Products : Surface Prep : Waterproofing Membranes & Underlayments : Crack Buster® Pro Crack Prevention Mat Underlayment

Crack Buster® Pro Crack Prevention Mat Underlayment

A self-bonding, fabric reinforced, asphaltic membrane that isolates ceramic and natural stone tile from cracks in the substrate. Suitable for both full and partial coverage applications. CrackBuster Pro is a crack isolation membrane that meets the requirements of ANSI A118.12 and protects tile from in plane movement up to 3/8” (9.5 mm). Its strong self-adhesive backing and uniquely designed surface provide secure bonding for all types of ceramic, natural stone and terrazzo tile. CrackBuster Pro also helps reduce sound transmission through the tile assembly.

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Key Features

  • Rated for extra heavy duty applications
  • Easy application - Peel & stick
  • Elastomeric - Reduces crack transmission in tile and stone floors
  • Provides IIC sound reduction up to 18 dB
  • Reduces downtime allowing immediate installation of tile


  • Extra heavy-duty rating for installation within diverse substrates.
  • Exceeds ANSI A118.12 standards for crack isolation material.
  • Eliminates crack transmission in tile and stone floors.
  • Easy and quick self-adhesive installation reduces downtime for tile and stone installation.
  • Sound transmission reduction (11C) using A118.13 section 5.3 is 18 dB


Applicable Standards

American National Standards Institute (ANSI) ANSI A108.01, A108.17, A118.12 and A118.13 American National Standards for the Installation of Ceramic Tile ASTM International (ASTM)

  • ASTM C627 Standard Test Method for Evaluating Ceramic Floor Tile Installation Systems Using the Robinson-Type Floor Tester
  • ASTM D638 Standard Test Method for Tensile Properties of Plastics

Tile Council of North America (TCNA) TCNA Handbook for Ceramic Tile Installation, TCNA Method EJ171, F125 & F125A

Conformance to Building Codes

Installation must comply with the requirements of all applicable local, state and federal code jurisdictions.

Composition of Product

Crack Buster® Pro is an elastomeric, fabric-reinforced mat underlayment, with modified asphalt and a polyurethane adhesive.

Environmental Consideration

Custom® Building Products is committed to environmental responsibility in both products produced and in manufacturing practices. Use of this product may contribute to LEED® certification.

Suitable Substrates

  • Concrete, cement mortar, masonry
  • Cement Backerboard
  • Exterior Plywood and OSB (interior, dry areas only)
  • Exterior Decks – Contact Technical Services
  • Post-Tension Concrete – Contact Technical Services
  • Lightweight Concrete (min. 2000 psi compressive strength)
  • Gypsum-Based cement topping (min. 2000 psi compressive strength)
  • Existing ceramic tile and resilient flooring

General Surface Prep

Exterior and wet areas must have proper sloping to drains. All surfaces must be structurally sound, clean, dry and free from contaminants that would prevent a good bond. Newly prepared concrete must be troweled smooth and textured to a fine broom finish and cured for 28 days. Existing surfaces must be scarified and leveled, and all defects must be repaired. Cracks exceeding 1/8" (3 mm) should be treated in accordance with TCNA F125 or TCNA F125A.

Movement Joint Placement

Expansion joints and cold joints, as described in ANSI A108.01, should never be bridged with setting material. They must be brought through the tile work and filled with an appropriate elastomeric sealant, such as Custom's 100% Silicone. Contact Custom's Technical Services for the proper treatment of control or saw cut joints. Refer to TCNA EJ171, F125 & F125A.

Health Precautions

Wear impervious gloves and eye protection while using this product. Avoid contact with eyes or prolonged contact with skin. Wash thoroughly after handling. If eye contact occurs, rinse cautiously with water for several minutes, remove contact lenses if easy to do: continue rinsing. Immediately seek medical advice if symptoms are significant or persist. Do not take internally. KEEP OUT OF REACH OF CHILDREN.

Limitations to the Product

  • Do not bond directly to hardwood, Luan plywood, particle board, parquet, cushion or sponge-back vinyl flooring, metal, fiberglass, plastic or OSB panels.
  • Do not use as a wear surface.
  • When setting glass tile larger than 6" × 6" (15 × 15 cm), contact Custom's Technical Services for recommendations.
  • When setting dimensional stone larger than 12" × 12" (30 × 30 cm), contact Custom's Technical Services for recommendations regarding subfloor deflection requirements.

