White marble turning yellow

Ask the Experts – September 2018

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 at [email protected]


QUESTION

I have a client whose installer used mastic to install white marble and now it’s turning yellow.

I looked in the TCNA Handbook, but could not find any information. Can you please guide me where it is mentioned?

ANSWER

ANSI A136.1 is the American National Standard Specification for Organic Adhesives for Installation of Ceramic Tile. It provides information for use of Type 1 and Type 2 organic adhesives for installation of ceramic tile. ANSI A108.4 is the Standard for Installation of Ceramic Tile with Organic Adhesives or Water Cleanable Tile-Setting Epoxy Adhesive.

The 2018 TCNA Handbook contains information about selecting the correct products to install natural stone in these locations:

  • The Natural Stone Selection Guide near the front of the book includes a subsection “Considerations When Selecting Installation Materials.”
  • The 2018 TCNA Handbook includes approximately 66 methods for installation of natural stone, including movement joint guidelines. To my knowledge, none of the installation methods for natural stone list organic adhesive as a suitable material for the bond coat. Typical bond coats detailed in the “Materials” section of the stone methods are cementitious or epoxy.

The TCNA Handbook’s Setting Materials Selection Guide (page 17 in the 2018 edition) includes a subsection for using “Organic Adhesive” in which it is described as suitable for setting ceramic tile.

As you have already discovered, organic adhesive is not identified as a bond coat for installation of natural stone tile. One of the reasons is the result experienced in the white marble installation that has yellowed.

I have found that some manufacturer’s technical data sheets for their organic adhesives specifically state they are not to be used for setting natural stone. I hope this helps. 

Mark Heinlein, NTCA Training Director, NTCA Technical Trainer

Caulking corners and Lippage issues

Ask the Experts – September 2018

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 at [email protected].


QUESTION

My biggest question is regarding plane intersections, specifically a corner where two vertical walls meet inside a shower. I know that we should be caulking – not grouting – the corner joint, but what’s the best way to go about doing this? Should we put in the backer rod prior to grouting and then remove the backer rod (if the joint is small enough to not need it) before applying the silicone? Otherwise, it seems to me that it is going to be tough to keep that joint clean of grout, and once the grout is in there it essentially locks out the ability for expansion, right? Or am I thinking about this wrong?

Also I’m hung up on lippage (no pun intended!), especially when using bigger (say 12˝ x 36˝ or 12˝ x 48˝) tiles. Even when not having any overlap in the pattern so as to minimize the potential for misaligned height differences between the centers and ends of the tiles, it seems to be very, very difficult to get a truly flat install even when using a lot of leveling spacers. I know that the lippage requirements increase based on the tile size, but what else can we do besides trying to keep the pattern helpful to minimizing lippage and spot-checking tiles and not using any badly warped tiles? Seems like a lot of waste that way too.

ANSWER

Your description in your first question is correct. ANSI A108 recommends grouting before installing sealant. Grout hardening in the change-in-plane joint is problematic. Installing the backer rod before grouting, then removing and replacing it is a good way to keep the joint clean. Use ASTM C920-rated silicone grout-color coordinating sealant for the joint. ASTM C920 sealant requires use of a backer rod for best performance.

For your second question – to begin with, as discussed in our workshops, substrate flatness for large-format tile is critical. Lippage tolerances do NOT increase with tile size. Layout, pattern and grout joint width are all components of minimizing lippage and keeping it within tolerances. All of these are standardized measures required by ANSI A108. Often, it is of crucial importance to use tile manufactured in accordance with ANSI A137.1 to achieve less-than-maximum allowable lippage in an installation. 

Mark Heinlein, NTCA Training Director, NTCA Technical Trainer

Ask the Experts – August 2018 – The Green Issue

Many people reading the Ask the Experts on page 22 in our June issue (and the TileLetter
Weekly Tuesday Tech Tip on July 3rd) were puzzled by an answer that appeared to a question about T&G boards. The problem was the answer addressed issues with porcelain planks and expansion joints, and it left a lot of people scratching their heads. 

