterproof) and a lot of hope. KERDI is a true bonded waterproofing membrane — nothing gets through it, and it carries a 10-year system warranty when used with the full Schluter shower system.

The membrane is a pliable polyethylene (PEVA) core with non-woven polypropylene fleece laminated to both sides. The fleece anchors into thin-set mortar the same way tile does — press it in, comb it down, tile over it. No liquid membrane, no drying time, no multiple coats. One layer, fully bonded, done.

What KERDI actually does

• Waterproofing: Passes ANSI A118.10 bonded waterproof membrane standards — water simply does not pass through
• Vapor retarder: Controls moisture vapor movement through the assembly, preventing condensation damage behind the tile
• Limited crack bridging: Accommodates minor substrate movement without breaking the waterproof seal
• Tile-ready surface: Tile bonds directly to KERDI — no additional skim coat or primer needed

Where to use KERDI

• Shower walls — over studs with KERDI-BOARD, or directly over concrete, masonry, or cement board
• Shower floors — over mortar beds or KERDI-SHOWER prefab trays
• Tub surrounds and wet areas anywhere tile is going over a potentially damp surface
• NOT for exterior use — interior wet areas only

Installation overview

Apply SET or ALL-SET mortar with a 1/4" × 3/16" V-notched trowel (or the Schluter KERDI-TROWEL). Press KERDI fleece-side into the mortar, working out air pockets. Seams need a 2" minimum overlap, embedded in mortar. All inside corners and floor-wall transitions need KERDI-BAND — don't skip this step. Pipe penetrations get sealed with KERDI-SEAL-PS or KERDI-FIX. Once the mortar cures, tile directly on the KERDI surface.

Pro tips

• Use the KERDI-TROWEL for the membrane install — its 1/8" × 1/8" square-notch profile is optimized for full KERDI embedment without over-applying mortar
• Pre-cut KERDI-KERECK-F corner pieces for outside corners — trying to fold and miter KERDI at outside corners is a pain; the pre-formed pieces are cleaner and more reliable
• Always KERDI-BAND floor-wall transitions even if you've already applied full KERDI to the wall — the floor-wall junction is the highest-movement area in the assembly
• Test with water before tiling: Once your waterproofing is done and cured, fill the shower floor with water and let it sit 24 hours before tiling. Easier to fix a problem now than after the tile is down

KERDI vs. other waterproofing methods

Liquid-applied membranes (like RedGard) require multiple coats, precise wet film thickness, and significant dry time. A pinhole means a leak. KERDI is a sheet membrane — the waterproofing is inherent in the material, not applied technique. The Schluter system is also warranted as a complete assembly — which liquid membranes typically aren't when used with third-party drains and setting materials.

Available in standard 3'3" (1m) wide rolls. Wide-format 6'7" (2m) rolls available for faster coverage with fewer seams on larger walls.