Tiling over a painted surface

QUESTION

I know the TCNA Handbook for Ceramic, Glass and Stone Tile Installation says that paint is not a recommended surface for tile installation but here is the situation.

I am doing a commercial job and did a wall of large subways. The owner was taken with the installation and has tripled the areas she now wants tiled. Of course she already paid for the drywall guys and the painter to finish these areas. What I should I recommend as best and acceptable course of action? Of course money is an issue.

ANSWER

Congratulations on having your scope of work triple in size.

Installing tile on gypsum board and painted gypsum board is always an intriguing question to consider. It is always best that the design and construction of the substructure and selection and installation of the substrate be done to meet the requirements necessary to support a tile installation.

As you already know, TCNA Handbook methods W242-18 (Organic Adhesive) and W243-18 (Cementitious Bond Coat) are for installing (direct bonding) ceramic or glass tile on a substrate of gypsum board fastened to wood or metal studs. In these methods, the Preparation by Other Trades section states: “Gypsum board… to be installed per GA-216.” and “Gypsum board face layer joints – treated with tape and joint compound, bedding coat only (no finish coats). Nail heads, one coat only.”

I break down (and paraphrase) those statements in this way:

  • Gypsum board is to be properly installed (by the gypsum board installation contractor) as described by the Gypsum Association’s GA-216 (which further references GA-214).
  • The face layer joints of the gypsum board are to be treated with (joint) tape applied to a bedding coat of joint compound.
  • Nail (fastener) heads are to receive one coat only of joint compound.
  • No additional finish coats of joint compound are to be applied (to the face layer joints or to the fastener heads).
  • These instructions say nothing about painting the gypsum board, which indicates it is not to be painted.

In other words:

  • The board is not being prepared for painting, papering or any other surface finish.
  • The board must be fastened and prepared to support a tile installation as the surface finish.
  • Additional considerations for a vertical tile installation on gypsum board include:
  • Weight of the installation
  • Deflection ratings
  • Flatness of the substrate

° For Organic Adhesive: Refer to ANSI A108.4. Substrate flatness tolerances are listed in ANSI A108.01 2.5.2.1 and ANSI A108.02 4.1.4.2.2. Additional flatness tolerances are listed in the TCNA Handbook Method W242-18 Preparation by Other Trades section.

° For Cementitious Bond Coat: Refer to ANSI A108.5. Substrate flatness tolerances must not exceed those required for vertical surfaces as defined ANSI A108.02 4.1.4.3.2 and as listed in the TCNA Handbook Method W243-18 Preparation by Other Trades section.

° See also TCNA Handbook Substrate Requirements on pages 30 – 33

  • Environmental Exposure

° Methods W242 and W243 are rated as Res1 (Residential Dry) and Com1 (Commercial Dry). See TCNA Handbook pages 44 – 47.

° See also TCNA Handbook Backer Board Selection Guide Direct Bond to Wood or Gypsum Wall Board – Caution on page 20.

  • Bonding the tile to the substrate

° For any installation, the correct setting material or adhesive must be selected to bond the tile to the substrate.

° In a gypsum board installation, the setting material or adhesive must bond to the paper face and joint compound.

° If the gypsum board has been painted, the paint is bonding to the paper and joint compound and the setting material must bond to the paint.

Finally, to get to your question, the NTCA Reference Manual contains a list of Questionable / Unsuitable Substrates (see page 30 in the 2018/2019 edition).

Paint is listed as a Questionable Substrate.

The NTCA Reference Manual advises: “Questionable substrates are substrate types that when properly designed and prepared can receive direct bond applications of ceramic tile and stone. Some questionable substrates conform to specific ceramic tile and stone industry installation methodology when applicable requirements are followed. In addition, the use of specific installation materials designed for unique applicant can result in a successful installation. Consult ceramic tile and stone installation manufacturers for their recommendations.”