We admit it, we had a bit of an email mix up and so the answer to a different question that originally appeared in the same thread was posted. This is the T&G board question paired with the correct answer:

QUESTION

I’ve got a new question for you all. What about homes with subfloors consisting of T&G boards, not plywood? They run diagonally. In this one specific case, there is actually 3/4” solid wood installed over the top of it. My thought is that it would require double 3/4” plywood, and I can’t find a single method in the book that identifies such a subfloor.

ANSWER

We get this question quite often. The movement between the planks can be too much for a tile installation. Most manufacturers require 3/4” OSB or plywood to install concrete board and uncoupling membranes for ceramic and porcelain tile installations. Installations involving stone require additional layers of plywood . 

You really have two options here: you can remove the existing layer of plank subfloor and replace with plywood, or add additional layers of plywood to the existing plank. Check with your manufacturer, but most will warranty the installation by adding an additional layer of 1/2” plywood before installing their product. Fasten down any loose planks, and sand or chisel down any high planks before installing your plywood.  Use the correct amount and type of mortar between the plywood and concrete board or uncoupling membrane. With concrete board installation use the right type and number of fasteners, stagger sheets from each other running them perpendicular to the plywood you have just installed. Depending on the thickness of the tile and underlayment there could be height differences between adjoining floor surfaces. These are somewhat common in older homes and can be handled with wood, stone, or even metal transitions. I hope this helps. 

Robb Roderick, NTCA Technical Trainer/Presenter

And here’s an excerpt from the question that prompted the answer about plank porcelain tile and expansion joints (correct answer follows):

––––––––––––––––––––

QUESTION

Wow. Just wow. There’s no way to make an expansion joint [with a long plank] look right. Zero chance. And I guarantee you 99% of every run over 25’ has no expansion joint filled with flexible sealant. I would love to see some installs from certified contractors who utilize them, if for no other reason than to generate ideas for placement and to show a customer what it will be like…Fortunately, most homes do not have that expanse because they’re doing single rooms or less than the whole house. It’s really only whole homes that are probably affected, so it’s a smaller subset.

But manufacturers keep making [planks] longer and longer, and they know the requirements. Without regard to installation requirements, they pump these things out at a cyclic rate, and customers have no idea. The average tile mechanic doesn’t either. And 9 times out of 10, incorrect installations rarely get held accountable, so when customers don’t want to listen to the right way and go get it done the wrong way, the competitor makes money, you don’t gain sales, and the customer is never the wiser. 

ANSWER

Attached are pictures of different installed tile work incorporating movement accommodation joints. The first is a residential installation with porcelain plank tile where a change of pattern is in a doorway to allow for a nearly unnoticeable movement accommodation joint. The other two are from commercial jobs where large areas of tile happen quite frequently.

In the TCNA Handbook from page 430 to 437 is section EJ171. It states under location and frequency of joints:

  • Interior – maximum of 25’ each direction Exterior- 8’ to 12’ in each direction
  • Interior tile work exposed to direct sunlight (heat) or moisture – maximum of 12’ each direction
  • Above ground concrete slabs – maximum of 12’ each direction
  • Perimeter joints – movement joints are required where tilework abuts restraining surfaces such as perimeter walls.
  • Change of plane, exterior – movement joints are required in all inside and outside corners.
  • Change of plane interior – movement joint required at all inside corners

Others and I believe it is the least used, most often misunderstood, and most important listing in our Handbook. Lack of correctly-installed expansion joints is thought to be – by many – the leading cause of failures in tile industry.

With plank installations, special considerations to layout should be considered. Installing expansion joints on the long side is easier, and less noticeable.

