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Are Credit Card Grout Joints Specified? Check Tile Industry Standards.

Are Credit Card Grout Joints Specified? First Check Tile Industry Standards.

Yes, credit card joints - as in grout joints the thickness of a credit card - are popular, but given tile industry standards, they aren't possible, appropriate, or even recommended.

Many installers have had customers who have seen tile installations in a magazine or brochure which is exactly what they want in their homes. Unfortunately, the “look” they want to achieve with credit card thickness grout joints most likely will not be possible using the tile that has been selected.

Let's explore why.

All About Credit Card Joints Table of Contents

How Does Tile Selection Affect Grout Joint Size? 

Will Natural Tile Accommodate Credit Card Grout Joints?

What about Calibrated Tile and Credit Card Joints?

What About Rectified Tile and Credit Card Joints?

What is Rectified Tile?

Why Rectified Tile Makes Smaller Grout Joints Possible

Comments and Questions from Readers

What Does a Poor Credit Card Grout Joint Look Like?

Tile and Radiant Heating Systems 

Cutting Tile Correctly 

How Do You Use Tile Industry Standards?

How Does Tile Selection Affect Grout Joint Size? 

Depending on the dimensional consistency of the tile selected, and if it was tested to the requirements of the American National Standard Institute (ANSI) A137.1 specification, the size of the grout joint can be determined.   

Under the A137.1, tiles fall under one of three categories: 

  • Natural tiles are packaged directly after manufacturing and are not sorted by size. 
  • Calibrated tiles are sorted after production to meet a specific size range.
  • Rectified tiles are taken from the production line and mechanically finished.  

>> See ANSI Standards: A Tile Installer's Best Friend!

Will Natural Tile Accommodate Credit Card Grout Joints?

The simple answer is no.  Since natural tile is not sized or sorted after the manufacturing process, the size range can vary significantly making it impossible to even consider a thin grout joint.

What about Calibrated Tile and Credit Card Joints?

If the customer selects a calibrated tile which, according to the ANSI A137.1 Specifications, can contain tiles that range in size within a defined tolerance in the various sized tiles in the same box, for the project and requests that the grout joint be the thickness of a credit card (1/32”), the installer will have a very difficult if not impossible task. 

Using such a narrow grout joint with tiles that vary in size could have two larger tiles side by side that actually touch each other with no grout joint, while two smaller tiles side by side could show a grout joint of over 1/8” or more (four times the requested 1/32”). 

This is where another ANSI specification, A108.02- 4.3.8, defines the required minimum grout joint size. 

“To accommodate the range in facial dimensions of the tile supplied for a specific project, the actual grout joint size may, of necessity, vary from the gout joint size specified.  The actual grout joint size shall be at least three times the actual variation of the facial dimensions of the tile supplied. 

Example: for tile having a total variation of 1/16” in facial dimensions, a minimum of 3/16” grout joint shall be used.  Nominal centerline of all joints shall be straight with due allowances for hand-molded or rustic tiles.  In no circumstance shall the grout joint be less than 1/16”.

As per the above example, a tile with just a 1/16” variation in size requires that the grout joint be 3/16”, which is significantly wider than the consumer desired 1/32”.

What About Rectified Tile and Credit Card Joints?

Let's start with defining Rectified Tile.

What is Rectified Tile?

As Sal DiBlasi explains in this 1:28 minute video titled Rectified Tiles Explained, rectifying tile ensures that the overall tile size is more precise.



Rectification does not affect the thickness of the tile, only the edges. That means rectified tile is better suited for situations where thinner grout joints are desired. 

>> See What is Rectified Tile and Why Does It Matter for Your Tile Installation? for closeup images of rectified and non-rectified tile.

The rectification process grinds the edges of the tile to achieve a more precise facial dimension.  The grinding makes the sides parallel to each other and sized to a specific dimension such as a large format plank tile as seen in the photo below.

How Does Tile Selection Affect Grout Lines?

When using these large format tiles, another ANSI guideline applies. ANSI A108.02 – in part states:

"Tiles (square or rectangular) with any side greater than 15 inches (as are the tiles in the photo), the grout joint shall be, on average, a minimum of 1/8” for rectified tiles and, on average, a minimum of 3/16” wide for calibrated (non-rectified) tiles."

