Working with face and mesh mount sheet mosaics

It is not breaking news that tiles are made in all colors and shapes and sizes and thicknesses and materials. They each have their own beauty, and tiles of all types and sizes are regularly mixed together to create stunning installations with purpose and function that stand the test of time when properly engineered, specified, designed and installed.

Installation spotted at a public market in Seattle, Wash. 

This article focuses on installing mosaic tiles that have been pre-assembled into a pattern on sheets of mesh, paper or plastic.  But first, a little information about mosaics. 

What are mosaics?

The American National Standard Specification for Ceramic Tile (ANSI A137.1) defines ceramic mosaic tile as: Tile, usually 1/4” to 3/8” thick, and having a facial area of less than 9 square inches. Such tiles are typically mounted in sheets or strips with other mosaic tiles.

Where do mosaics come from?

Many tile manufacturers create mosaic tiles for one-of-a-kind and general pattern installations. The tile industry has a host of notable tile artists who create one-of-a-kind hand-crafted mosaics. By their nature, many tile installers are craftspersons with artistic skills. The Tile Trade Artisans Guild Facebook group is dedicated to encouraging artistry in the trade. Visit it at www.facebook.com/groups/tiletradeartisansguild

How are mosaics mounted?

Artisan created and installed one-of-a-kind mosaic. Photo courtesy of Dragonfly Tile & Stone.

Mosaics can be edge-mounted. Flexible glue is applied to the tile edges, leaving the back of the tile open for full contact with the bond coat. Paper or plastic can be applied to the face of the tile leaving the back open for full contact with the bond coat.

It is important to note that when mesh is applied to the back of the tiles it will become an integral and permanent part of the tile installation. There must be sufficient openings in the mesh netting to allow for adequate, direct contact of the bond coat to the back of the tile. If mesh mount tiles are to be installed in an exterior, wet or submerged installation, the mesh must be suitable for exposure to water.

A common concern with installers is how straight or crooked the mounted mosaics are. It can be tedious work to straighten crooked tiles that are stuck to a sheet. For readers interested in acceptable variations of mosaics mounted to a sheet, open up your copy of ANSI A137.1, study Table 6 and read section 9.5 Test Method For Mounting Variations.

How are mesh and face mount mosaics installed?

First, examine your substrate. Is it flat? If not, stop the installation and start the conversations that lead to making the substrate flat. Is there a membrane in place? This will affect cure time, especially for glass mosaics and plastic face-mounted mosaics.

Proper bedding procedures: For an outstanding description on how to properly bed mosaic tiles (set into mortar), pull out your 2019/2020 NTCA Reference Manual and read pages 108 – 110.

Mesh and face mount mosaic installation instructions:

  1. Check the substrate for flatness.
  2. If the substrate is not flat, make it flat. (Attend an NTCA Regional Training program to learn the skills, tools, and materials to do this.)
  3. Check the area to be tiled for squareness.
  4. Calculate the best, most defensible layout and consider the primary focal point and use. (Attend NTCA virtual and in-person workshops to learn how to do this. For more information, read the Training & Education story in this issue.)
  5. Apply a grid system for the layout to follow.
  6. Clean the substrate.
  7. Dampen dry substrates.
  8. Mix the mortar, following manufacturer instructions.
  9. Key the mortar into the substrate with the flat side of the trowel.
  10. Use the gauged side of the trowel to apply more mortar.  Hold the trowel at a consistent 45-degree angle and trowel the mortar into straight ridges.
  11. Prime the trowel by applying a ridge of mortar along the length of the flat side of the trowel.
  12. Hold the primed trowel at a shallow angle then drag it, flattening the ridges to create a consistent, bond coat layer consistently 3/32” to 3/16” thick (approximately).
  13. Set the tile into the mortar.
  14. Use a solid, flat trowel, float, or similar tool to embed the tile into the freshly troweled bond coat layer. Press well enough to ensure a minimum bond coat of 80% (dry areas) and 95% (wet areas) without forcing excess mortar into the grout joints. Bond coat coverage percentages are for each individual mosaic tile. Pull some tile to check for coverage. Change your trowel size if needed. Practice your technique.

Mesh mount-specific instructions:

  1. After setting the tile and making sure bond coat coverage is achieved, align the tiles to ensure there are no sheet lines.
  2. Insert the long, clean edge of a straight, flat trowel into the joints and use it to align the mosaics within the sheet and align the joints from sheet to sheet. A soft grout float can also be used to shift the tile.
  3. Stagger sheets as you install them to blend the grout joints from sheet to sheet.
  4. Cut squares or rectangles from sheets to overlap sheets as you install them, blending grout joints from sheet to sheet.
  5. Step back from your work and take photos of small sections as you set them. Sheet lines can be much more visible in a photo than when you are focused up close. Examining your work in this way as you go allows you to see sheet lines that you couldn’t while setting and make adjustments while they are freshly set.
  6. Use hard shims, spacers, wedges, or apply tape to the surface to hold tiles in place while they cure.
  7. After curing, clean squeeze-through mortar before grouting and applying sealant at movement and expansion joints and changes in plane.

Paper face-specific instructions:

  1. After setting the tile and making sure bond coat coverage is achieved, align the tiles to ensure there are no sheet lines.
  2. Stagger sheets as you install them to blend the grout joints from sheet to sheet.
  3. Cut squares or rectangles from sheets to overlap sheets as you install them to blend grout joints from sheet to sheet.
  4. Allow the set tiles to cure in place for 15 to 30 minutes (depending on the paper and adhesive).
  5. Apply a damp sponge to the paper face to moisten it and hydrate the glue that holds it to the face of the tile. Don’t get it so wet the paper will fall apart. Don’t let it be too dry so the paper tugs tiles out of alignment while you remove it. Practice.
  6. Pull the paper from one corner or edge of the tile at an angle across the face of the sheet until the paper is off. If the tiles shift or pull out of the mortar – allow the mortar to cure longer and try again. To reduce the amount of pulling force, try using a knife to slice the paper into smaller sections and pull along the short side of the section.
  7. Adjust individual tiles as needed. Insert the long, clean edge of a straight, flat trowel into the joints between tiles and use it to align the mosaic.
  8. Step back from your work and take photos of small sections as you set them. Sheet lines can be much more visible in a photo than when you are focused up close. Examining your work in this way as you go allows you to see sheet lines that you couldn’t while setting and make adjustments while they are freshly set.
  9. Use hard shims, spacers, wedges, or apply tape to the surface to hold tiles in place while they cure.
  10. After curing, clean squeeze-through mortar before grouting and applying sealant at movement and expansion joints and changes in plane.