For example, if you have an installation that is 20’ x 80’ you would need a minimum of at least three joints perpendicular to the long wall creating four separate sections. Running the long edge of the plank perpendicular to the long wall would help hide these expansion joints, and would appear similar to a grout joint. Borders and change of pattern can also help you succeed in installing less-noticeable expansion joints.

Whether they are noticeable or not, they are required by our standards. If you look closely, you can find expansion joints in almost every airport, shopping mall, car lot, etc. There are great installers implementing the standards found in EJ 171 all across the country.

The TCNA Handbook says “The design professional or engineer shall show the specific location and details of movement joints.” If they don’t, reach out to them for information. If it’s just you and a homeowner, show them what the industry says in our standard and create a plan for a successful installation. 

Robb Roderick, NTCA Technical Trainer/Presenter

Ask the Experts – July 2018

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 at [email protected]


QUESTION

I have these photos from a customer who is adamant that the chipped tiles are defective. The tiles are butted up and were installed without grout. Would the inability to allow deflection be the cause of breakage?

ANSWER

You are correct. These tiles have very likely chipped along the edges where they touch each other because an appropriate grout joint was not installed in the system. 

Appropriately-sized grout joints are required by tile industry standards and are an integral component to successful tile installations. One of the purposes of a grout joint and grout is to protect the edges of the tiles from damage such as this. 

Mark Heinlein, NTCA Training Director, Trainer/Presenter

QUESTION

Have you seen a rise in issues with tile crazing? I’ve had several issues with a few different factories with different dye lots. From both Italy and Spain, all glossy. ALL of these jobs used one form of waterproofing; all used premium thinset and premium grouts. All of the factories pass the crazing test and also ANSI. Without seeing into the walls, the jobs looked solid, very good craftsmanship. I have had a total of seven jobs with this issue (three of one color – two dye lots. Four others in all different colors and lots). I figured job complaints would go up with the amount of ceramic tiles that are sold but this seems like an issue that maybe needs an installation adjustment? Looking forward to your thoughts.

ANSWER

I have done some checking and discovered one similar job that was having a crazing problem. On that job, actual tiles from the lot that had been installed were tested and found to not actually meet the ANSI requirement for crazing resistance. I suggest having tiles from the actual, installed lots tested to determine whether they actually pass the ANSI and/or ISO tests for crazing as indicated by the factory. The tests will be able to determine if there is proper fitment of the glaze to the tile body.

The Tile Council of North America (TCNA) operates an independent laboratory that can do this testing for you. Katelyn Simpson is the laboratory manager and can provide information on cost and the testing procedure. Katelyn can be reached at (864) 646-8453 or [email protected]

Depending on test results, you will be able to contact the factory with detailed information to discuss resolution. 

Mark Heinlein, NTCA Training Director, Trainer/Presenter

Ask the Experts – June 2018

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 at [email protected].


QUESTION

I’ve got a new question for you all. What about homes with subfloors consisting of T&G boards, not plywood? They run diagonally. In this one specific case, there is actually 3/4” solid wood installed over the top of it. My thought is that it would require double 3/4” plywood, and I can’t find a single method in the book that identifies such a subfloor. 

ANSWER

Attached are pictures of different installed tile work examples incorporating movement accommodation joints. The first is a residential installation with porcelain plank tile where a change of pattern is in a doorway to allow for a nearly unnoticeable movement accommodation joint. The other two are from commercial jobs where large areas of tile happen quite frequently. 

In the TCNA Handbook from page 430 to 437 is section EJ171. It states under location and frequency of joints:

  • Interior – maximum of 25’ each direction; Exterior – 8’ to 12’ in each direction. 
  • Interior tile work exposed to direct sunlight (heat) or moisture – maximum of 12’ each direction. 
  • Above ground concrete slabs – maximum of 12’ each direction. 
  • Perimeter joints – movement joints are required where tilework abuts restraining surfaces such as perimeter walls.
  • Change of plane, exterior – movement joints are required in all inside and outside corners.
  • Change of plane interior – movement joint required at all inside corners.

