TECH TIP TUESDAY: Q & A WITH NTCA TRAINING DIRECTOR MARK HEINLEIN

Consumer Question:

The concern that I have at this time is the installation of soft joints at the change of plane in the corners of the tub surround. The product is a 12″ x 24″ marble.

 

 

 

 

 

 

 

 

 

 

 

The tile pieces most definitely butt up against one another and it is my belief that the tile installer is going to place a bead of caulk up along the exposed surface of the two.
I am concerned this is not a soft joint to allow for movement of the tiles, but rather a bead of caulk to hide the connection (more aesthetic than functional).  Would this be a concern for you? If so, what types of issues may I have in the future if there is no soft joint?

 

Mark’s Reply:

Thank you for contacting the National Tile Contractors Association!

The Tile Council of North America Handbook and ANSI Standards require functioning open movement joints at changes in plane.  If those joints are tight butted there will be no room for them to properly function to absorb the natural flexing, movement, expansion and contraction that is inherent in all construction.  Without being there in person I am not able to comment definitively however, the joints in your photos do appear to be either tight-butted or have too tight of a joint.

Movement joints at changes in plane are required and are functional and should be filled with a flexible sealant appropriate for the area it is being used.  For a wet environment such as a shower, an ASTM C920 sealant such as a 100% silicone or urethane can be used. These sealants are manufactured to match as closely as possible the grout color.

Before applying the sealant in your marble installation, a test sample should be done along the edge of a scrap piece of marble.  Some colors of sealants have colorants that may absorb into the soft stone and may cause staining that can be visible along the edge of the tile. This is a common pre-installation test that should be done with all marble installations.  A phone call to the technical department of the sealant manufacturer may help determine which of their colors are best suited for soft stone.

The best way to find an NTCA Recognized Consultant in your area is to review our list at this link:  http://www.tile-assn.com/?page=recconsultants. These are highly regarded consultants that may travel regionally or nationally.  Feel free to let them know about the conversations we have been having.

I hope this helps.


Mark Heinlein, NTCA Training Director

TECH TIP TUESDAY: Q & A WITH NTCA TRAINING DIRECTOR MARK HEINLEIN

Contractor Question:

Mark,
I am thinking about putting a heating TapeMat in the floor of my bathroom.  The manufacturer’s literature suggests a modified thin-set mortar.  I am using a large format tile (12” x 24”).  I am placing the tile on a 3/4 inch plywood subfloor with a 1/4 inch Hardy board backer.  The floor is supported by 2”x12” floor joists spaced at 16” on center.  The bathroom is L shaped and is  8’x4’ with a 3’ L.  The 8’ wall is an exterior wall. Would an unmodified mortar work as well? Is it even advisable to use a modified mortar with a large format tile?

Mark’s Reply:

Thanks for the info.

Assuming ceramic/porcelain tile is being installed, the industry recognized method found in TCNA Handbook is RH135-16.  The method describes the details for an electric radiant heat system encapsulated in mortar over backer board on a plywood subfloor with joists 16” on center, which is the installation you have described.

It sounds like you are not installing a waterproofing membrane in the system.  In that case, the required thinset mortar for the cementitious bond coat is an ANSI A118.15.  In other words, an Improved Modified Dry-Set Cement Mortar is required.

The mortar you select should have the words “Meets ANSI A118.15” stamped on the package.  Be certain to carefully follow the mortar manufacturer’s instructions for the proper amount of water, mixing instructions, slaking time, open time, etc.

You asked whether it is advisable to use a modified mortar with a large format tile.  It is.  In fact, many manufacturers are now producing highly modified mortars specifically designed for Large and Heavy Tile.  You may find mortars labeled as “LHT” for this reason.  These mortars have specific properties to support the installation of large and heavy tiles on floors and walls.  Some allow for a thicker bond coat.  This is the type of mortar I would look for when installing an electrical heating tape mat system in the bond coat layer.