Plastic face-specific instructions:

  1. After setting the tile and making sure bond coat coverage is achieved, align the tiles to ensure there are no sheet lines.
  2. Stagger sheets as you install them to blend the grout joints from sheet to sheet.
  3. Cut squares or rectangles from sheets to overlap sheets as you install them to blend grout joints from sheet to sheet.
  4. Allow the set tiles to cure in place until firm. Usually at least overnight.
  5. CAUTION: The plastic on the face of the tile will cause a longer cure time for the mortar.  Many mortars cure through the grout joints. Because the
    plastic covers most of the grout joints, the mortar will take longer to cure.
  6. Pull the plastic from one corner or edge of the tile at an angle across the face of the sheet until the sheet is off.
  7. Clean squeeze-through mortar before grouting and applying sealant at movement and expansion joints and changes in plane.

I hope to see your next mosaic installation posted on NTCA’s social media channels! Have fun tiling and I’ll see you next time!

The Hazards of Hybrids

Hybrid Shower

Today’s tile installations enjoy a tremendous amount of flexibility and creativity in methods, materials, and design. While a few decades ago there was only one option for waterproofing shower stalls, today we have myriad options. One tempting method is the Franken-shower, or hybrid shower system. But what risks are there and when is it the appropriate choice?

What is a hybrid?

With topical applications like B421 and B422 in the TCNA Handbook for Ceramic, Glass and Stone Tile Installation, which call for an ANSI A118.10 load-bearing, bonded, waterproof membrane, the membrane extends continuously from the drain to above the showerhead.

A membrane can either be sheet-applied or liquid-applied. Typically, a sheet-applied membrane calls for a 2” overlap at seams, corners, and penetrations. This is usually a band of the same material applied with thinset or an approved adhesive. A hybrid system is a liquid-applied membrane at corners and seams to create the waterproof overlap.

Some contractors who use this method do so simply because they don’t trust the science behind thinset bonding a 2” overlap to maintain a waterproof seal. The internet is replete with videos of contractors conducting their own tests to determine whether or not a system or material is actually waterproof. Other contractors prefer the ease of liquid-applied membranes over a seam. Still, others don’t like the potential build-up of overlapping membranes.

Trust the methods and manufacturers

Photo of hybrid seam installation
Hybrid seam installation. Photo courtesy of Bryan Cook.

That said, one of the most valuable resources we have available to us in the tile industry are ANSI standards and TCNA methods. When we use materials that meet ANSI A118.10 we can trust they will perform as a waterproof system. This being the case, we can and should trust the manufacturers when their materials are installed correctly. And in the TCNA Handbook, we find this language regarding the installation of waterproof membranes: “Bonded waterproof membrane must be continuous, including at changes in plane. Follow membrane manufacturer’s requirements for corners, seaming, and overlap.” Emphasis is mine.

Let’s take a closer look and see what challenges and risks tile contractors take when they build a hybrid shower system.

You don’t know what you don’t know

The first potential issue tile contractors should be aware of is introducing technical unknowns into the system. Potential material incompatibilities may arise when mixing waterproofing systems and materials. 

As contractors, we simply can’t know for sure how different materials will interact with one another. The liquid might require a mechanical profile to grab onto, or the sheet might not allow the liquid to integrate fully into the fabric, thus potentially allowing water to migrate behind the liquid membrane, leading to a failure. Since we can’t speak to the composition of the different materials and how they’ll interact, care should be taken in mixing components from different manufacturers. Ask yourself the following: If there is a failure, where would the fault lie? In the liquid seam? Or in the fabric material? How could that be determined? 

In this case, the failure, and liability, would lie squarely on the shoulders of the installer.

It’s worth noting that some manufacturers allow for a liquid seam mixed with their sheet membrane.  Since they are able to test in a laboratory setting, they can confirm the suitability and compatibility of these installations in their systems. This is key to deciding if a hybrid approach is the right one for your installation. If you prefer building your shower systems in this way, choose a system designed for it.

Partnering with a manufacturer benefits your client

The second issue you should consider is what the manufacturer recommends. A huge strength of our industry is the partnerships between installers and manufacturers. Our trade benefits from the support and knowledge that is available to each and every one of us. Following the recommendations of the manufacturers of the products we use is the simplest step we can take in our partnership.

A popular sentiment and statement is “my word is my warranty.” Unfortunately, it is not that simple. When companies write warranties, they are binding legal language. In other words, if you meet the terms of a warranty, they must as well. And these companies want to partner with us, and so they want to make sure you and your client are taken care of. Manufacturers want to stand with you behind their product. Often, manufacturers’ reps will even go beyond what’s required of them by the terms of the warranty to help installers in the field and to educate them. Of course, as noted above, that may be the start of a long-term partnership between the company and you.

Consider this: in 2020 we suffered an economic shutdown that could not be avoided due to COVID-19. Many small businesses went under, as they could no longer afford to stay in business. Others encountered health issues associated with our trade and must retire early or change careers. If in two years, a client needs a repair on their shower, but their installer is no longer in operation, who will they call? If they believe their shower was built as a system and is under warranty, they will call the system manufacturer. When the manufacturer comes to inspect the installation and determines that an unapproved hybrid system was “designed” by an installer who is no longer in business, what recourse will the homeowner have?