Others and I believe this is the least used, most often misunderstood, and most important listing in our Handbook. Lack of correctly installed expansion joints is thought to be – by many – the leading cause of failures in tile industry.

With plank installations, special considerations to layout should be considered. Installing expansion joints on the long side is easier, and less noticeable.

For example, if you have an installation that is 20’ x 80’ you would need a minimum of at least three joints perpendicular to the long wall creating four separate sections. Running the long edge of the plank perpendicular to the long wall would help hide these expansion joints, and would appear similar to a grout joint. Borders and change of pattern can also help you succeed in installing less-noticeable expansion joints.

Whether they are noticeable or not, they are required by our standards. If you look closely, you can find expansion joints in almost every airport, shopping mall, car lot, etc. There are great installers implementing the standards found in EJ 171 all across the country. 

The TCNA Handbook says, “The design professional or engineer shall show the specific location and details of movement joints.” If they don’t, reach out to them for information. If it’s just you and a homeowner, show them what the industry says in our standard and create a plan for a successful installation. 

Robb Roderick,
NTCA Trainer/Presenter

Ask the Experts – May 2018

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 at [email protected].

QUESTION

I recently installed 2” x 2” sheet-mounted mosaics in a public park bathroom. During the tile installation the general contractor provided me with limited lighting. Electricians installed LED light fixtures above and against the wall. 

During the installation, the owners of the facility were very pleased with how the product looked on the walls. But I noticed that with these very bright lights located directly over the tiles, you could see imperfections. Plus, shadows from the lighting made the tile job look like it was not done well, but when you ran your hand against the tiles you could feel that it was done properly. 

A couple of months later they contacted me for a meeting to go over the installation of the tiles because they felt it was unacceptable. When I arrived the owners went over some of the areas and claimed that I did not do a good job. I did notice some tiles that needed to be replaced, but for the most part they were installed very well. I told the owners that I do not have a problem going over quantities that needed to be replaced and that I would take care of it; we even went to another facility where a different installer installed the same type of tile but the light in that room was not directly against the wall and you could not see the cast shadows – but when you ran your hand again the wall you could feel the imperfections. The bottom line is that the owners want me to replace the whole wall, which it is not necessary to fix the problems. I also documented during the process pictures that the drywall was not properly installed and leveled, and that was another reason for the imperfections. 

Can you provide to me or help me with some sort of literature or a reference to a handbook so I can protect myself from being taken to court? Clearly this issue is because of the way the lighting fixture is located and how it casts shadows, making the installation unacceptable. I did find some information about this topic but I do not know how to approach this to avoid court. 

ANSWER

The situation that you have found yourself in is very common to our industry. We have received several technical calls about the influence of lighting on finished tile work. The design community has embraced this type of lighting to give a more dramatic lighting effect. Any type of lighting located on or near tile walls accentuates irregularities by casting shadows on the tile surface.

The good news is, our industry has addressed this issue in several places: in the TCNA Handbook, page 34; in the NTCA Reference Manual from page 121 to 127; and in the ANSI standards on page 26.

There are allowable amounts of lippage in any tile installation. There are charts in both the ANSI standards and TCNA Handbook based on the type of tile, tile size and joint width. Attached is an image of Flatness and Lippage table on page 36 from the TCNA Handbook, versions 2017 and 2018 (image courtesy TCNA).

In summary, our standards say that the angle of light cast on tile work can accentuate otherwise acceptable variance.

We have had members bring lights in to a situation like this, taking photos of the same wall under two different lighting influences. This can be dramatic and show the impact lighting has on the appearance of a installation. Attached is an image from the NTCA Reference Manual showing the same wall with two different lighting options.

As far as the surface not being flat enough to start with, there are standards for how flat a surface should be to install tile. The surface should have no deviation (hump or dip) of more than a 1/4” in a ten foot radius. As far as the substrate not being correct and affecting the installation, this should have been addressed prior to the installation. Once we start an installation we have accepted the substrate as suitable. Once we start tiling a surface
we now own it. 