If you are using a membrane in the system, it may be advisable to use a less highly modified mortar (such as an A118.4) or even an unmodified thinset mortar (A118.1).  Check with the manufacturer of the membrane for their specific mortar recommendation.

Please make certain the surface of your plywood subfloor is flat to meet the industry standard tolerance of 1/8” in 10’ as required by ANSI A108 before you install the backer board.  This will ensure you have a flat finished tile surface on your large format tile installation.  Use a rapid setting patch material to fill low spots and a belt sander on the high spots of the plywood.  Do not use more or less thinset to help you flatten your installation while you set tile.  Doing so will prove problematic for you and your installation.

Membership in the National Tile Contractors Association is a valuable resource for any professional tile contractor or any contractor who installs tile.  NTCA is committed to improving installations and performance of contractors throughout the tile industry.  Our primary mission is training based on the tile industry standards I have described above.  Every installer should own and be familiar with the standards, methods and details that guide the tile industry.  I would be happy to discuss with you and your tile installation contractors the many benefits of membership in NTCA.  Please feel free to contact me, or Jim Olson at [email protected] for more information.  Also please visit our website at www.tile-assn.com.

The Ceramic Tile Education Foundation (CTEF) supports education and training in the tile industry.  The Certified Tile Installer (CTI) program is a highly sought after certification for tile installers who wish to achieve a higher level of professionalism and recognition in the tile industry.  Please visit the CTEF website at https://www.ceramictilefoundation.org to locate a Certified Tile Installer or contact Kevin Insalato at [email protected] for more information on how a contractor can become a CTI.

I hope this helps.

Mark Heinlein, NTCA Training Director

 

Tech Tip Tuesday: Q & A With NTCA Training Director Mark Heinlein

Consumer Question:

Hi! Recently, our new tile floor began cracking. Our builder took up the damaged areas, fixed deflection, and replaced damaged tiles. Now, more tiles in other areas are cracking. Is it standard practice to continue piecing the floor together or is it better to rip out the whole floor?

Answer:

Thank you for contacting the National Tile Contractors Association.

It is not at all standard to have to make repairs like this to a new tile installation.

What is standard is to ensure the structure including the subfloor and substrates that will support the tile installation are properly engineered, designed and constructed before the tile installation begins. There are standard requirements to meet tolerances for deflection.  When deflection and substructure requirements are met, tile installations can be designed and installed using additional tile industry standards, methods, best practices and techniques.

The primary tile industry standards are found in these publications:
American National Standards Institute Specifications for the Installation of Ceramic Tile (ANSI A108)
American National Standards Institute Material Specifications (ANSI A118)
Tile Council of North America (TCNA) Handbook
In addition to deflection, there may be other factors that could be leading to this failure in your tile system.  Tile installations are complex.  Every aspect of the installation must be performed according to industry standards and material manufacturer instructions to ensure a long lasting successful installation.

Ask your tile installer which standards and methods from the above listed publications they followed to install your project.

Is your tile contractor a Ceramic Tile Education Foundation Certified Tile Installer (CTI)?  CTIs are recognized by the tile industry to have the necessary knowledge of these industry standards along with the proven skills and experience to construct long lasting tile installations.  You can search the list of CTIs in your area at this link:  https://www.ceramictilefoundation.org/find-certified-tile-installers

Is your installer an NTCA member or an NTCA 5 Star Contractor?  NTCA member contractors can be located here:http://www.tile-assn.com/search/custom.asp?id=2759  Membership in the NTCA is a valuable resource for any professional tile contractor or any contractor who installs tile.  NTCA is committed to improving installations and performance of contractors throughout the tile industry.  Our primary mission is training based on the tile industry standards I described above.

NTCA 5 Star Contractors that employe CTIs can be located at this link:  http://www.tile-assn.com/search/custom.asp?id=2838

Every installer should own and be familiar with the standards, methods and details that guide the tile industry.  If your contractor is not familiar with the standards or if they are not an NTCA member or Certified Tile Installer, I would be happy to discuss with them the importance of these programs.  Please feel free to have them contact me, or Jim Olson at [email protected] for more information.