All this is to say we have an ethical obligation as professionals to our clients to make sure that not only is their shower built with proper methods, but proper materials as well. If we “design” our own hybrid system out of materials we happen to like, not only are we assuming all liability on ourselves, but we are actively voiding the client’s warranty, robbing them of their legal rights.

These are vital questions you should ask yourself:

  • Are you introducing technical unknowns into the system, and with them potential failures and health risks for your client?
  • Are you actively voiding your client’s warranty?

Perhaps this won’t change your mind on the subject. However, the fact remains that hybrids come with their own sets of hazards and risks.

Update! Respirable Silica Compliance

Hi everyone. I know you are all out there staying healthy, wealthy, and wise by following your local, county, regional, state, and federal guidelines to protect you, your employees, and your customers by preventing that pesky COVID-19 virus from finding its way into your lungs. This made me think this would be a great time to update you on the current state of compliance with OSHA’s Respirable Airborne Silica regulation. Just like COVID, you don’t want those tiny silica particles to build up in your lungs.

Here it is: There is no change.

That’s right. No change – yet. As I’m sure you know, the gears of government sometimes grind slowly, which seems to be happening with this regulation. In my experience, this usually means that those in charge of a program are taking a long, careful look before making changes to regulation while people are getting familiar with it.

cPaul Regina, TCNA’s Government Affairs Senior Specialist
Paul Regina, TCNA’s Government Affairs Senior Specialist

I recently checked in with TCNA’s Government Affairs Senior Specialist Paul Regina. Here is what Paul had to say about the state of the regulation:

There has been very little happening on the silica front.

In August of 2019, OSHA issued a Request for Information (RFI) regarding revisions to construction Table 1. The OSHA website says they are currently analyzing the data received during the RFI.

The current Unified Regulatory Agenda, an outline of when agencies believe they will be issuing regulations, indicates there is a Notice of Proposed Rulemaking dated June of 2020. Please see the following links for further information:

OSHA Silica Page: https://www.osha.gov/dsg/topics/silicacrystalline/

Silica in the Regulatory Unified Agenda: https://www.reginfo.gov/public/do/eAgendaViewRule?pubId=201910&RIN=1218-AD18”

As Paul noted, the primary item being looked at is Table 1. This is where the regulation lists the tasks that can produce varying amounts of respirable airborne silica. Table 1 is too long to include with this article, but you can review it for yourself here: https://www.osha.gov/laws-regs/regulations/standardnumber/1926/1926.1153

Let’s take a simple look at Table 1. It has these three columns: 

  1. Equipment/Task
  2. Engineering and work practice control methods
  3. Required protection and Assigned Protection Factor (APF)
  • An Equipment/Task is something you do or a tool you use to perform a task in the process of installing tile. A common example is a wet saw used for the task of cutting tile.
  • An Engineering and work practice control method is the description of how the tool is used to perform the task in a manner that keeps the silica dust at a certain level.
  • The Required respiratory protection and APF column is broken into two parts. Fewer than or equal to four hours per shift, and greater than four hours per shift. Each column will list an APF number ranging from 0 (none) to 25. You add up the APF numbers for all the tasks you do in a shift to come up with a total APF.

Here is one example of how the table works: 

Apprentice installer using engineering controls to perform the task of cutting tile with a saw that has a built-in water delivery system to control or eliminate respirable airborne silica. No mask required.

For the Task of cutting tile, if you use an Engineering and work practice control method of using a saw that came with a built-in water supply system designed to constantly keep the blade wet while cutting (a wet saw), you can run that saw and cut tile with it for the whole shift without wearing a well-fitted, approved face mask designed to keep the tiny silica particles from entering your lungs. See if you can tell how I put this example together when you view Table 1 yourself. 

There is so much information on the OSHA website about this. You really should check it out. The FAQ section is really good. It lists the questions that you and I both have and provides us with answers that aren’t loaded up with too much of that wonky government regulation language. You don’t have to be a safety engineer to figure this stuff out. OSHA is trying to help us all understand.

If you read nothing else, read this direct quote from the OSHA website. Even if you’ve read this before, it’s worth reading again. I know it gets my attention when I am not thinking about this every day.

Crystalline silica is a common mineral found in the earth’s crust. Materials like sand, stone, concrete, and mortar contain crystalline silica. It is also used to make products such as glass, pottery, ceramics, bricks, and artificial stone.

Respirable crystalline silica – very small particles at least 100 times smaller than ordinary sand you might find on beaches and playgrounds – is created when cutting, sawing, grinding, drilling, and crushing stone, rock, concrete, brick, block, and mortar. Activities such as abrasive blasting with sand; sawing brick or concrete; sanding or drilling into concrete walls; grinding mortar; manufacturing brick, concrete blocks, stone countertops, or ceramic products; and cutting or crushing stone result in worker exposures to respirable crystalline silica dust. Industrial sand used in certain operations, such as foundry work and hydraulic fracturing (fracking), is also a source of respirable crystalline silica exposure. About 2.3 million people in the U.S. are exposed to silica at work.

Workers who inhale these very small crystalline silica particles are at increased risk of developing serious silica-related diseases, including:

A tile contractor and installer really should think about respirable airborne silica during every work task they do every workday on every worksite. I’ll guess that you don’t have to think too hard to come up with the tasks that create the single largest amount of respirable silica. That’s right – dry cutting tile or grinding tile or mortar with a grinder that does not have a shroud and dust collection system that includes a 99% efficient vacuum and filter or fixed water supply system.