Why Rectified Tile Makes Smaller Grout Joints Possible

When your customer selects a rectified tile, the opportunity for a successful tile installation using smaller grout joints is much greater.  Why? Because the rectified tiles provide more precise facial dimensions.

Installers need to know these specs and use these details to their advantage.  Allowing a consumer to dictate the grout joint size without regard to these industry guidelines, is a recipe for failure which can lead to a disaster. 

Knowing and understanding these guidelines can help you guide your clients to an acceptable grout joint size and eliminate these problems from your job sites.

Comments and Questions from Readers

Since publishing this article, we received several questions and comments that Scott responds to.

What Does a Poor Credit Card Grout Joint Look Like?

Rebecca Pultorak comments as follows:

"Clear, excellent explanation. Can you add photos of what a poor credit card grout joint on non-rectified tiles looks like? (vs. a rectified one?) It would be a helpful visual for clients.

Also, what would the job look like years down the road? Is there tenting where two non-rect tiles butt (structural issues, flooring failure) or is it just aesthetically dirty in joints that couldn’t be filled properly with grout?"

Here's Scott's response:

If you look at the photo below, you can see everything you requested and one additional problem with this type of installation.  Almost all of the tile is installed using what is known as tight, butt, or NO joint. 

As I stated above, this type of installation is not appropriate or recommended. Most of the tiles are touching which causes two problems:

  • One is the two chipped tiles
  • Second is that it is extremely difficult if not impossible to install grout into the joint. 
The tile in the upper left corner does exhibit an “almost” credit card joint (1/32”), but again if the grout can be worked into the joints, it most likely will crumble out in the future.  The grout manufacturers recommend a minimum 1/16” joint which is twice the width of the credit card thickness of 1/32” joint.

Tenting (when the tile arches upward) is caused by the lack of movement accommodation (expansion) joints in the system.  The floor shown in the photo did have the necessary movement joints, but it exhibited some structure deflection problems which allowed the floor to move up and down.  With the tiles actually touching each other, the pinching motion of the deflecting floor caused the glaze to sheer from the body of the tile. 

As the photo shows, this trick does not work and should not be used under any circumstances.  Nuf said?

What Does a Poor Credit Card Grout Joint Look Like?

Tile and Radiant Heating Systems 

David Ribeca asks:

"My question has to do with Method RH123-13 and RH116A-13 in the TCNA Handbook.

I do not have the latest issue these numbers are from a 2013 handbook. I have a job coming up in the near future that has two rooms one is the kitchen which is on wood framing 16" on center 3/4 plywood heated basement, the adjacent room to this kitchen is a concrete slab on grade with insulation under the slab. I suggested both floors in these areas to have the methods I noted above. These floor areas to be tiled were sunk 2" below existing finished wood floors.

We established the rough floor height after removing the old slate floors that were originally installed in this area 12 years ago. The job has been in limbo until now. We completed the work in the rest of the house and left this area for a later date. Between now and then there have been numerous builders and architects brought in to complete these areas. After 12 years of getting estimates and job costs from other contractors, the homeowner finally called back the original contractor and me to complete the project.

The homeowner, new architect, and HVAC contractor installing the heat tubes originally wanted to install the plywood boards with grooves and sheet metal on them on the wood structure then have me install cement backer board and tile over that. I refused to because it is not an approved method. Their original plan for the concrete slab was to just encapsulate the pipe in cement totally on top of the existing slab and I refused that method as well. No one is following the guidelines set by the TCNA for this installation except for me.

The newest issue from the HVAC contractor is a thermal break on the slab with 2" of foam then the heat tubes were installed. The existing floor elevations we are trying to meet will not allow for the foam then cement and tile on top of the slab. Furthermore, I refused that as well, I have seen no mention of a thermal break in the handbook.