The NTCA and the entire American tile industry want you to have a beautiful and functional and safe installation that will stand the test of time and that will make you happy and comfortable and proud to own. Employing Certified Tile Installers and NTCA member contractors is a step in the right direction to ensure a successful tile installation based on tile industry standards.

I hope this helps.

Mark

CTEF Regional Evaluators Expand Certified Tile Installer (CTI) Hands-on Testing Program

The Ceramic Tile Education Foundation (CTEF) has developed a Regional Evaluators (RE) program to expand the Certified Tile Installer (CTI) Program hands-on testing. The program is led by Regional Evaluator Coordinator Kevin Insalato who reports to Scott Carothers, Director of Training and Education for CTEF.

“It is critical for the future of the tile industry that homeowners, architects, designers and commercial business owners have the option of qualified labor for their tile installation projects so the installations not only look beautiful, but also perform consistently over time,” says Carothers. “The CTI program was developed to provide that level of assurance to those seeking professional tile installers. With the Regional Evaluator program, CTEF can significantly grow the number of CTIs and the level of tile installation competence available across the United States.”

What is the Regional Evaluator Program?

Regional Evaluators are themselves Certified Tile Installers who take additional training to evaluate the hands-on portion of the Certified Tile Installer Program test. They must know how to set up the testing modules, conduct the hands-on test, score the 100-point evaluation, and assist installers in furthering their understanding of the proper installation of ceramic tile.

They are regionally based and able to organize and conduct hands-on testing within their region which greatly expands the reach of the CTI program. This also means that installers no longer need wait until classes reach 10 or more students before they are able to take the hands-on portion of the exam and achieve industry-recognized certification and validation of their skills and knowledge.

Kevin Insalato of California Flooring in the Chicago area, serves as Regional Evaluator Coordinator for the program and has kicked it off with the following sixteen Regional Evaluators:

Joe Kerber, CTI # 217, Kerber Tile Marble & Stone – Shakopee, MN
Robb Roderick, CTI # 727, NTCA Trainer – West Coast USA
Mike Corona, CTI # 923, Corona Marble & Tile, Woodbine, MD
Shon Parker, CTI #999, Hawthorne Tile, Portland, OR
Dave Rogers CTI # 1029, Welch Tile – Kent City, MI
Rafael Lopez, CTI # 1100, California Flooring – Manteno, IL
Mark Heinlein, CTI # 1112, NTCA Trainer – East Coast USA
Tom Cravillion, CTI # 1116, Cravillion Tile & Stone – Plymouth, WI
Matt Newbold, CTI # 1118, Elite Tile Setters – Lehi, UT
Triniti Vigil, CTI # 1144, J&R Tile – San Antonio, TX
Brad Denny, CTI # 1190, Nichols Tile & Terrazzo – Joelton, TN
Dan Hecox, CTI # 1215, Hecox Construction – York, NE
Jason McDaniel, CTI #1273, Stoneman Construction, Stafford, OR
Todd Kozey, CTI # 1285, Complete Contracting Services – Fraser, MI
Ed Siebern, CTI # 1289, Mourelatos Tile Pro, Tucson, AZ
John Mourelatos, CTI # 1290, Mourelatos Tile Pro, Tucson, AZ
“With the Regional Evaluator Program, we can now take the CTI hands-on test to installers, retailers, and tile contractors around the country increasing the number of qualified installers available to the marketplace,” says Insalato. “That’s exciting!”

The program will initially utilize sixteen REs and eventually include a minimum of 50 Regional Evaluators. For more information about the Regional Evaluator program, visit https://www.ceramictilefoundation.org/regional-evaluators

What is the Certified Tile Installer Program?