Many talented installers are doing amazing scribe-type tile work these days. Be sure you are using a saw or grinder with the right water supply-type or shroud and dust collection-type system to avoid breathing in respirable silica. (Photo courtesy of Stoneman Construction LLC)

I see a lot of very talented installers doing amazing scribe-type tile work these days. If you aren’t using a saw or grinder with the right water supply-type or shroud and dust collection-type system, then please think about the task you are performing. Think about what you are breathing in. It’s not COVID-19, but once those tiny silica particles get in your lungs they are never coming out. They are going to keep building up and will eventually make you sick and can even be the cause of what ends up killing you.

If you haven’t yet become familiar with OSHA’s Occupational Exposure to Respirable Crystalline Silica regulation 29 C.F.R. § 1926.1153, here is what you need to do for you and your company:

  1. Check out NTCA’s website and read up on the information and follow the links we have provided to the professional tile community. https://www.tile-assn.com/page/PositionStatLibrary, towards the bottom of the page. 
  2. Download our standard compliance plan.
  3. Create your plan.

After you do that, the rest will follow and will become part of your daily safety habits and work practices.

During an informational session at Total Solutions Plus last year, I had the opportunity to ask an OSHA staff member involved with putting the regulation in place if there is a distinction between commercial or residential contractors and whether they were inspecting residential contractors for compliance. He replied that all contractors and jobsites are subject to inspection. He continued that if they happen to see a residential jobsite under work, they may check to see how things are going. 

At any worksite, the first thing they will ask is to speak to the Competent Person and to see your company’s Respirable Silica Control Plan. What is a Competent Person? A Competent Person is an individual in your company who knows all about respirable crystalline silica and your control plan. This is the person who identifies respirable crystalline silica hazards on your jobsites and who has the authorization to correct them right away.

Want to know why this is important? They figure if you have taken the time to prepare a plan and assign a Competent Person, then you have probably looked at your tasks, work practices, and engineering controls, and calculated your APF and many of the things necessary to comply with the regulation designed to protect you, your employees, other trades, your client, and anyone else who enters your jobsite.

Respirable silica exposure control information available on the NTCA website.

Not only is it the law, but it’s also important stuff for your health and wealth. Be wise, take the time today to review your plan or make a plan. And enter “OSHA” at tileletter.com to keep up to date with the latest announcements issued by OSHA throughout the year.

Thanks for reading. Remember to join NTCA’s training team at a virtual live Program in a region or time zone near you soon. Go to www.tile-assn.com and click on the Education and Certification section to see all of the training programs available to you. I hope you take advantage of these terrific benefits today!

Why you need movement joints

Quick and easy ways to achieve them correctly

Hopefully, as a tile installer, you’ve heard a lot about movement, expansion, or movement accommodation joints – and regularly plan them into all of your installations. Unfortunately, too many people who regularly install tile are not aware of their importance. We’re going to explore why they are absolutely necessary – and how to provide them correctly, quickly, and easily. 

The National Tile Contractors Association (NTCA) Reference Manual glossary, provides this definition of an expansion joint (aka movement joint): “A joint through the tile, mortar, and reinforcing wire down to the substrate.” 

An unfortunate example of tented tile. The really sad part of this situation is that the installer did an excellent job, except for the lack of any expansion joints.

By integrating these “stress relievers” into the tile assembly, expansion and contraction takes place without compromising its integrity. But who is responsible to make this happen?

Sadly, movement joints are probably the least-used, most-misunderstood, and often-eliminated part of a tile installation. However, they are one of the most important listings in the Tile Council of North America (TCNA) Handbook under Method EJ171. Without movement joints, failure is lurking in the shadows, waiting to strike. This is true especially on floors with ceramic, porcelain, glass, and natural stone tile that is subject to sunlight, in-floor heat, and/or moisture. Many installations that appear to be well done, will fail. The lack of movement joints gives the tile assembly no room to expand, causing the tile to pop up or “tent,” most times in the middle of the floor. You must allow for this movement in all residential and commercial projects. Movement joints are not optional – they are required.

What the TCNA Handbook says about movement joints

The 2020 edition of the TCNA Handbook EJ171 Movement Joint Guidelines for Ceramic, Glass and Stone clearly states: “The design professional or engineer shall show the specific locations and details of movement joints on project drawings.” 

Regrettably, many people involved in the installation of tile products don’t understand that installed tile moves. If this expected movement is not accommodated, the tile will become rebellious and most likely will become very expensive for the responsible person or company.

In other words, as a tile installer, it is wise to include movement joints on every project. Again however, it is not the installer’s responsibility to design and/or locate these joints. That is to be done by the design professional or engineer.

The attached TCNA Handbook EJ171 detail shows the necessary components of the movement joint:

  • Width that is four times the expected movement
  • Compressible back-up
  • Rounded back-up with no bond to the sealant
  • The depth of the sealant is one half of the width of the joint

I call your attention to the sealant. Notice that the sealant is attached only on the sides of the two adjacent tiles.

The sealant attached to the sides of the tile is able to accommodate in-and-out motion like that of an accordion or a back and forth motion similar to rubbing two hands together.

One critical point here is that the sealant does not contact or bond to the sides and/or bottom of the joint. If the sealant is allowed to do so, it is locked in place and will have zero movement ability. In this case, the insertion of a “Rounded Back-Up,” or closed-cell polyethylene foam backer rod allows the concrete floor to expand and contract, but its primary role is to keep the sealant where it belongs: attached only to the tile edges. 

You will notice that the detail refers to the joint material as sealant. This is done purposely to differentiate it from lesser-quality caulking products (acrylic latex or siliconized latex), which dry hard and do not allow for continuous flexibility. According to the requirements of EJ171 and ANSI A108.01, this sealant must be 100% silicone, urethane or polysulfide.

If you understand these principles and install the joint properly, it will permit the required movement to take place, keeping the tile flat on the floor where it belongs. Certified Tile Installers understand this and can properly install movement accommodation joints.

Quick and easy methods for installing movement joints

Do you think movement joints are complicated or are messy to install? Actually, they aren’t. Here are two methods that will produce excellent results, easily and quickly.

