Waterproofing Shower Walls before Tiling

Make Sure to Waterproof Shower Walls Prior to Installing Tiles

By Mark J. Donovan

It is important to waterproof your shower walls prior to tiling them to prevent moisture and mold problems behind them. To waterproof shower walls I prefer to use 15lb roofing felt paper or plastic on the framed shower walls prior to installing a cement backerboard. The felt paper or plastic acts as the moisture barrier and the cement backerboard will not swell or decay if water comes in contact with it.

If not using cement backerboard on the shower walls, or if you neglected to apply felt paper or plastic on the framed shower walls prior to installing the cement backerboard, there are liquid waterproofing products that you can use.

Redgard, for example, is a liquid waterproofing membrane product that you can apply to the shower wall surfaces to form the moisture seal.

If using a cement backerboard and you did not install felt or plastic behind it first, apply Redgard over the cement backerboard after the seams have been taped and mudded with a thinset mortar. Also, it is important to use an alkaline resistant tape when taping the cement backerboard.

Redgard can be applied with a brush or roller. Typically you want to apply 2 to 3 coats of it and allow it time to fully dry prior to installing the shower tiles. Thinset mortar can be applied directly over the Redgard for attaching the ceramic tiles.

Redgard can also be used on shower walls not constructed out of cement backerboard. For example it works well over Hardibacker and Kerdi shower systems. As a matter of fact you must use a waterproofing product over these surfaces to ensure that they do not get wet. If they do they can eventually breakdown, unlike cement backerboard.

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Greenboard, plywood, or drywall should never be used as a shower wall surface, even with Redgard. Any moisture penetration whatsoever could lead to mold and mildew problems.

Also, never apply Redgard over cement backerboard walls, if there is a moisture barrier already behind it. This could lead to moisture being trapped between the two effective moisture barriers and causing mold growth.

For information on installing a shower pan membrane liner for a ceramic tile shower, see the Shower Pan Membrane Liner Installation Ebook from HomeAdditionPlus.com.  The Shower Pan Membrane Liner EBook will quickly teach you the step-by-step process for installing the shower pan membrane liner correctly. It includes instructions on framing the shower stall, pouring the pre-slope and shower base mortar, and installing the shower pan membrane liner.

See HomeAdditionPlus.com’s Ceramic Tile Calculator

See my “How to Tile a Custom Ceramic Tile Shower” Ebook to learn how to tile your own shower:  For a detailed set of instructions on tiling a shower floor and walls, including pictures for every step in the process, see my “How to Tile Custom Ceramic Tile Shower Ebook”.

Related Information

Additional Ceramic Tile Resources from Amazon.com


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