Most people assume a bathtub surround is automatically waterproof — the tub is a big waterproof pan, so surely the walls above it are fine, right? They're not. Standard cement board or drywall behind tile in a tub surround gets wet, stays wet, and eventually fails. The Schluter KERDI-TUBKIT is the fix: a complete waterproofing kit for tiled bathtub surrounds that creates a bonded, sealed membrane behind every inch of tile.

The KERDI-TUBKIT contains all the KERDI waterproofing components needed to waterproof the wall assembly above a standard bathtub: KERDI membrane, KERDI-BAND strips for seams and corners, KERDI-SEAL pipe seals for faucet/spout penetrations, and KERDI-FIX sealant. It covers 7 square meters (approximately 75 sq ft) of wall surface — enough for a standard three-wall tub surround.

Why your tub surround needs this

Cement board doesn't stop water. Neither does standard drywall. They're "moisture-resistant," which is a fancy way of saying "it takes longer to rot." KERDI is a bonded waterproof membrane — water hits it, stops, and runs down to the tub. No seepage through the wall, no wet framing, no mold you can't see. This is the professional standard for tile over tub installation.

What's included

• KERDI membrane — enough to cover a standard three-wall surround
• KERDI-BAND — waterproofing strips for seams between panels, floor-to-wall joints, and inside corners
• KERDI-SEAL pipe seal(s) — for showerhead and tub spout penetrations
• KERDI-FIX — flexible sealant for bonding membrane to non-mortar surfaces and sealing around faucet valves

What it pairs with

• Substrate: KERDI-BOARD panels replace cement board — lighter, actually waterproof, tile same day
• Setting mortar: Schluter SET (unmodified) or ALL-SET (for wood-framed walls)
• Corner profile: JOLLY or RONDEC at outside corners where surround meets open wall or window

Pro Tips

• Always install KERDI-BAND at the tub deck-to-wall transition — that joint is where most tub surround failures start. Run KERDI-BAND across the tub flange and up the wall before applying full KERDI membrane
• Seal every pipe penetration with KERDI-SEAL or KERDI-FIX before tiling — even a small gap around a faucet handle is a water highway straight to the framing
• Use silicone caulk (not grout) at the tub-to-tile joint at the tub deck — grout cracks when the tub flexes. Silicone moves with it
• The KERDI membrane only needs 1/8" × 1/8" square-notch trowel to bond — don't use a big trowel or you'll press air bubbles in

This kit comes with a 10-year warranty as part of the Schluter system. A tub surround done right shouldn't need attention for decades. This is how you do it right.