Bonding to Lightweight Cement and Gypsum Surfaces

Gypsum substrates must exceed 2000 psi (13.8 MPa) and must be fully sealed using Peel & Stick Primer.

Bonding to Plywood Surfaces

Plywood floors, including those under resilient flooring, must be structurally sound and must meet all ANSI and deflection requirements. For questions about proper subfloor installation, call Custom® Building Products.

Bonding to Existing Surfacing Material

Resilient flooring or plastic laminates must be well-bonded, as well as clean and free of all contaminates. Roughen the surface by sanding or scarifying; rinse and allow to dry. Do not sand flooring that contains asbestos. For existing well-bonded ceramic tile, mechanically abrade the surface. Rinse and allow to dry. An approved respirator should be used when sanding.

Bonding to Cutback Adhesive

Thick accumulations and powdery, brittle or weak cut back adhesive layers must be removed. Use extreme caution, as adhesives may contain asbestos fibers. Do not sand or grind the adhesive residue, as harmful dust may result. Never use adhesive removers or solvents, as they weaken or soften the adhesive and may cause it to penetrate into the concrete. The remaining residue should be no thicker than a coat of paint and should be almost transparent. Always install an adequate number of properly located test areas.

Application of Product

Application of Primer

For proper adhesion and optimal bond, prime the substrate with Peel & Stick Primer. Using a paint brush, short-nap roller or soft-push broom, apply an even coat and allow it to dry until tacky to the touch, about 30-40 minutes. When the primer does not transfer to your finger, the surface is ready for application of CrackBuster® Pro.

Full Floor Application

With the release sheet still attached, unroll and position the membrane over the area to be treated and cut the membrane to the appropriate length. Roll up half of the cut membrane, leaving the other half in position. Cut the release sheet from the rolled-up portion of the membrane and pull the membrane into position, exposing and unrolling the self-stick portion. Return to the unrolled portion of the membrane and follow the same procedure. Check the positioning; smooth wrinkles and bubbles with a flat trowel and roll with a 50 lb (23 kg) roller or apply 50 lb (23 kg) of pressure with a hand roller to ensure complete contact with the substrate. Air pockets and wrinkles should be slit then smoothed with a roller or the flat side of a trowel. Align subsequent sheets and butt-join the seams tightly but do not overlap them. Clean tools with soap and warm water.

Crack Isolation Application

With the release sheet still attached, premeasure and cut the membrane to the desired length. The membrane should extend 6"-8" (15-20 cm) beyond the length of the crack in both directions and should extend beyond both sides of the crack and at least 3 times the dimension of the tile used. Reroll the membrane and center it over the crack. Remove about 2" (5 cm) of release paper and apply it firmly to the substrate. Remove the rest of the release paper, exposing and unrolling the self-stick portion of the membrane. Secure the membrane to the substrate with a 50 lb (23 kg) roller or equivalent heavy pressure from a hand roller or flat trowel. Remove fresh adhesive from tile surfaces with a damp cloth. Clean tools in warm soapy water.

Tile and Stone Installation

Install tile or stone with a Custom® Building Products polymer-modified mortar that meets ANSI A118.4, A118.15 or A118.11 standards.

Cleaning of equipment

Clean tools and hands with water before material dries.


Store and transport in a cool dry area.

Product Maintenance

Properly installed product requires no special maintenance. Do not use as a wear surface.

Ordering Information


36" x 75' (.91 x 23 M) Rolls


40 mils

Warranty Information

Product Warranty

Obtain the applicable LIMITED PRODUCT WARRANTY at or send a written request to Custom Building Products, Inc., Five Concourse Parkway, Atlanta, GA 30328, USA. Manufactured under the authority of Custom Building Products, Inc. © 2017 Quikrete International, Inc.

Warranty Duration

When Crack Buster® Pro Crack Prevention Mat Underlayment is used as a part of a qualifying full installation system of CUSTOM products, the installation can qualify for up to a lifetime system warranty. CUSTOM will repair and/or replace, at its discretion, the affected area of the system. For more information, find details and limitations to this warranty at

Coverage Chart

Size Coverage
36" x 75' (.91 x 23 M) 225 ft² (20.9 M²)

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