Recommended Add-Ons
At a Glance
Why Choose This Product
Protects approved tile and stone assemblies from moisture penetration.
Helps keep limited in-plane shrinkage cracks from transferring to the finished surface.
A 0.3 perm rating supports steam showers and other wet areas.
Adapts to approved wall and floor substrates with minimal buildup.
Fits approved residential and commercial applications.
Meets ANSI A118.10 and ANSI A118.12 standard-performance requirements and is IAPMO listed.
Product Information
GURU Water-Stop Waterproofing Membrane creates a flexible moisture barrier beneath ceramic tile and natural stone while helping protect the finished surface from limited in-plane cracks. It meets ANSI A118.10 for waterproofing and ANSI A118.12 standard performance for crack isolation.
With a 0.3 perm rating, Water-Stop supports showers, steam showers, wet rooms, tub surrounds, bathrooms, kitchens, backsplashes, pool surrounds, and balconies. It is suitable for approved residential and commercial wall and floor applications.
The multilayer sheet conforms to approved interior and exterior substrates while keeping the assembly thin. Its nonwoven faces support bonding with compatible modified thin-set mortar, helping create a continuous waterproofing layer when seams and transitions are properly sealed.
Product Resources
Common Questions
Water-Stop is bonded beneath ceramic tile and natural stone to waterproof approved walls and floors. It also provides standard-performance crack isolation, helping protect finished surfaces from limited in-plane shrinkage cracks in residential and commercial installations.
Yes. Its 0.3 perm rating supports showers, steam showers, wet rooms, tub surrounds, bathrooms, kitchens, backsplashes, pool surrounds, and balconies. Install it over an approved substrate as part of a fully sealed wall or floor system.
The sheet meets ANSI A118.10 for bonded waterproofing. Complete protection depends on correctly sealing seams, corners, transitions, penetrations, and drain connections so moisture cannot bypass the membrane. Follow GURU's current installation requirements for each detail.
Water-Stop meets ANSI A118.12 standard performance for limited in-plane shrinkage cracks. It is not intended for structural cracks, dynamic expansion joints, cracks wider than 1/8", or cracks with vertical differential movement.
Approved substrates include concrete, masonry, mortar beds, cement plaster, gypsum wallboard, exterior-glue plywood, existing tile or stone, terrazzo, cement backer board, and compatible underlayments. Do not bond directly to particleboard, interior-glue plywood, or hardwood.
Use a modified thin-set mortar appropriate for the substrate and meeting ANSI A118.4, A118.11, or A118.15 as applicable. Follow GURU requirements for mortar coverage, seam treatment, penetrations, and curing.
Use a compatible drain with a membrane clamping collar or integrated bonding flange. Water-Stop does not create slope, so shower floors must be prepared at least 1/4" per foot, or 2%, toward the drain before installation.
Available formats include 26, 32, and 43 sq. ft. sheets plus 54, 108, 323, and 430 sq. ft. rolls. Select the format that best fits the installation while minimizing seams and material waste.
