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ask the experts

Shower Areas

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Ask the Experts Q&As are culled from member inquiries to NTCA’s Technical Support staff. To become a member and make use of personal, targeted answers from Technical Support staff to your installation questions, contact Jim Olson.
QUESTION I have seen installers use thinset against the studs when installing concrete board in order to shim out the studs that are recessed, and install the boards with no dips or humps in the shower walls. Is this a proper method and an okay way to fix walls with questionable framing? Or would it be better to install the board to the wood studs and fill the low areas with thinset after the board is installed?

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ANSWER Some manufacturers may allow that certain of their A118.1/.4/.11/.15 thinset mortars may be used for minor rendering of walls in a wet area so long as the maximum bond coat thickness is not exceeded and that proper cure times are allowed for, and minimum required coverage is achieved.
In regards to “wet shimming” behind backer board to framing or substructure: If a board manufacturer recommends doing this with their board, ask what mortar they recommend using. Then ask whether the mortar manufacturer stands behind that application or use of their product that may not have been designed for that particular application. If this is not recommended by the board and thinset manufacturer, the risk for long-term system performance is on you.
Shims installed behind the board, and cementitious patch material (designed for this purpose) installed over the board are two alternative methods for ensuring substrate flatness for you to consider.
– NTCA Technical Team

QUESTION We are building a new home and my designer is insisting on a walk-in shower. We had a disaster with the last walk-in shower we had done. It doesn’t seem like tile lasts long in a shower. How long can a properly-installed shower last?
ANSWER When installed using proper materials, methods, industry standards and techniques, tile installations in wet areas such as floors, walls, showers, pools, etc., can last a very long time.
There are many criteria that support or affect a tile installation that is in a wet area or is submerged or partially submerged. These include: type of tile, type of substrate, type of mortar, type of grout, whether there is a waterproofing membrane, method of installation, expansion joint placement, how well the tile was installed, etc.
If an installation was not designed to wet area standards or installed with materials not designed for use in a wet area, or if it was not installed according to approved wet area methods and standards, there is a good chance of some type of failure within the system after being exposed to standing water for an extended period of time.
If you are not a tile contractor, you will want to locate, interview and hire an NTCA member contractor, NTCA Five-Star Contractor, and a CTEF Certified Tile Installer that can help you with your tile installations.