The CTI designation identifies the professional installer who has reached a level of proficiency to independently and consistently produce a sound tile installation that displays good workmanship. Certification is the validation of the skills and knowledge of the men and women who presently are installing tile successfully in the United States.

To qualify for the CTI Program, installers must have at least two years of experience as the lead installer setting ceramic tile on a full-time basis. This means having full responsibility for substrate prep, layout, coordinating with other trades along with properly installing underlayment, tile, grout and sealant materials.

The CTI test is a two-part examination consisting of:

A written test which is an open-book, 155 question, multiple-choice exam that can be taken online at home or the office as the installer’s schedule allows.
A hands-on test which is monitored and assessed by Regional Evaluators all across the United States. In it, installers must demonstrate their ability to execute a complex layout and proper installation of vapor retarder membrane, backer board, tile (walls and floors), cementitious grout, and flexible sealant (caulk). For each installation material, the applicant is scored on the various aspects of workmanship relevant to producing an installation that will endure use and satisfy the discriminating client.
The CTI Program: Recognized by the Tile Industry

The Ceramic Tile Education Foundation (CTEF) which sponsors the CTI program is supported by all segments of the ceramic tile industry. CTEF is headquartered in Pendleton, South Carolina, near Clemson University and in close proximity to the offices of the Tile Council of North America (TCNA).

The Ceramic Tile Education Foundation (CTEF) provides education and installer certification for professionals working in the ceramic tile and stone industry. The CTEF Certified Tile Installer (CTI) program is the only third-party assessment of installer skill and knowledge which is recognized by the tile industry.

To register for the CTI tests, please visit https://www.ceramictilefoundation.org/events, select the test date and location of your choice, and make your payment through the secure third-party site. The study materials will be shipped out to your home or office the same day.

Tech Tip Tuesday: Q & A With NTCA Technical Trainer Robb Roderick

QUESTION:

I have someone in Florida who is arguing that he has never heard of needing a crack suppression membrane for glass, particularly in pools. Can you suggest some verbiage here?

ANSWER: 

Thank you for contacting NTCA. On page 8 of the glass tile selection and installation guide in the TCNA handbook. It states, “glass tile is generally more vulnerable to crack propagation than ceramic tile. Where opacity allows, the glass tile manufacturer may recommend the use of a ANSI A118.12 crack isolation membrane for large format glass.

Also, on page 21 in the membrane selection guide, glass tile is listed as material in which  crack isolation membranes can eliminate cracks caused by in plane movement of the substrate.

On page 94 it shows method F125 for installation of crack isolation membranes. The handbook also shows Method P601 and P602 for pool and water features.

 

-Robb Roderick,

NTCA Technical Trainer

Tech Tip Tuesday – August 15, 2017

Q: Right now, I have engineered hardhoods that float over a concrete slab (second floor/above grade).  There have been water leak issues every one to two years usually in summer since I moved in 7 years ago, and no one seems able to fix it.  I’ve been told the water is getting in through the door, or from flashing outside, or from the slab below as water vapor, or that the aluminum slider is leaking/sweating, and that sunlight could also be making it worse.  I’ve never actually seen any water, even when the slab was exposed for several months two summers ago with frequent heavy DC thunderstorms (just a small area of wet concrete once and the discolored and cupping wood, which scrapes against the door).

 

 

 

 

 

 

 

 

What I hope to find is a solution that will work regardless of the moisture source.  I’m not a pro but propose cutting a square for an entryway there and installing outdoor rated porcelain tile (2 that are 12 x 24 or possibly 4 creating a two foot by four foot entry — although I prefer the smaller option).  The tiles would be surrounded by schluter strips, then the existing wood beyond that.  So here are my questions:

(1) Do you think that will work?
(2) If so, should I seal the concrete (maybe with Redgard), or will that make any potential water vapor migrate further into the unit and damage the hardwoods?  I’d rather have tile issues than wood issues at this point so I don’t have to replace the entire wood in that room.
(3) Any other advice?