Method #1 for movement joints:

Evaluating a Certified Tile Installer hands-on test, Carothers checks the inside corner of a wall to determine if the movement joint was properly installed. These joints provide the ability for movement to occur between wall to wall and floor to wall applications. 

Install the appropriate-sized foam backer rod into the joint

  • Apply painter’s tape along the tile edges of the joint
  • Fill the joint with 100% silicone
  • Smooth it with a sealant tool, popsicle stick, or plastic spoon
  • Remove the tape by pulling it on an angle toward the joint as soon as the sealant is in place.

Method #2 for movement joints:

  • Insert the appropriate foam backer rod into the joint 
  • Fill the joint with 100% silicone sealant (no need for tape)
  • Spray the sealant and the face of the tile with a mixture of water and dish detergent.

The sealant tool, popsicle stick, or plastic spoon is also sprayed with dish detergent solution, allowing the excess sealant to be easily removed without the worry of it sticking to or smearing on the face of the tile. This technique is something that Certified Tile Installers have to successfully complete during their hands-on test.

Depending on the type of joint specified, the profile of the smoothing tool can provide a joint which is either concave (as shown) or flat.

When should the sealant be applied?

ANSI A108.02 – 4.4.5 states, “Install sealant after tilework and grout are dry. Follow sealant manufacturer’s recommendations.”

As I conduct demonstrations on the proper installation of sealant joints, I often hear this statement, “It can’t be that easy.” It is really that easy. Using this technique will save time, eliminate costly callbacks, make your installers happy, and yield satisfied customers. Sometimes something so simple can provide huge rewards.


The Ceramic Tile Education Foundation (CTEF) provides education and installer certification for professionals working in the ceramic tile and stone industry. Certification programs include the CTEF Certified Tile Installer (CTI) program, that is the only third-party assessment of installer skill and knowledge to be recognized by the tile industry, and the Advanced Certifications for Tile Installers (ACT). CTEF is headquartered in Pendleton, S.C., near Clemson University and the TCNA offices. For more information, visit www.ceramictilefoundation.org.

Marble moisture discoloration: don’t blame the stone!

Carrara marble moisture discoloration on shower floors is a common problem that has been experienced by many professional tile and stone installers in the U.S. Cases when white or light-colored stone gets random, blotchy-looking dark spots are often posted and discussed at social media groups and online forums. The lack of technical information on cause and prevention of the above-mentioned problem seems to result in a rapidly-growing rejection of white marble as a finish suitable for wet areas. Stone is often blamed for its “poor quality,” “inappropriate mineral composition” and, thus, its inability to provide predictable results when it is installed on shower floors.

Such opinion is often based on the fact that light-colored marble is subject to moisture discoloration not only in cases when a tile and stone mechanic does obvious installation mistakes such as failure to provide proper pre-slope and/or final slope to drain, clogged weep holes, or not fully collapsed mortar ridges, but also in situations when the installer strictly follows the above-mentioned requirements.

This provides a controversy in the light of the fact that white marbles have been successfully used for wet room applications – for example in Europe – for a long time.

Ten Carrara shower modules were tested, with help and support from many industry professionals. Results showed that most of the problems with light-colored marble arise due to inappropriate installation methods/techniques that often result from the insufficiency of the technical information on this subject.

The research has helped to determine two main methods that, if properly followed, will provide great results for white marble at shower floors.

Method #1: traditional dry pack mortar bed shower pan

Before the surge of the discussed problem in late 2000s, marble was mostly installed in shower floors with a traditional water-in water-out system. A dry-packed mortar bed, consisting of one part Portland cement to four to five parts sand, not compacted too tightly and not finished too smoothly, provides a subsurface of connected and very high porosity allowing water to quickly be “taken away” from the underside of marble mosaic. If stone is bonded to substrate with a basic thin-set mortar (preferably unmodified due to its higher porosity), grouted with a simple grout, has no adhered fiberglass mesh reinforcement (an impervious coating on the back of stone also known as “resin backing”) and is not treated with an impregnating/penetrating sealer, the water absorption, migration and evaporation should not face extra complications. The above-mentioned shower system will provide exactly what it was designed for – a proper water evacuation, both topically and internally. 

Method #2: bonded waterproof membrane shower pan with epoxy adhesive and grout

According to our reasonable testing, the bonded waterproof membrane method also provides great predictable results with translucent stone like marble when it is properly installed with a suitable epoxy adhesive, epoxy grout, and very permeable (breathable) impregnating sealer. While the “dry pack” system enables great drainage and internal water evacuation, the second method provides marble with a highly hydrophobic/water-repellent subsurface, almost waterproof grout joints, and a reduced-to-minimum presence of moisture inside its pores, which enables relatively quick topical water evacuation, evaporation of moisture, and drying of the stone.

The problem with bonded membrane pan systems installed with modified mortar and grout

Integrated bonding flange drains create a little dam around the drain opening; not what you want in your marble tile shower installation. 

It is important to understand that the reduced porosity of modified mortars and many modern “stain-resistant” grouts – as well as the design of integrated bonding flange drains (that creates a little dam around the drain opening) within a bonded waterproof membrane system – not to mention the application of penetrating/impregnating sealers – do not contribute to proper internal water evacuation and evaporation. Water still penetrates the stone mosaics, whether sealed or unsealed, either as liquid or gas/vapor and moisture gets trapped below and/or inside stone. 

Saturation of the anchoring fleece in the top layer of a waterproof sheet membrane or dampening of the cementitious coating of a foam pan only reinforces the moisture discoloration. The close distance from the waterproof membrane to the stone on shower floor with a thin layer of mortar – that is much less porous than dry pack sand – does not allow water to be “taken away” from the underside of stone. If the shower is used somewhat moderately, marble and its subsurface do not get really saturated and can dry relatively quickly. However, if the shower is used “heavily” (for example, by a few people in a row), the chances of stone/mortar/membrane saturation are much higher, causing a gradual moisture entrapment within the shower floor assembly installed with the topical waterproofing method.

