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HomeTechnicalAsk the ExpertsIs marble ideal to use for a shower floor?

Is marble ideal to use for a shower floor?


I am trying to find where TCNA speaks specifically to “not” using marble on shower floors. Can you tell me where to find that in the 2021 manual? I am looking for something “official” to show a customer who is insistent on having an elaborate Carrara or Calacatta marble mosaic on her shower floor, and other stores in town are not cautioning her against this.

Also, in the process of doing a Google search to try to find this information (no luck), I did come across a TileLetter article from 2020 that basically argues against the idea that marble material is not the ideal product for a shower floor; that it goes back to installation products and process used. I’d appreciate any input you might share with me! 


There are several industry-recognized installations that incorporate stone in a shower assembly found in the TCNA Handbook. The materials section of each Handbook method directs you to the natural stone selection guide found at the beginning of the Handbook

There is not a method for stone tile use in steam showers found in the TCNA Handbook. In the Natural Stone Institute Design Manual there is a section called “Wet Areas” that says not to use moisture-sensitive stone or flawed stone in wet areas. 

Stone tiles have a classification system of A, B, C, and D. These classifications are based on the amount of flaws and fillers that are found in the stone. The Design Manual cautions against the use of classification C and D stones in some wet areas. In addition, page 264 of the current NTCA Reference Manual addresses this situation in “Stone in Wet Areas.” 

The TileLetter article you are referencing is in the Tile & Stone section of the July 2020 issue, found here: https://www.tileletter.com/marble-moisture-discoloration/. I hope this information helps. 

– NTCA Technical Team 

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