Products : Setting : Additives : Thin-Set & Mortar Admix

Thin-Set & Mortar Admix

A liquid polymer designed to be used in place of water to increase performance of cement mortar beds, non-modified, thin-set mortars and cement-based grouts. It improves working characteristics and performance of cement-based mixes to boost water resistance, shock resistance and freeze-thaw capabilities for tile, stone or masonry installations. Increases performance of non-modified thin-set mortars for setting dense tile and setting over hard-to-bond surfaces. Thin-Set & Mortar Admix can be used with non-modified, thin-set mortars such as, CustomBlend® Thin-Set Mortar and Uncoupling Mat Mortar. It can also be used with Saltillo Grout Mix.

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Key Features

  • Increases bond strength and performance
  • Improves water resistance
  • Mix with CustomBlend


When mixed with non-modified thin-set mortars and mortar bed mixes:

  • Improves bond strength
  • Improves freeze-thaw durability
  • Improves Flexibility

Increases performance for:

  • Installation of hard-to-bond tiles
  • Interior and exterior applications


Applicable Standards

American National Standards Institute (ANSI) ANSI A108.5; A118.4; A118.11 of the American National Standards for the Installation of Ceramic Tile

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

Composition of Product

Liquid Latex

Environmental Consideration

Custom® Building Products is committed to environmental responsibility in both products produced and in manufacturing practices. Use of this product can contribute towards LEED® v3 certification:

  • Up to 2 points towards MR Credit 5, Regional Materials
  • Up to 1 point towards IEQ Credit 4.1, Low-Emitting Materials – Adhesives & Sealants

Suitable Tile Types

  • Vitreous, semi-vitreous or non-vitreous tile: ceramic, mosaic, quarry, cement body tile
  • Impervious porcelain and glass tile
  • Brick and stone veneer
  • Cement-based precast terrazzo
  • Natural stone tile

Suitable Substrates

  • Concrete, mortar beds, masonry, Portland cement plaster
  • WonderBoard® Lite cement backerboards
  • Liquid applied waterproofing membranes such as RedGard® and Custom® 9240
  • Crack prevention sheet membranes such as Crack Buster® Pro
  • Exterior Grade Plywood (interior residential and light commercial dry areas)
  • Gypsum wallboard (interior dry areas)
  • Existing ceramic tile
  • Fully-bonded sheet vinyl flooring
  • Plastic laminates
  • Cutback adhesive (see preparation instructions)

General Surface Prep

USE CHEMICAL-RESISTANT GLOVES, such as nitrile, when handling product.

Surfaces must be structurally sound, clean, dry and free from grease, oil, dirt, curing compounds, sealers, adhesives or any other contaminant that would prevent a good bond. Glossy or painted surfaces must be sanded, stripped and cleaned of waxes, dirt or any contaminants. Concrete must be cured 28 days and accept water penetration. Concrete must be free of efflorescence and not subject to hydrostatic pressure. Concrete slabs should have a broomed or brushed finish to enhance the bond. Plywood flooring including those under resilient flooring must be structurally sound and meet all ANSI and deflection requirements. For questions about proper subfloor installation, call Technical Services. Smooth concrete surfaces, existing glazed tile, terrazzo, or polished stone should be roughened or scarified. Sheet vinyl must be-well bonded and stripped of old finish. Roughen the surface by sanding or scarifying, rinse and allow to dry. Expansion joints should never be bridged with setting material. Do not sand flooring materials containing asbestos. Ambient temperature, surfaces and materials should be maintained at a temperature above 50° F (10° C) or below 100° F (38° C) for 72 hours.

Movement Joint Placement

Expansion joints, control joints and cold joints should never be bridged with setting material. They must be brought through the tile work and filled with an appropriate elastomeric sealant.

Health Precautions

Contains latex emulsions. Wear rubber gloves and eye protection. Avoid eye and skin contact. If eye contact occurs, immediately flush with water for 15 minutes and consult a physician immediately. If skin contact occurs, wash immediately with soap and water. Dried material becomes extremely difficult to remove. KEEP OUT OF REACH OF CHILDREN.