All the bonded membrane Carrara modules were constructed with full mortar coverage and 2% slope to drain and only one – installed with the “epoxy” method – has shown incredibly quick drying time (from two to three hours to return to the original light color). Other modules, whether sealed or unsealed, have all shown some sort of moisture discoloration that would not fully go away for days.

Trapped moisture under the translucent glass tile installed over a bonded membrane pan.

Again, the reason for such discoloration is the inability of a bonded membrane system to “hide” moisture entrapment under translucent stone when it is installed with materials that still absorb moisture and are not as highly water-repellent as epoxy. 

This conclusion is indirectly supported by the following remarkably interesting statements found in the TCNA Handbook in regards to translucent glass tile installation: “Bonding translucent glass tiles directly to membranes or other impervious surfaces is not recommended because any moisture trapped between the tile and membrane would be visible. Membranes should be placed behind or below the tile setting substrate where translucent glass tile will be installed” (TCNA Handbook for Ceramic, Glass, and Stone Tile Installation 2019, page 7)

The research on the subject continues. Next step will be testing eight new Carrara marble modules installed with different products within the two above-mentioned methods (“dry pack” and “epoxy”).

The INS and OUTS of layout

When we analyze the results of the Certified Tile Installer (CTI) test, given by the Ceramic Tile Education Foundation, we can see that when individuals fail, it’s most commonly because they are unable to complete the test in the allotted time. Often, that’s because so much time was spent trying to determine layout, and those that struggled with their layout simply did not have time to complete their module.

In real-world situations, layout is essential for achieving a pleasing, even design. In either case, there is definitely a need for training on tile layout. The NTCA’s newest workshop program is designed around this theme, and these are a few of the topics we will be addressing in that new training.

ANSI and TCNA layout guidelines

Both ANSI and the TCNA give us guidelines for layout; this information can be found in ANSI A108.02 Section 4.3, and in the TCNA Handbook section “Field and Installation Requirements.”

Tile layouts should be centered and balanced, like this one, if possible. 

ANSI directs us that:

  1. Tile layouts should be centered and balanced, if possible.
  2. We should not have an excessive number of cuts, with no cuts being smaller than a half tile when possible. 

The TCNA Handbook suggests the same but gives us a variety of situations where these guidelines may not be the best option or even possible in some scenarios. Examples of these are:

  • Considerations of focal points around decorative elements.
  • When the size and configuration of the room and the size of the tile make it impossible to center the layout in all aspects. 
  • Layouts that are continuously flowing to several spaces.
  • The effect the tile layout will have on waste.

Minimum grout joint size  

Another important section concerning layout in the TCNA Handbook addresses minimum grout joint width. The trend in our industry is for larger tiles to be installed with smaller grout joints. The guidelines in the TCNA Handbook can help installers to defend against customers who want smaller than acceptable grout joints or no grout joints at all.

A 1/16” grout joint is the smallest grout joint ever recommended. The minimum allowable grout joint size varies depending on the tile in use and how much one tile differs from another in size. The TCNA Handbook states, “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 grout joint size specified. The actual grout joint size shall be at least three times the actual variation of facial dimensions of the tile supplied.” Example: for tiles having a total variation of 1/16” in facial dimensions, a minimum of 3/16” grout joint shall be used.

In my experience as a tile contractor when using natural tile (which has a lot of variation}, the tile manufacturer will often recommend 1/4” grout joints or larger. Using this standard, many calibrated tiles I installed would require a 3/16” grout joint, and many rectified tiles would require an 1/8” grout joint.

Presenting this information as the industry standards and guidelines – and not as your personal opinion – can be beneficial in changing the owner’s perspective.

Running bond, brick joint, or any offset pattern

Considering the location of the offset joints in a brick pattern is an important part of layout and is also addressed in our standards. The TCNA Handbook states, “For running bond/brick joint and any offset patterns utilizing tiles where the side being offset is greater than 15”, the offset pattern will be a maximum of 33% unless otherwise specified by the tile manufacturer. If an offset greater than 33% is specified, specifier and owner must approve mock-up and lippage.”

Since larger tiles have more warpage, installing an offset joint at 50%, the high point of one tile will be next to the low point of the next tile, creating unacceptable amounts of lippage. 

The reason this offset is important is because larger tiles may have more warpage up to a cap designated in ANSI A137.1. When installing these tiles on an offset joint at 50%, we now have the high point of one tile (the middle) next to the low point (the ends) of the two adjacent tiles, which can give us unacceptable amounts of lippage.

System modularity

When laying out certain patterns, it is necessary to use tiles that are modular in nature. Modularity is defined per ANSI A137.1 as “Tiles of various nominal dimensions are sized so that they may be installed together in patterns with a common specified grout joint width.” Verifying system modularity and specifying the allowable grout joint for the pattern of an actual tile to be installed are the responsibility of the design professional. If the tiles are not modular or made for the pattern you will install, there may not be room to account for the grout joint.

If the tiles are not modular or made for the pattern you will install, there may not be room to account for the grout joint.
This diagram of a basketweave pattern illustrates that the tile dimensions must allow room for a grout joint in the measured pattern. 

An example of this is a basketweave pattern. If the tiles to be used were 4” x 8” exactly they would not account for the required grout joint. If the two short sides were exactly 4” and met the long side which is exactly 8”, they would butt tightly to each other. However, if the dimensions of the tile were 3-7/8” x 8” this would allow for a 1/4” grout joint and therefore be modular. That is a very simple example but this same principle would also apply to many patterns that include multiple sizes of tile.

Grid lines

Using a grid system is not the only way to do great layouts, but is a tremendous tool.

One skill set that it seems most every professional tile installer possessed in the past is the ability to lay out an entire floor using grid lines. With this method of layout, the entire area to receive tile is gridded out with chalk lines to show where every tile will be placed before the installation starts. The attached picture shows installation going in this way.