What this means for your installation is, once it has been determined the gypsum board and its supporting structure have been properly designed, constructed and installed to support a tile installation, consult your setting-material manufacturer to determine which of their adhesives or mortars (and possibly primers) are recommended to bond the tile to the painted gypsum substrate. Obtain from them a job-specific written warranty covering the installation.

If you find the walls have not been properly designed, constructed and installed to support a tile installation, speak with the owner, general contractor and other trades to discuss what needs to be done to bring them into tolerance. Generally speaking, when you install the tile, you are accepting the substrate. If you need to re-fasten, prepare or render the substrate for flatness, make sure you have an approved change order to get paid for the work.

The NTCA Reference Manual goes on to say “Certain questionable substrate types can receive ceramic tile and soon installations when installed with a…. cleavage membrane/lath and plaster wall assembly.” This means another option would be to follow TCNA Handbook Methods W221 and W222 which can use the installed gypsum board as a solid base for a mortar bed installation.

Please watch this episode of Question Mark on NTCA’s TileTV that shows a commercial wall substrate that did not meet standards for a tile installation: http://www.iwantmytiletv.com/index.php?video=1B7E5CA9 or https://bit.ly/2T3f5AV

I hope this helps.
Mark Heinlein,
NTCA Training Director

Does this look like a troweling error or product defect?

QUESTION

Have you guys ever seen this before? It seems to be where the mesh is holding the tile together. This is a 2” x 4” glass mosaic (approximately a 12” sheet). I know this is asking a lot without actually seeing the install and product in person. Note the “voids” around the periphery of each piece of tile. Does this look like a troweling error or product defect to you? Please let me know. I’d love to know your insight on this.

 

ANSWER

You are correct – this is difficult to fully and accurately assess without being on site and personally inspecting an uninstalled tile, inspecting the completed installation and interviewing the installer.

However, based on the photo you sent I would hazard a guess that the anomalies we are seeing are uncollapsed ridges made with an approximately 3/16” V-notch trowel. 

Mark Heinlein
NTCA Training Director

Round drain or linear drain

QUESTION

We have a customer that set the drain back against a wall in a shower. It’s in California and it’s an outside shower. Shouldn’t this be a linear drain, or is it okay to have a 2”-3” drain against a wall? The pitch seems to be okay. The actual issue is people were slipping. It’s an outdoor shower for a community pool with older tile. We’ll be suggesting a tile replacement and, if they want to keep the existing tile, an epoxy coating option to help mediate the slip-fall issue. Thank you. 

ANSWER

You are correct in reasoning that a linear drain would likely be most appropriate for a shower drain placement that is very close to a wall. With a linear drain, the floor of the shower can be uniformly sloped in one or more flat / properly sloped planes toward the sides and ends of the drain. Having said this, the waste pipe needs to be carefully located and sized to accommodate the linear drain being used.

With a round drain, it may be more difficult to obtain the correct slope (minimum 1/4” vertical per 12” horizontal) consistent slope to drain. A typical round clamping ring drain and many round bonding flange drains may not be able to be positioned close enough to the wall to allow for proper waterproofing connections and/or slope to the drain. There may, however, be some round drains especially designed to work properly in close proximity to a wall while still allowing for proper waterproofing connections and slope to the drain and/or weep holes. 

Mark Heinlein,
NTCA Technical Director

 

Cracked and/or chipping polished and honed field tile

QUESTION

I am in need of your expertise. I have a client that installed Porcelain Statuario polished and honed 30” x 30” and 15” x 30” field tile in both a lobby floor and a dance floor of a country club. It’s quite a large area, so there were about 912 of the 30” x 30” tiles and about 132 of the 15” x 30” tiles, in total. About 80 tiles are exhibiting cracks and/or chipping (see pictures below). Any thoughts or ideas will be gladly welcomed.

ANSWER

It appears the failures in this installation may be caused by less than the standard requirement for bond coat coverage (80% in a dry area), and/or the tiles may not have been tested to or meet the ANSI A137.1 requirement for breaking strength, or something else that is not possible to determine from these photographs.