 

A:

Thank you for contacting me at the National Tile Contractors Association.

You should not be seeing any water coming in through or under the door sill or into the concrete like this.  The problem of water entering the structure needs to be resolved before installing any floor surface.

In my opinion your problem could be with the door itself, or the installation of the door, or the installation of the deck and it’s framing, or the installation of flashing at the exposed edge of the slab, or any combination of these things.

I have seen this problem before. The subfloor kept getting saturated every time it rained.  The finish floor could not be installed.  The problem was improper installation of a very expensive door unit by the general contractor.  The contractor figured they had installed hundreds of doors and they didn’t need to follow the manufacturer instructions.  After numerous attempts to add more sealant and after removing and replacing the door at least two times, a manufacturer rep came onsite to monitor the installation a third time and, using the printed instructions for the door, directed the contractor on it’s installation.  Problem solved.  The door never leaked again.

Here’s a simple test you can try. Spray the door and sill with a hose or sprinkle water on it with a garden watering can to mimic rain.  Does water come in?  Does it come in under/through the sill?  Does it come in through the door sweep?  If it does, there is a problem with the door / sill and/or it’s installation.  Again, no water should come in under the sill or through the sweep or other door component.  I encourage you to contact the manufacturer of the door unit and obtain their original installation instructions and attempt to determine whether the door was properly installed.  You may have to have the door removed, examined, and reinstalled using the instructions to make this determination.

As you have already been advised, the water intrusion may be originating with the flashing (or lack of flashing) and/or the deck installation and/or the installation of the sill and door.  Water may indeed be gathering in the leading edge of the slab under the deck and becoming saturated and wicking into the top corner of the slab and up under the sill and into the subfloor area.   You need to have that issue properly examined and properly resolved.   I recommend hiring a recognized, licensed, experience, trusted general contractor and have them give you a proper inspection and strategy for correction.  Be prepared to have them remove some deck boards to see what’s going on there.

You need to get the problem fixed that is allowing the water intrusion before you make a decision as to what to do for the floor finish.

There are methods to go about installing the tile, but you don’t want to have water intrusion into your structure. If left unresolved it’s persistent presence may likely  create other, as yet unforeseen problems.

After you have resolved the water intrusion and decide that you’d like to install tile, please get back in touch and I can help point you in the right direction for a proper tile installation.

I hope this helps,

Mark Heinlein, NTCA Trainer/Presenter

 

Ask the Experts – August 2017

QUESTION

An architect has requested my input relative to developing a labor and material specification for installing new porcelain floor tile over existing granite floor tiles in a high-traffic lobby in a commercial office building. Can you direct me to any relevant literature or information that addresses such applications? Thanks.

ANSWER

I suggest referring your architect to the 2016 TCNA Handbook methods TR611, TR711 and particularly TR712. Please note that if the installation is not, or cannot be made acceptable for tiling over with a thin bed system, Method F111, or another method, may be required.

As described in TR712, it is critical that the existing installation be sound, well bonded and without structural cracks. It must be determined if the existing installation will properly support the new installation. The existing tile and its bond to the substrate and the condition of the substrate will all reflect on the performance of the new installation. If there are existing structural cracks, their cause will have to be explored before using the existing surface as a substrate. It is advisable to consider the need for a partial or full crack isolation membrane. Those methods are F125-Partial and F125-Full in the TCNA Handbook.

Any existing expansion in the substrate beneath the existing installation must be honored in the new installation. TCNA Handbook Method EJ171 will be the reference to all expansion and other types of joints that must be honored and designed and installed into the new system. Note that EJ171 states the architect shall specify the location of any expansion joints and other soft joints throughout the field and other locations such as the perimeter and any change in plane. Have the architect specify in writing (via drawings) where these are to go and which materials and EJ171 details should be used to construct them.