The HVAC contractor also wants to install sheet metal on the wood structure to reflect the heat up into the room. I saw no mention of this in the Handbook. Just primer and plastic lath. I understand that the architect should be the one designing the whole floor heat system as well as the tile installation based on job site conditions. I have told the homeowner I would not be responsible for the design and function of this floor. All I have done up to this point is suggest the right way to install the floor tile and heat tubes based on the guidelines the TCNA has provided. It seems to me the HVAC people do not have a clue as to how to install their product for the best tile installation possible based on job site conditions.

This is not the first time I have run into this issue around here. I have never seen a job where the floors were properly prepped for the added height needed for this type of install. Most of the HVAC contractors want to use the plywood boards with the grooves in them then cement board and tile.

When the TCNA makes their guidelines do they also pass this information along to the Hydronic people so everyone is on the same page with these installs???? It kind of makes it difficult for me to sell my knowledge based on what information I was given for the correct installation method based on job site conditions.

The HVAC contractor, their suppliers, and or the manufacturers of their product should have the proper information as well for a proper installation of tile and or stone over their product based on job site conditions. They all seem to know one method the grooved plywood with cement board installed over it.

I went way off track here the main issue for me right now is how do I tell the HVAC guy he’s wrong; none of his installation methods are approved installation methods? As the Tile Installer, How do I know if these thermal breaks are required for his system to work properly?? How do I know if there needs to be sheet metal on the plywood deck for his system to reflect up toward the tile install? There seems to be a lack of communication between all parties involved in this whole system why??? No one is ever on the same page."

Scott responds as follows:

I am not certain I can accurately answer all of your questions due to some contradictory information, but I will give it a shot.

The 2019 issue of the Tile Council of North America (TCNA) Handbook includes sixteen radiant heat details including the ones you mentioned (RH123 and RH116A).  However, none of them include the grooved plywood/reflective metal system you described.

Your suggestion that the heat system manufacturers and the TCNA collaborate on approved systems would be helpful to the installing tile contractor.  But realize that the TCNA Handbook methods are tested and have been deemed appropriate by the Handbook committee for tile installations over some (not all) types of heat source.   Likewise, the heat system manufacturers create, test, and approve methods that work well for their purposes.  Unfortunately, they are not designed to work in concert with each other.

The bottom line?  If you are not comfortable with combining tile and heating systems that lack tile industry recognition and recommendation……. walk away.

For additional perspective, here's an article relating to radiant heating: How to Install Tile with Electrical Radiant Heating.

Cutting Tile Correctly 

Kathy Steigerwald asks this question:

"If I have a marble mosaic tile what tool should be used to cut it? It seems the contractor we hired can't cut the tile correctly--it keeps falling apart. Thanks, Kathy"

Scott explains,

Most natural stone mosaics, which include marble, are back-mounted on a glass fiber mesh using an adhesive.  Unfortunately, most of these adhesives are water-sensitive and release when they become wet, which is the issue your installer is experiencing.  

There are two ways to approach this situation. 

  • The first is to cut the mosaic sheets to get the majority of the full tiles mounted on the sheet located on the substrate.  Then, cut the individual pieces on a wet saw and hand-set them where needed.  This is not the most ideal method, but it does work. 
  • The second method would be to use a dry cutting saw which is equipped with an OSHA-approved dust containment system.

How Do You Use Tile Industry Standards?

Your goal as a qualified tile contractor is to communicate to customers how tile industry standards affect the success of a tile installation.

As desirable as a credit card joint may be to your customers, using tile industry standards to educate them will demonstrate that there is a better way to complete a high-quality tile installation that will stand the test of time.  When your customers realize you know your stuff and you don’t waffle on these established methods and best practices, they should thank you for providing options that eliminate a possible failed installation. 

If you haven't already, consider becoming a Certified Tile Installer (CTI). As a CTI, you set yourself apart from the crowd and know how to anticipate tile installation problems before they occur. Do it right the first time and get paid accordingly.

If you're looking for a qualified installer, be sure to use the CTEF zip code locator to find a CTI near you so you get it done right the first time.

Also, visit The Tile Installation Experience with Scott Carothers at Coverings.

Thanks for reading.


Prevent Problems: Read the Homeowner's Guide  to Hiring a Qualified Tile Installer


Note: We originally published this article on February 6, 2018, and have updated it.