Robb Roderick,
NTCA Trainer/Presenter

Ask the Experts – Coverings 2018

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 at [email protected]

QUESTION

I will begin by letting you know that I have 25 years in the industry with tons of training and on-the-job experience. 

I have multiple showers having crazing. The crazing is starting to happen a few weeks after installation and it is all over. All are installed with cement backer board, roll-on waterproofing with premium thinset and grout. No structural issues are evident.

I’m using good quality ceramic tile imported from three factories. I have sold a couple of million square feet of tile and I have gotten maybe one case of crazing a year, but now I am seeing it very often. Are you hearing this also? Are there any new recommended installation procedures? 

Even though I am importing a container at a time of each color with the same lot, 99.99% turn out fine, and then crazing appears on isolated jobs. Looking forward to some input.

ANSWER

It sounds like you purchase and install a significant quantity of these tiles. Have you contacted the tile manufacturers? Have you compared lot and run numbers from cartons of tile used in the failed installations? Perhaps the manufacturer(s) have had some issues with application of some glazes to certain tile bodies in certain lots or runs that could correlate to the failures you are experiencing.

Have the tiles been manufactured to ANSI A137.1 specifications?

Do you know whether the tiles have been tested to meet or exceed ASTM C424 for Crazing Resistance? This is a destructive test performed on tiles that meet ANSI A137.1 Specifications for Ceramic Tile. In this test, tiles are subjected to 150 psi steam pressure. Tile samples that pass the test show no evidence of crazing. Refer to ANSI A137.1, subsection 6.2.3.6.

Do you know whether the tiles have been tested to meet or exceed ASTM C484 for Thermal Shock? (ANSI A137.1, subsection 6.2.3.7)

As far as recommended installation procedures, it sounds like you are employing a version of TCNA Handbook methods B415 or B421 or B422 with a cement backer board and a liquid, surface-applied waterproofing membrane. Do you suspect any of the concerns listed below may exist in the installations that are exhibiting crazing?

  • Proper / improper installation and cure time of the liquid waterproofing membrane
  • Excessive bond coat thickness
  • Proper / improper cure time prior to grouting
  • Change in plane movement joint installation

You mentioned you are not able to determine the quality of the framing or whether there is deflection in the substrate. Are you able to learn from the building’s owners or building records whether there is wood or metal framing and whether the framing on the failing installations was properly braced to support a tile installation?

Was the board properly gapped between sheets at horizontal and vertical joints, filled with Portland cement mortar and taped with alkali-resistant mesh tape? Were open joints left between the boards where they meet at inside corners to allow for movement at the change in plane?

As you can see, I have more questions for you than answers at this point. Some, or a combination of the items described above may have an effect on the system performance. I suggest starting with the tile manufacturer and determining whether the tiles have been tested to ANSI A137.1 specifications and if there may be a correlation or concern with the lots that are failing.

Ask the Experts – March 2018

QUESTION

I am a homeowner having a glass tile install performed. The tile is a 3” x 12” glass subway tile with a color backing. It is being installed as the backsplash around the stove/oven. My tile contractor said to butt the glass tiles up to each other with no spacing in between – and to butt them up to the quartz countertop – but I was told by the tile store to use a 1/8” spacing.

All I am looking for is your technical opinion on the proper way to install the tiles regarding the spacing to give some instruction to my contractor for the install. The tile edges/corners are flat with no bumpers that would cause a spacing when they are butted up to each other.

ANSWER

We always encourage our members to follow the guidelines set forth in the TCNA Handbook. On page 37 of the Handbook it states “that in no circumstances shall the grout joint be less than a 1/16 of an inch.”

One of the reasons listed for a minimum requirement for grout joint size on all tile installations is “thermal expansion.” Glass tile is highly expansive. It also explains that the grout joint should be no smaller than three times the variation of the tiles themselves. That means if a particular group of tiles vary in size 1/16”, the smallest grout joint recommended for that particular group of tiles is 3/16” of an inch.

