How to Use Thin-Set Mortar on RedGard Waterproofing

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Things You'll Need

  • Water spray bottle

  • ¾-inch nap roller cover

  • Roller frame

  • Extension pole

  • 6-inch fiberglass mesh tape

  • Fortified thin-set mortar

  • 5-gallon bucket

  • Electric drill

  • Thin-set mixer

  • Margin trowel

  • Thin-set trowel

  • Grout

  • Grout float

  • Grout sealer


RedGard can also be used as a crack prevention membrane.

RedGard waterproofing membrane is an easy-to-install solution to prevent water leaks through horizontal and vertical installations. Using RedGard under floor and wall tile will create a barrier that will be undisturbed after the tile is installed and grouted. Water damage prevention is active from both sides of the RedGard membrane. When RedGard is wet, it is a hot, fluorescent pink color. When it dries, it is a solid, dark red, so you know when it is time to apply thin-set mortar and tiles.


RedGard Installation Method

Step 1

Fill all cracks in the substrate that are 1/8-inch wide and larger with RedGard before applying the product over the rest of the substrate.

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Step 2

Moisten porous surfaces with a water spray bottle before applying RedGard to the surface. Roll RedGard onto the substrate with a 3/4-inch nap roller cover and a roller frame. Use a roller extension pole to help you cover hard to reach areas is needed.

Step 3

Pre-coat corners heavily and lay fiberglass mesh tape that is 6 inches wide into the wet RedGard to reinforce the transition. Do the same for gaps and cracks that are 1/8 inch and wider.


Step 4

Allow the RedGard membrane to cure for 1 to 1 1/2 hours. The color will turn from pink to a solid red sheet with no pink spots when it is fully dry. It is most important that you wait for the color of the product to turn completely red as ambient conditions will make the dry time vary.

Step 5

Clean tools and hands with water before the RedGard dries.

Thin-Set Mortar Installation

Step 1

Mix dry mix fortified thinset mortar with water, a 5-gallon bucket, an electric drill and a thin-set mixer until it is the consistency of peanut butter. Allow the thin-set to set up for 5 to 10 minutes. Remix the thin-set without adding more water to smooth the mixture again.


Step 2

Move the mixed thinset from the mixing bucket to the RedGard membrane, using a margin trowel. Apply enough thin-set to cover an area that is about 3 feet by 3 feet square. Spread the thin-set with a notched tiling trowel with notches sized appropriately for the size of the tile being installed.

Step 3

Set the tile into the thin-set while it is still wet. Once the tile is set, do not touch, move, or walk on the tile for 24 hours to allow the thin-set to cure undisturbed.

Step 4

Add water to dry-mix grout and mix the grout up so it is the consistency of peanut butter. Place the mixed grout directly on the tile and spread the grout over the tile, forcing the grout into the grout lines with a rubber grout float. Allow the grout to dry for 15 minutes.


Step 5

Wipe the grout haze off of the tiles with a damp sponge. Smooth the grout lines with a corner of the grout sponge. Allow the grout to cure for 72 hours before applying grout sealer.



Kelly Nuttall

Kelly Nuttall is a student at Utah Valley University in Orem, Utah. She is set to graduate in the spring of 2011 with her bachelor's degree in technical communications. She has been writing for various websites since March of 2009.