As a trade association representing tile contractors, NTCA is able to provide pre-installation technical assistance based on recognized American tile industry standards, methods and best practices. We are not able to provide detailed analysis or consultations for post-installation failures.

Given that this installation is already in place and is failing and the apparent high-profile setting of the installation I suggest that an on-site analysis and failure determination be conducted by one of NTCA’s recognized consultants, all of which can be located at this link: https://www.tile-assn.com/page/recconsultants. These consultants can perform a third party analysis and determine the cause(s) of failure.

I hope this helps.
Mark Heinlein,
NTCA Technical Director

Guidelines for installation of thin porcelain panels

QUESTION

I am looking for installation guidance for 30” x 60”, 1/4” thin porcelain panels in a floor application over concrete. It is a high rise building so I assume it is post-tensioned concrete assembly for the floors. Does TCNA have any guidelines?

Furthermore, the City of Minneapolis requires a sound damping product be used under hard surface flooring such as porcelain tile. 

While I have received information from one thin-panel distributor and from LATICRETE that this thin material should not be used over a sound control membrane, the architectural rep for the product manufacturer says their thin panel can be treated like any other porcelain tile. However, she will not provide any documentation that validates that statement. Can you perhaps help me get something from the manufacturer that sheds light on this question? 

ANSWER

There are several points necessary to discuss regarding your concerns.

Do you own a copy of ANSI A137.3 / ANSI 108.19? These are the material specifications and installation standards for Gauged Porcelain Tiles and Gauged Porcelain Tile Panels/Slabs. I refer to these as “GPTP” for short. This standard defines what GPTP is, where it can be used, how to properly install it and specifies the training required for persons installing it. If you do not own a copy of this standard, it is available for purchase from the NTCA’s bookstore at: https://www.tile-assn.com/store/ListProducts.aspx?catid=398904 or https://bit.ly/2oLCCsL. 

You are correct that any installation on a post-tensioned above ground slab will require special considerations. TCNA Handbook method EJ-171 addresses some of these concerns. It is the responsibility of the project’s specifier (i.e. architect, structural engineer, etc.) to develop the jobsite-specific drawings, material and installation specifications that will guide your installation. This includes details for movement joint placement. If these documents and clear instructions are not included as part of the statement of work or drawings, you need to request them.

ANSI A137.3 / A108.09 defines the “Gauged” (thickness) component of Gauged Porcelain Tile / Panels (GPTP) in two categories: 3.5mm – 4.9mm thick and 5.0mm – 6.5mm thick. The standard allows for installation of the thicker 5.0-6.5mm material on floors and walls. The 3.5-4.9mm thick material is for use on walls only (not floors). Some manufacturers will allow for the use of their thinner GPTP material on floors. I strongly recommend you make absolutely certain that you receive a jobsite-specific warranty from the GPTP manufacturer before installing thinner (3.5-4.9mm) tiles/panels on a floor.

Regarding use of a sound damping product under GPTP – ANSI A108.19 Section 3.0 (Existing Surfaces/Substrates) states in subparagraph 3.3 “Do not install over unstable, compressible surface materials or coatings.” I suggest contacting the sound reduction membrane manufacturer for more specific information for use of their product with GPTP.

Proper substrate preparation and selection and use of membranes and mortar and trowel and installation techniques are very critical for the successful installation of GPTP. Proper training for installation of this product is required by the A137.3/A108.19 standard. NTCA and product manufacturers provide this training for persons who will be specifying and installing the material. In summary, the specification should be very clear in referencing all industry standards for installation of GPTP. The GPTP and setting material manufacturers should provide you with a clear jobsite-specific warranty and installation instructions for use of their product(s). The installers are required to have training. If this is not the case, you will want to carefully consider your acceptance of risk with this installation. If the manufacturer cannot provide you a clear warranty, I would consider that a red flag.

I hope this helps. 

Mark Heinlein,
NTCA Training Director,
NTCA Technical Trainer

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

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