Most glass tile manufacturers have directions for the use of their products. I would encourage you to contact the manufacturer of the glass to get their recommended grout joint size. And make sure there is the appropriate sealant joint where ever the tile meets differing materials like a countertop or cabinet.

I hope this helps.

Robb Roderick, NTCA Technical Trainer

QUESTION

I plan to have a small bathroom tiled, shower walls with niche, shower floor, and floor (12” x 24” walls and 4” hex all floors). This is on concrete slab.

I’m working with a contractor who is bringing tilers in for the job and I’d like to make sure they are following standards. Can you tell me what the acceptable methods are for building/waterproofing a mud-pan, including shower wall and threshold?

I know they are creating a mud pan, but not sure what products or method they are using. I’m assuming there are a variety of products used and methods, which makes it complicated for the lay person. Any information/diagrams are appreciated.

Thank you!

ANSWER

You are correct that shower construction is complicated. It is critical that a shower is constructed properly.

Depending on the specifics of your installation, there are several methods for constructing showers published in the 2017 edition of the TCNA Handbook for Ceramic, Glass and Stone Tile Installation. These will guide a contractor who owns and uses them.

These methods include: B414, B441, B415, B420, B426, B431, B421, B422, B421C, B422C. These methods may vary somewhat depending on whether ceramic/porcelain or stone tiles are being installed. In addition, the Handbook contains several details for common configurations for curbs and membrane installation.

You are also correct that there are a variety of products on the market that are excellent for constructing successful shower and tile installations. Many of these materials meet or exceed the ANSI A118, ANSI A137.1 and ANSI A137.2 standards. A knowledgeable installer and contractor will be able to identify the appropriate materials and relate them to the TCNA Handbook method that is most appropriate for your installation.

If your contractor is a member of the National Tile Contractors Association I would be happy to speak with them and assist them with any questions or concerns they may have in selecting the appropriate method for constructing your shower. If your contractor is not a member of the NTCA, I would be happy to speak with them about becoming a member, and all of the professional benefits membership provides. A search for an NTCA member contractor near you can be done at this link: http://tile-assn.site-ym.com/search/custom.asp?id=2759 or http://bit.ly/2FJiak6.

I highly recommend employing a Ceramic Tile Education Foundation (CTEF) Certified Tile Installer (CTI). CTIs are installers who have proven their knowledge of skills in applying industry recognized standards, methods and best practices to ensure you get the correct installation from the substructure to the finished tile surface. CTIs can be located at this link: https://www.ceramictilefoundation.org/find-certified-tile-installers or http://bit.ly/2CSu5Jf.

I hope this helps!
Mark Heinlein – CTI #1112, Training Director,
Technical Trainer / Presenter

Ask the Experts – February 2018

QUESTION

We found the stress cracks in the floor several days after the tile was installed. I had never seen anything like this in my 40 years of being in the trade, and neither had my tile man. They showed up as slightly wavy white lines in the marble. There was not a black line or crack you feel.

We removed a couple of tiles where two stress cracks intersected. The tile was well bonded to the 1/2” cement board below the tile. There was no intersection of sheets of cement board below the crack. The cement board looked sound. We removed the cement board to expose the tongue-and-groove plywood subfloor below. Where the cracks intersected in the floor was exactly where a sheet of plywood stopped and started. The cracks lined up with long 8’ run and one 4’ run. So, somehow whatever movement took place in the sheet of plywood transferred up through the cement board to the tile. There were no cracks in the cement board and it was firmly bonded to the plywood.

We took up all the tile and cement board. We checked the subfloor with a laser to see if the floor was showing any signs movement. The entire floor was within 1/8” of level everywhere we checked. There were no ridges in the plywood where the sheets butted together. The only suspicious thing I found was an area along the 8’ side of the plywood where the tongue of one sheet was not fully engaged in the groove of the other. This meant that there could be more flex in the plywood than there should have been.

