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At a Glance
Why Choose This Product
Creates a bonded moisture barrier beneath tile and stone
Helps keep common shrinkage cracks from reaching the finished surface
Low 0.3 perm rating supports steam showers and wet rooms
Suitable for approved interior and exterior wall and floor installations
Conforms to approved wall and floor surfaces beneath tile
Meets ANSI A118.10 and A118.12 and is IAPMO listed
Product Information
GURU® Water-Stop Waterproofing Membrane creates a bonded moisture barrier beneath ceramic tile and natural stone while helping protect the finished surface from common in-plane shrinkage cracks. It meets ANSI A118.10 for waterproofing and ANSI A118.12 standard performance for crack isolation, combining two important forms of protection in one membrane.
With a low 0.3 perm rating, Water-Stop provides moisture protection for shower walls and floors, 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 where dependable waterproofing is required beneath tile or stone.
The flexible 20 mil multilayer sheet has non-woven fibers on both sides to support strong bonding beneath ceramic tile and natural stone. Designed for approved interior and exterior surfaces, Water-Stop provides a thin, adaptable tile waterproofing membrane for new construction, renovations, thin-bed installations, and thick-bed assemblies.
Product Resources
Common Questions
GURU Water-Stop is installed beneath ceramic tile and natural stone to provide bonded waterproofing and crack isolation. The flexible 20 mil sheet protects approved walls and floors from moisture penetration and helps keep common in-plane shrinkage cracks from transferring through to the finished tile or stone surface.
Yes. Water-Stop has a low 0.3 perm rating and is designed for showers, steam showers, wet rooms, tub surrounds, and other moisture-exposed tile installations. It can be used on approved wall and floor substrates in residential or commercial projects when incorporated into a properly completed waterproofing system.
The Water-Stop sheet passes ASTM D4068 waterproofness testing and meets ANSI A118.10. A complete waterproof assembly also requires properly treated seams, corners, penetrations, transitions, and drain connections. Those details must be sealed according to GURU instructions so water cannot bypass the membrane at connection points.
Water-Stop meets ANSI A118.12 standard performance requirements and isolates common in-plane shrinkage cracks from the finished tile surface. It should not be used over structural cracks, dynamic expansion joints, cracks wider than 1/8", or cracks with vertical differential movement. The substrate must remain within tile industry deflection limits.
Approved interior substrates include concrete, masonry, cement mortar beds, cement plaster, gypsum wallboard, exterior-glue plywood, existing ceramic tile or stone, cement terrazzo, cement backer board, and compatible gypsum or fiber-cement underlayments. Exterior substrates include suitable concrete, ceramic tile or stone, and cement terrazzo. Do not bond directly to particleboard, interior-glue plywood, or hardwood.
Water-Stop should be bonded with a modified thin-set mortar suitable for the substrate. GURU specifies mortars conforming to ANSI A118.4, A118.11, or A118.15, as applicable. Proper mortar selection, coverage, seam treatment, and curing are important to create a reliable bonded waterproofing assembly before tile is installed.
Water-Stop can connect to a shower drain with a suitable membrane clamping collar or an integrated bonding flange. The drain connection must be sealed according to the applicable GURU and drain manufacturer instructions. Proper treatment around the drain is necessary to maintain the continuous waterproofing layer beneath the tile assembly.
No. Water-Stop is a waterproofing sheet, not a sloped shower base. Shower floors must already have a properly prepared slope of at least 1/4" per foot, or 2%, toward the drain. The membrane is then bonded over that sloped surface to create the waterproof layer beneath tile.