The advantage of this system vs. getting reference lines and using spacers is three-fold.

Using a grid system gives installers a great advantage on the job.
  1. You can quickly calculate the exact size of every cut in the installation before you start and can communicate that information to the owner or responsible party before you begin work.
  2. You can have multiple installers in different areas of a project all working simultaneously, and they will be able to tie into each other’s work.
  3. When tiling continuously around obstacles like an island or carpet inset, you can connect your work more easily.

Movement accommodation joints

Non-linear movement joints can be planned to not disrupt the flow of pattern in a layout. 

One of the leading reasons for tile installation failures is lack of movement accommodation joints. The response installers often give for not installing movement accommodation joints is that these joints create an aesthetic issue that their customer would never accept. There have been changes in ANSI A108.01 that now allow for nonlinear movement accommodation joints, which would not disrupt the flow of a pattern in a layout. Crack-isolation membranes can also be used in accordance to TCNA Handbook method F125. This allows the soft joints to be moved to the adjacent grout joints without disruption to the layout or tile pattern. With proper planning in coordination with the owner and design professional, a layout that looks great and has the appropriate movement accommodation joints is more possible than ever before.

We will discuss this information and much more in our upcoming NTCA Workshops. At our in-person events, we will have a variety of stations for hands-on layout training. In addition, keep an eye out for notices about our local NTCA Virtual Workshops, sponsored by a host in your area. These virtual workshops will be set for the dates of the original physical workshops that had to be temporarily put on hiatus. These will be given in webinar format, and will offer opportunities to type in questions about the material being presented.

To see a list of our virtual and in-person training events, go to the Education & Certification tab on the NTCA website.

Stay safe, and I will look forward to seeing you on the road soon.

A new hope: Louisville contractor transforms shop bathroom with Star Wars shower mosaic

Stanton’s Chinese manufacturing partners took great care in creating the Star Wars mosaics. Luke Skywalker’s lips used about 12 colors alone. 

A long time ago in a galaxy far, far away…..Jonathan Stanton was born, the same year that the blockbuster phenomenon Star Wars soared across the silver screen, and changed film history forever.

The year was 1977, and the galaxy was actually our very own Milky Way. Over the intervening years, the force awakened as Jonathan grew up learning the tile trade from his father. In 2002, he established Jonathan Stanton, Inc., in Louisville, Ky., specializing in stellar residential installations. 

Flash forward, and Jon and his wife have two sons, 14 and 10 years old, and a 4-year old daughter – and they all LOVE Star Wars. 

So, inspired by his children, he set out to transform the crumbling outdated bathroom in the shop he bought several months ago into a homage to the Star Wars legend, and an example of creative themed bathrooms that designers could attempt for their clients. “I wanted to take a fun approach and be the cool dad,” Stanton said. “I wanted to do something that wasn’t like anything else out there.”

It took Chinese artisans two weeks to create the mosaic of Yoda’s face. 

Stanton amassed his crew of three men to work on the 1,200-square-foot Jedi Unisex bathroom, on weekends, amounting to about two months of framing, electrical, plumbing, and all the tile work – which alone took two to three weeks.

Meantime, he was in touch with companies he’s developed partnerships with in China to create five mosaics of Darth Vader, Luke Skywalker, and Yoda for the shower, derived from online images of the characters. “It took almost three months to have the murals made on mesh sheets, and Yoda’s face alone took two weeks,” he said. “Hundreds of colors of glass were used. The lips of Luke Skywalker alone use about 12 different colors.” The company shipped the mosaics in pieces, designed to lock together, along with extra glass tiles for repairs or to fine tune the installation.

Stanton was careful to check into the licensing ramifications of his bathroom. Since it was for his own use, there was no infringement of using the likenesses of movie characters in his project. 

Installing the mosaics in the Star Wars shower.

His job also utilized Repel Systems XPS closed cell extruded polystyrene foam building panels – 1/2” board on the wall, 5’ x 3’ linear presloped shower pan with tileable drain cover, and solid foam curbs and shower header. Stanton wrapped exposed iron pipes and built shelves with 1.5” thick Repel panels. Stanton owns Repel Systems, with product manufactured to meticulous standards in China. Repel Systems recently joined NTCA as an affiliate member.

Positive partners

Stanton’s work with Chinese companies has been a positive, and the partnership he has cultivated with his Chinese partners has opened the door to not only new business opportunities but to outstanding work done to his exacting standards. “A lot of people think Chinese goods and craftsmanship are a negative connotation,” Stanton said. “I’ve had to peel back the layers and work through some of that…what you buy needs to be done with such care. Initially, mosaic orders were filled quickly but they weren’t what I wanted.” After some discussion and direction, his manufacturing partner met and exceeded his expectations. 

Similarly, Stanton and Repel Systems (repelsystems.com) Chinese manufacturing partner Xuancheng JIT New Materials Tech. Co., Ltd., spent 1-1/2 years before even launching the system. “I’ve asked for emissions reports so we are dealing with only the best of standards for the environment,” he said. “We tested it to make sure we have a top quality product.” The products have UPC certificates through IAPMO Research and Testing, and shear strength that surpasses the U.S. ANSI A 118.10 standard.

Foam building panels from Repel Systems formed the shower, shelves, curbs and other elements. 

Stanton has built strong connections and relationships with his partners and their families, and is in touch with them seven days a week. “I was sad to have to recently cancel a trip to China for a wedding due to the Coronavirus,” he said. And he is still dealing with an additional 25% tariffs on products imported from China. But despite that, the connection, quality, and cost of products he’s developed in partnership with Chinese companies is worth it. 