We removed the sheet of plywood and checked the framing. The new joists we sistered onto the existing joists were 2” x 8”. They were nailed soundly to the existing 2”x 10” that were all over 2” thick. These joists spanned from the living room wall to the exterior wall. They also pass over the wood columns and beams that divide the stair well from the entry hall. The floor platform was really strong and robust. The plywood had been installed with construction adhesive and ring shank nails. It was fully bonded to the framing and very difficult to remove.

We could not see any good reason why the tile came to show the stress cracks. The only reason that I could come up may have had to with using adhesive to bond the plywood to the framing. I have seen problems in other areas due to adhesive shrinking as it dries. We have found when wall board is installed with adhesive and screws that the screws and plaster above them can show up as little humps on the surface of the board as the adhesive dries and pulls the wall board closer to the framing. It is only a fraction of an inch but I have seen this happen many times before – as the board moves closer to stud and the screw stays fixed, you get a hump.

This is only a theory but if the plywood got pulled tighter to the framing as the glue dried, could that small shift in the floor sub floor cause the crack in the tile? Total guess.

Also the non-fully-engaged tongue could have had something to do with it on the long side. Though short side of the ply was firmly seated on a joist, and we had stress crack here, too.

Marble is much softer than other stones or porcelain tile. Like I said before, I have never seen this happen before and we have used this type of assembly successfully for many years.

Anyway, we decided to add rows of blocking between the joists along the 8′ length to make sure that side of the plywood was more secure. We re-installed the plywood and were planning on using uncoupling membrane under the tile to avoid further stress cracks in the marble.

I suggested to the client that he might like another type of floor material to avoid any other chance of this happening again due to the softness of the marble. I understand everyone’s reluctance to do this, but I just wanted to increase our chances of having no further complications.

The tile installer feels pretty confident the uncoupling membrane will do the trick. My stone guy examined our tile and he said the product was as sound as you are going to get with Carrara marble.

What do you think?

ANSWER

Good to hear from you. As you are aware, the NTCA always encourages people to follow industry guidelines set by both the Tile Council of North America (TCNA), and American National Standards Institute (ANSI).

I was able to read the correspondence about this stone tile failure. The questions raised are covered in our industry standards.

The assembly that failed was a backer board installation over plywood. Attached is the diagram from the TCNA Handbook method F250, which is the closest method to what was described. If you notice two layers of plywood are required underneath the backer board install. For a similar installation using ceramic only one layer of plywood would be required. That detail is found in method F144 on page 162 of the 2017 TCNA Handbook.

There are two standards for allowable deflection in tile installation. For ceramic and porcelain tile, the standard is L/360. For stone tile installation the standard is L/720.

The L in this equation is the length of unsupported span under the installation in inches. This means that only half of the movement which would be allowable with a ceramic install would be allowable with a stone installation.

The question about adhesive under the plywood against the floor joist is addressed in ANSI A108.11 it states “…a 1/4” bead of construction adhesive should be applied to the center of the top of the joist and the plywood fastened to joist with 6d ring shank nails. There should be a 1/8” gap between the subfloor sheets.”

There was a mention of using an uncoupling membrane for the second installation. A second layer of plywood is required when using uncoupling membrane. Check with the uncoupling membrane manufacturer for complete instructions on this type of installation.

I hope this information helps. – Robb Roderick, NTCA presenter/trainer

Ask the Experts – January 2018

QUESTION

I’m having issue with glass tile for one our customers. We’re trying to determine what’s causing the cracking. I believe it might be due to the thinset shrinking. Is it possible that it may be the tile?

ANSWER

Yes, it is possible that the glass cracking could be due to thinset shrinkage as it cures, especially if the maximum bond coat thickness of the thinset was exceeded. But looking at the two photos you sent, here are my guesses.