Checking for the ability to bond to the existing tile is imperative. If there are sealers or oils or waxes, etc., on the existing sur- face, they must be removed. If the tile is highly polished, it will likely require mechanical abrasion to allow the bond coat to adhere. I suggest doing a simple bond test by mixing and placing (including keying in) the mortar that will be used for the project onto the surface of the existing tile. Do this in several representative locations. Allow the mortar to cure for several days then remove it to determine how well it was able to bond to the substrate. You can select the trowel you will use for the job, comb the mortar and place a tile on top of the bond coat as a means of checking your coverage and inspecting the overall performance of the bond coat at the same time. Document everything about this test in writing and with photographs. Repeat the test with other materials and

tools if needed.
Depending on the results of the

bond test, it may be advisable to apply a primer that will facilitate bonding. Some setting-material manufacturers have specific primers designed for this purpose. They can recommend their best products (including mortar) for this application. I suggest using a system approach from one manufacturer that includes any primers, membranes, mortars, grouts, sealants, sealers, etc. I advise you to contact the technical representative of your preferred manufacturer about this job. They will be happy to assist you in writing a system warranty specific to this job.

Please also refer to ANSI A108.01 2.6.2.2 as an important reference for this installation.

It is necessary to ensure the substrate meets industry standard flatness requirements found in the ANSI Standards and TCNA Handbook. Please refer specifically to ANSI A108.01 2.6.2.2.

Generally speaking the standard is:

  • 1/4” in 10’ for tile with any side 
less than 15”
  • 1/8” in 10’ for tile with any side 
15’ or longer
  • Flatness can be checked with a 
10’ straight edge.

Financial allowances must be included in the specification, and proposal for labor and materials to flatten and otherwise prepare the substrate must be included in the specification and proposal. 
Tiling over sound existing tile as a substrate is an excellent way to proceed. As with any tile installation, careful research, proper planning, using the recommendations of industry standards, following manufacturer instructions, using a system approach, good communication and documentation before you proceed will mean a great and long-lasting installation and will make all parties happy with the end result. You are already on the right path. I hope this helps!

Mark Heinlein, NTCA Trainer/Presenter

Ask The Experts: July 2017

QUESTION:

I have a client with glass tiles cracking on an install. The GC admitted to not installing with a crack suppression membrane. They also drilled pilot holes for a door install that resulted in cracking. The tiles associated with the holes were installed before drilling. The final comment by the client was the cracking was from the back, and did not come through the face.

In your opinion, is it likely the lack of a crack isolation membrane created the opportunity for all of these tile cracks?

 

ANSWER: 

It appears to me that the crack at the window wall may be related to structural stresses within the framing or deflection in the substrate. The crack at the control valve may be related to structural stresses such as deflection within the substrate that was not well supported at the valve location. The cracks from the drill holes are likely related to the physical and heat stresses placed on the tile during the drilling process and may also be related to deflection in the substrate if the substrate was not well supported in this area. A crack isolation membrane would likely not have prevented the cracking.

There are other potential issues that can cause large-format glass tile to crack. They would include: Incorrect mortar or adhesive selection; mortar cure time (which will vary based on the mortar used and whether a waterproof membrane was used); thermal expansion from light or hot water; lack of expansion joints; deflection in the substrate; etc.
– Mark Heinlein,
NTCA technical trainer/presenter

QUESTION:

I’m dealing with customers who are unhappy about their recent tile installation. They feel the tile has too high a color variation. Could the installer have laid out the tile incorrectly? Whose responsibility is this – the installer’s, or mine? Thanks for your help.

ANSWER:

Per our conversation, on page 2 of the 2016 TCNA Handbook there is a section that deals with aesthetic classification. It specifically talks about variations in color, texture and appearance, and how tile suit- able for TCNA Handbook installations must meet specifications out- lined in ANSI 137.1. This ANSI standard sets performance and aesthetic criteria for many types of tile. Using tile that meets ANSI 137.1 ensures a degree of quality and consistency among tiles.

