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Using wall tile on a floor in a wet area

Question:

I am building a new home and learning things I never knew. One is regarding what tile can be put on a shower floor. I want a shower as in the attached inspiration photo. Apparently, they used a tile that is now discontinued. The new version I like is approved for a shower floor.  However, it is expensive and has divots/irregularities. I was hoping for something smoother and in budget.

Most black subway tile is not annotated as for shower floors. However, my sales representative is telling me that it is perfectly fine to use a wall tile on a shower floor. She is recommending a specific glazed ceramic wall tile 3×12 (black glossy).  Is she correct?

Answer – Part 1

Any tile considered for use in any application should have the manufacturer’s approval for the intended use. I suggest asking your distributor/salesperson to obtain the technical datasheet for the tile you are interested in. The TDS should specifically include information if the tile is acceptable for use on a floor in a wet area (such as a shower floor). If the TDS does not include this information, you can call the manufacturer directly to request this information or select a tile that is specifically rated for use on a shower floor.

Additionally, the durability of the tile in this application may or may not be affected by the type of shower pan being specified for this installation and its ability to properly support a soft-bodied wall tile.

Another consideration is the pattern and drainage system. If a running bond pattern is used (with a conical pitched floor to a center drain) it would result in lippage and accompanying puddling.  A running bond pattern with a linear drain system could help minimize any puddling. 

As you have discovered, tile is a complex science and art.  One of the most critical installations to construct is a shower. To ensure that you get all of the correct technical information you need for your installation, I strongly encourage you to employ an NTCA member contractor and a CTEF Certified Tile Installer. These contractors and installers own, understand, and apply the tile industry’s recognized standards, methods, best practices, and follow manufacturer instructions in the installations they construct. NTCA Members and CTEF CTI certified installers have direct unlimited access to the NTCA/CTEF technical team for training and detailed industry standards-based support in every installation they construct.

Please review the Ceramic Tile Education Foundation’s homeowner’s guide to hiring a qualified installer:  https://www.ceramictilefoundation.org/homeowners-guide-to-hiring-qualified-tile-installer

To find an NTCA member contractor in your area: https://www.tile-assn.com/search/custom.asp?id=2759

To find a CTI installer in your area:  https://www.ceramictilefoundation.org/find-certified-tile-installers

Question – Part 2 – 50% offset/lippage and saving money to cut large tiles into small tiles

Thank you so much for your help in my questions regarding shower tiles.  If you don’t mind, one other issue has arisen and I’d like to know the correct answer. It appears to my untrained eye that most 12″x24″ tile is laid so that each abuts the 2 adjacent tiles by 50% each. However, the sales associate said some governing body (Tile Layer’s Association??) had rules against that because of “lippage”?  Are there rules on how tile should be laid? If so, where is the resource for that? I’d like to know as being the homeowner, I assume I’m ultimately responsible for catching mistakes in the construction of my new home.

Also, is it better to purchase (at high cost) precut 4″x12″ or is it acceptable to have those cut by installers from 12″x24″?  A sales associate said the former is the better option.

Answer – Part 2 – 50% offset/lippage and saving money to cut large tiles into small tiles

These are excellent questions that are answered by the tile industry’s written standards and best practices.

It sounds like you are selecting a tile for a builder’s installer or tile contractor to the installer. I suggest asking your builder if their installer or contractor owns and applies the methods and standards in the Tile Council of North America Handbook for Ceramic, Glass and Stone Installation (TCNA Handbook), and the American National Standard Specifications for the Installation of Ceramic Tile.  These are the documents that answer your questions.

The associate you are working with is giving you solid advice based on these standards. The retailer you are working with is a strong supporter of NTCA and their staff and associates, many of which have attended our training programs, are knowledgeable about these things.

To answer your first question about the 50% offset for the 12×24 tile:

ANSI A108.02 Section 4.3.8.2 is where the answer is.  I will paraphrase what it says; When tiles with sides longer than 15” are being set with their long sides next to each other they shall be set in a pattern with an offset of 33% or less. If an offset more than 33% is desired (such as a 50% offset), the specifier and owner must approve a mock-up and agree to the lippage that may result from this type of pattern being installed.

The reason for this is that some tiles have what is called warpage as part of their manufacturing process. Warpage is when the tile is bowed in the middle. The ends of these tiles may be lower than in the middle of the tile.  When tiles longer than 15” are set next to each other in a 50% offset, this puts the high part of the middle of one tile directly opposite of the low part of the end of the adjacent tile. This can result in a difference in the height elevation of the plane between the two tiles.  This difference in the plane is known as lippage.  To quote the TCNA Handbook: “Lippage is a condition where one edge of a tile is higher than an adjacent tile, giving the finished surface an uneven appearance. Lippage is inherent in all ceramic installation methods and may also be unavoidable due to the tile tolerances, in accordance with ANSI A137.1”.

Not all tiles have warpage.  There are industry standards that describe acceptable warpage. Some tiles are made to meet those standards, some are not. The tile manufacturer can tell you if their tile meets the standard for warpage.  It is in ANSI A137.1.

Some manufacturers will have specific offset requirements for their tiles.  They may require a 20% or 25% maximum offset.

So, if you would like a 50% offset, you need to ask your tile contractor to lay them out or physically install a few so you can view them as they will look in the finished installation. At that time you would approve and accept (in writing) any lippage that occurs as a result of setting them at a 50% offset.  You will own and live with this installation – it is your decision to approve or reject the mockup.

To answer your second question about cutting 4×12 tiles out of 12×24 tiles:

The TCNA Handbook for Ceramic, Glass and Stone Tile Installation states:  Tiles should not be field-cut to size to accomplish modular patterns or to align grout joints, as field-cut edges will be dissimilar from factory edges and cannot be held to the same squareness tolerance.

This is not the desired practice.  In reality, it is not less expensive as your tile contractor should rightly be expected to charge labor and materials to cut down and smooth or hone the tiles. The tile contractor likely has excellent tools, but they may not be of the same grade as the tile factory and with human error, there may be variations from tile to tile after they are cut.  Expect the labor price will increase as more time is needed to ensure all tiles are well matched and finished.

Depending on the tile body and glaze, this practice may present an opportunity for chipped tiles. A large amount of additional tile may need to be purchased at the outset to account for this possibility.

For review:

As I mentioned in our last conversation, to ensure that you get all of the correct technical information you need for your installation, I strongly encourage you to employ an NTCA member contractor and a CTEF Certified Tile Installer. These contractors and installers own, understand, and apply the tile industry’s recognized standards, methods, best practices, and follow manufacturer instructions in the installations they construct.  NTCA Members and CTEF CTI certified installers have direct unlimited access to the NTCA/CTEF technical team for training and detailed industry standards-based support in every installation they construct.

Please refer to the links above.

I hope this information helps.

Mark Heinlein

Mark Heinlein is Training Director for the National Tile Contractors Association. He is Certified Tile Installer #1112 and currently a Ceramic Tile Education Foundation evaluator for the Certified Tile Installer program. Heinlein was the owner of Mark Heinlein Surfaces of Negaunee, Michigan.