In the first photo that includes the glass door and hinge, it appears that the glass may potentially have cracked from:

  • over-tightening of the screw through the hinge
  • a minor misalignment of the hole drilled in the glass to accept the screw
  • weight of the door on the fastener at the pressure point if all components of the door installation were not properly aligned or balanced.

In the second photo showing the closeup of the grout joint, it is difficult to know what caused these small fractures. The photo is taken too close to see a context of the location in the shower. It appears that the photo was taken very close to the glass and the fractures are fairly small. My guess is the fractures may have been in the tile at the time it was installed and they weren’t noticed by the installer.

If you need a solid determination of these fractures, a third party consultant that can make an onsite evaluation may be needed.

I hope this helps.

Mark Heinlein – CTI #1112, NTCA Training Director, Technical Trainer / Presenter

QUESTION

We are members of NTCA and would love some technical advice on thin panel installation.

We are supplying large-format, thin porcelain panels for an exterior façade in Oakland, Calif. It is approximately 2,500 sq. ft. at 102˝ x 47˝ x 6.5mm and we are researching installation options for the owner that do not involve the normal setting method.

It would be great to know what options there are for a “rail & clip” system versus full contact installation.

At the very least, it would be great to get some information on the guidelines and practices for installing thin panels using some sort of clip or fastening system.

ANSWER 1

Thanks for contacting us. I took a quick look at the manufacturer’s instructions. They are very typical of most gauged porcelain tile panel manufacturers. I did not see anything other than the direct bond method as an option for installation. Most distributors of thin porcelain tile have been working with installation product manufacturers and tool companies to present a system approach to installation. Some even require the use of manufacturer trained installers.

Last April there were new standards added for this product. ANSI 137.3 and ANSI 108.19.

ANSI 137.3 deal with standards for the product itself. ANSI A108.19 deals with the installation of the product.

I would encourage you to reach out to the manufacturer to see if they would recommend another fastening system. We always encourage our members to follow manufacturers’ instructions explicitly. It decreases your liability in projects.

Robb Roderick, NTCA Trainer/Presenter

ANSWER 2

Thank you for contacting our NTCA Technical Team with your question.

Robb is correct. ANSI A137.3 and ANSI A108.19 are the industry standards adopted this year for the production and installation of gauged porcelain tile and panels/slabs. These standards call for the installation of this material in a thin-bed type system with special emphasis on the installation process for floors and walls outlined in A108.19.

As Robb stated, it is important to follow the tile manufacturer’s instructions. Contact them to be sure you understand their instructions thoroughly. Deviation from installation instructions can result in lack of warranty coverage and/or acceptance of risk by the installation contractor.

The Tile Council of North America (TCNA) has the new standards available on its website for electronic download and it is taking pre-orders for a limited-edition hard copy. You can find the information to purchase an electronic version or reserve your hard copy on the TCNA website www.tcnatile.com/products-and-services/publications/218-english-publications/227-ansi-a137-3-and-a108-19.html or http://bit.ly/2i4iP4p.

Local codes will likely have specific requirements for installing tile above a certain height, especially on an exterior.  Please be certain to contact the code official responsible for the municipality this installation is located in.

Many setting material manufacturers make specialty mortars for installation of these tiles.  You will want to involve your setting material manufacturer to help you determine the best mortar for the application and ask them to work with you to write a site-specific system warranty based on their instructions and industry standards.

I am not aware of any mechanical rain-screen type fastening systems for use with gauged porcelain tile/panels; however, some tool and equipment manufacturers make a clip-type system that is used in conjunction with a thin-bed bond coat installation to provide additional mechanical attachment of large tiles in a vertical installation. One such system is manufactured by Raimondi. For more information about that system please contact Donnelly Distributing/Raimondi USA at 262-820-1212 or [email protected]

Mark Heinlein – CTI #1112, NTCA Training Director and Technical Trainer/Presenter

1 2 3 9