This chart from CTDA illustrates the ranking of shade variation levels, from the most uniformly shaded V1 to V4, which represents a tile with the highest degree of shade or color variation. A V0 tile is very uniform in appearance and smooth in color, with a color difference of less than 3 Judds when measured by a colorimetric spectrophotometer.

Tiles can have a V (variation) designation from V0 to V4. V0 tiles are very uniform in color and shade. V2, V3, V4 tile all increase in their randomness of color with V4 being the most random. Is the tile in question an ANSI 137.1 tile and what is its V designation?

The TCNA Handbook says that tile should be installed from several boxes in a random fashion to avoid aesthetic issues. Are you aware if the installer did this? How much was installed before the variations were noticed? How quickly did the installer report this to you?

It is common practice in our industry to report any defects or issues with the tile prior to installation. Many tile manufacturers even have disclaimers on their boxes explaining that claims against the tile must be made prior to installation. Let me know the answers to these questions and I will try to help you further.

– Robb Roderick,
NTCA technical trainer/presenter

 

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Q & A With NTCA Technical Trainer Mark Heinlein

Q:  We have 12 x 24″ and 12 x 36″ that weighs about 4lbs per square foot. We are installing on commercial bathroom walls in a brick layout. Is it standard practice or even necessary to put Hardie Backer Board up first to ensure the tile stays up? A tile installer said he could just install it right over the gyp board, and I disagree.
Please let me know what is regulation or expected for this kind of installation.

A: Here is some information to help you determine whether the gypsum board is the appropriate choice for this installation.

The installation of ceramic tile on gypsum board is detailed in TCNA Handbook Method W243.  As noted in the “Preparation by Other Trades” section of this method, it is very important that the gypsum board has been installed in accordance with Gypsum Association publication GA-216.

GA-216 (which further refers to GA-214) describes the installation details for gypsum board that is to receive a finished tile installation.  It specifies stud size and placement, fastening schedule, board thickness, whether a single or double layer is required and how the joints and fastener heads are to be treated. For example, the face layer joints should be treated with tape and one bedding coat of joint compound (no finish coats) and the fastener heads are to be treated with one coat only.  I suggest checking with the gypsum board installation contractor for this project.  They will be familiar with the requirements of GA-216 and GA-214 and able to tell you whether those requirements have been met on this particular installation.

In addition, the substrate flatness must meet the standard of 1/8” in 10’ for installation of large format tile to ensure proper bond coat coverage and a finished surface within tolerance for lippage standards.  (FYI – GA-216 and GA-214 include nominal tolerance requirements for in plane alignment of stud faces before gypsum board is installed.  This is critical to ensure a flat substrate meeting the 1/8” in 10’ for a large format tile installation is achieved.)

Since you are tiling in a commercial application, the Environmental Exposure Classification needs to be considered.  Method W243 provides a COM 1 (Commercial Dry) exposure rating.  That means this method is acceptable for tile surfaces that will not be exposed to moisture or liquid, except for cleaning purposes.  Examples of COM 1 exposure include: dry area ceilings; soffits; decorative/accent walls; corridor walls.  Commercial cleaning and maintenance practices typically generate greater water exposure than residential practices.

I suggest that a greater exposure rating for this area may be needed. You mentioned fiber cement backer board. Method W244F provides a COM 1, 2 or 5 exposure rating when fiber cement backer board is installed according to the requirements of the method.  COM 2 (Limited Water Exposure) is for surfaces that are subjected to moisture or liquids but do not become soaked or saturated due to the system design or time exposure.  Examples of COM 2 areas include some backsplashes and other walls such as bathroom walls and wainscots where water exposure is limited and/or water is removed.

I suggest speaking with the GC and architect or owner to determine what the expected environmental exposure for this bathroom is expected to be then select the best method to meet the need.  Either way, make certain the substrate is properly installed and prepared to receive the tile installation.  The flatness requirements of 1/8” in 10′ apply for all substrates to be used for installation of large format tile.

I hope this helps.

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