There are two methods to seal KERDI-BOARD to a bathtub. Please refer to the Schluter™-Shower System Installation Handbook for complete details and installation instructions.
When the KERDI-BOARD is installed over the lip of the tub
Leave a 1/4″ (6 mm) gap between the KERDI-BOARD and the tub deck. Place painter’s tape to protect the tub deck. Completely fill the gap between the KERDI-BOARD and tub using Schluter™-KERDI-FIX or other suitable sealant. Apply Schluter SET™ , ALL-SET™ , FAST-SET™ or unmodified thin-set mortar to the KERDI-BOARD using a ¼" x 3/16" (6 mm x 5 mm) V-notched trowel or the Schluter™-KERDI-TROWEL. Apply KERDI-BAND waterproofing strips or 5" (125 mm)-wide cut sections of KERDI waterproofing membrane. Solidly embed the membrane in the mortar and KERDI-FIX to ensure full coverage and remove air pockets.
When the KERDI-BOARD is installed flush with the lip of the tub
Apply KERDI-FIX or other suitable sealant to the lip of the tub and spread using a small notched trowel. Apply Schluter SET™ , ALL-SET™ , FAST-SET™ or unmodified thin-set mortar to the KERDI-BOARD using a ¼" x 3/16" (6 mm x 5 mm) V-notched trowel or the KERDI-TROWEL. Apply KERDI-BAND waterproofing strips or 5" (125 mm)-wide cut sections of KERDI waterproofing membrane. Solidly embed the membrane in the mortar and KERDI-FIX to ensure full coverage and remove air pockets.