Limitations to the Product

Bonding to Concrete Surfaces

Concrete or plaster must be fully cured and must accept water penetration. Test by sprinkling water on various areas of the substrate. If water penetrates, then a good bond can be achieved; if water beads, surface contaminants are present, and loss of adhesion may occur. Contaminants should be mechanically removed before installation. Concrete must be free of efflorescence and not subject to hydrostatic pressure. Concrete slabs should have a broomed or brushed finish to enhance the bond. Smooth concrete slabs must be mechanically abraded to ensure a good bond.

Bonding to Plywood Surfaces

Plywood floors, including those under resilient flooring, must be structurally sound and must meet all ANSI A108.01 Part 3.4 requirements. See TCNA F150. For questions about proper subfloor installation, call Custom® Building Products.

Bonding to Backerboards

WonderBoard® Lite Backerboard may be installed over plywood subfloors as an alternative to an additional layer of plywood,. Refer to TCNA F144.

Bonding to Existing Surfacing Material

Plywood flooring must be structurally sound and meet all ANSI and deflection requirements. Resilient flooring or plastic laminates must be well-bonded, clean and free of all contaminates. Roughen the surface by sanding or scarifying, rinse and allow to dry. Do not sand flooring containing asbestos. For existing well-bonded ceramic tile, mechanically abrade with carborundum stone. Rinse and allow to dry. When sanding we recommend the use of an approved respirator.

Bonding to Cutback Adhesive

Adhesive layers must be removed as they reduce mortar bond strength to cement surfaces. Use extreme caution as adhesives may contain asbestos fibers. Do not sand or grind adhesive residue, as harmful dust may result. Never use adhesive removers or solvents, as they soften the adhesive and may cause it to penetrate into the concrete. Adhesive residue must be wet-scraped to the finished surface of the concrete, leaving only the transparent staining from the glue. Do a test bond area first, to determine desirable results. Refer to the RFCI Pamphlet, "Recommended Work Practices for Removal of Resilient Floor Coverings", for further information.

Mixing Procedures


Refer to individual product instructions. Mixing details for Thin-Set & Mortar Admix will vary dependant upon non-modified mortar used. See the mixing instructions on CustomBlend® or Uncoupling Mat Mortar bag or data sheet for specific directions.


Thin-Set & Mortar Admix may be used as a fortifying additive to site-mixed or bagged Portland cement and sand mixtures common to masonry or floated mortar beds. Mix 1 part Thin-Set & Mortar Admix with 1 part clean water and use as a direct replacement for the water requirement in any mortar mix. Thin-Set & Mortar Admix can be used full strength for improved performance.

The total amount of liquid added will vary.


When installing tile over wood substrates and when increased tensile and flexural grout qualities are necessary, use Thin-Set & Mortar Admix with water. Mix 1 part clean water with 1 part Thin-Set & Mortar Admix prior to mixing liquid with Portland cement grout. Remove excess grout from surface of tile as soon as possible after grouting, as latex-fortified grout becomes extremely difficult to remove when dry. Not for use with Custom's® Polyblend® Grout or Prism® SureColor® Grout.

Cleaning of equipment

Clean with water before material dries.

Mortar: Clean with water while mortar is fresh.

Grout: Refer to instructions of non-modified grout for installation and cleaning instructions.


Keep from freezing. Close container after each use.

Product Maintenance

Properly installed product requires no special maintenance.

Expected Wear

Properly installed tile will last for more than 60 years.

Ordering Information


  • 2.5 gal (9.46 L) bottle
  • Canada 2.5 gal (9.46 L) bottle

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.

Coverage Chart

Refer to CustomBlend® Standard Thin-Set Mortar or Uncoupling Mat Mortar. Coverage for mortar beds will vary dependent upon quantity mixed.

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