Walls and floors

In addition to the stunning mosaics, Stanton used Emil America Italian Tele Di Marmo Statuario Michelangelo Lappato Lucido porcelain 24” x 48” tiles for the bathroom walls, and 12” x 24” Emil America Tele Di Marmo Calacatta Renoir Lappato Lucido porcelain installed in a modern herringbone on the floor. The black and white palette reflected the Rebellion versus Dark Side theme throughout the films. 

Stanton’s crew poured almost a 1-1/2” of self leveler before snapping electric floor warming wires into the 3/8” Repel Heat Board. 

About 300 square feet of large-format, rust-look Emil Ergon Metal Style 12” x 24” Revival tile clads the outside of the bathroom envelope, transforming it into something you might find on Tatooine. Emil product was sourced from Patria Coverings Co., in Indianapolis. 

LATICRETE setting materials were used throughout, from TRI-LITE mortar for floors and walls, and MULTIMAX LITE mortar – rated for glass – for the murals. SPECTRALOCK epoxy translucent grout was a must for the murals, Stanton said, since the translucent material “takes up the inner tones of red and blues in the glass tiles, and helps blend in the color.” PERMACOLOR SELECT was Stanton’s choice for grouting porcelain floors and walls. 

To level the “out of whack” subfloor prior to installation, Stanton’s crew poured almost a 1-1/2” of self leveler before snapping electric floor warming wires into the 3/8” Repel Heat Board. 

Stanton created a custom light fixture in the shower with Repel board, with rounded corners and tiled with mosaic. It provides light and the shower head runs through the middle of it. 

Another challenge that presented itself was the toilet, sunk into the wall beneath piping. Stanton chose to strike back by working around the old cast iron pipes, designing shelving around the toilet that is integral to the design of the space. 

As of this writing, the project is nearly complete, waiting for door hardware on order from China that’s been delayed by the COVID-19 outbreak. 

As a finishing touch, the bathroom is accented with actual Disney Star Wars light sabers and Resistance and Empire helmets. 

This contractor’s vision, professional connections and dedication turned an outdated, tumbledown shop bathroom into a new hope, full of fun and delight for years to come. 

As a finishing touch, the bathroom is accented with actual Disney Star Wars light sabers and Resistance and Empire helmets. 

Why proper substrate preparation is critical for tile and stone installations

If you are an attendee of our NTCA online free webinars, this title may sound familiar. That’s because back in February, ARDEX Technical Manager Mark Pennine presented an NTCA Webinar on this subject. And since it so perfectly fits the planned topic for this month’s Technical section, we decided to excerpt parts of this talk to address the issue of substrate preparation. An initial talk on the subject was offered in September. Want to watch that webinar or review the material in this article? Visit the NTCA YouTube channel and peruse our archived presentations there: http://www.youtube.com/c/NationalTileContractorsAssociation. – Ed. 

Proper substrate preparation has long been an essential aspect to a successful tile or stone installation. But today’s tile trends of large-format and gauged porcelain tiles and panels (GPTP) make flawless substrates even more critical. 

Smaller tiles, like 6” x 6”, 8” x 8” or even 12” x 12” format, allow for conforming to inconsistencies in the substrates much easier. Massive GPTP products don’t offer room for variances in the substrate and need a flatter, smoother substrate. Tolerances for these products are tighter. For instance, substrate tolerance for tiles with all edges less than 15” in facial dimension is 1/4” in 10’ and 1/16” in 12”. But for large-format and gauged porcelain tiles and panels, the tolerance is inverse to the size – the larger the tile, the less the acceptable tolerance: 1/8” in 10’ and 1/16” in 24”is industry standard. Natural stone has always required more stringent surface flatness tolerances. Gauged porcelain panel recommendations are following those guidelines.

Installing large-format tiles is much more manageable and stress-free when self-leveling has been done ahead of time. Gauged porcelain panels installed on a properly-prepared substrate results in a beautiful clean installation, with a monolithic look. 

Plan for performance

There is no room for shortcuts when preparing a substrate. When the job is well planned, substrates are prepared to industry guidelines and the installation is performed by qualified labor, the result is beautiful long-lasting installation.

Closely evaluate floor before beginning installations and remember this phrase: “Prior proper planning prevents painfully poor production.” By following proper prep guidelines, you will maximize long-term performance while reducing installation costs. And you will minimize costly callbacks and enhance your reputation as a quality installer. 

The five keys to a successful installation are:

  • Attend training. Be educated. 
  • Substrate preparation – it’s always at the top of the list
  • Using the right tools
  • Use your resources
  • Use Trowel & Error (bitly.com/trowelanderror)

Preparing the substrate: weak or soft top layers

ANSI A 108.01 general requirements mandate that substrates must be:

  • Clean, structurally sound and solidly bonded
  • Free of bond-breakers (sealers, curing agents and form release)
  • Flat and smooth
  • Free of excess movement

Soft or weak top layers pose problems in structural integrity and bonding and must be removed to achieve a strong, lasting bond. The most effective way to remove a weak top layer or contamination from concrete is by mechanical means. When mechanically preparing a substrate, be sure to use proper tools and protective equipment and prepare joints in wood subfloors prior to the installation of self-leveling materials. 

Bond breakers

For concrete substrates, always mechanically remove:

  • Release agents (tilt up construction)
  • Paint
  • Drywall mud
  • Sweeping compounds
  • Oil/grease
  • Asphalt/tar

For wet or moist cured (burnished) concrete where no curing compounds have been used, and superficial contaminants have been removed, you can use the appropriate primer to prepare the substrate. 

When you are dealing with sealing compounds on concrete, you must be able to determine what type of sealer was used and how to proceed before priming. 

  • Acrylic or epoxy compounds – remove superficial contaminants 
  • Urethane compounds – remove down to clean, absorbent concrete 
  • Acrylic non-dissipating curing compounds MUST be defined as “ACRYLIC”. There’s no mechanical prep necessary – just remove superficial contaminants and prime as necessary. 

You can only remove adhesive residues on concrete. The adhesive must be scraped down to a well-bonded thin layer or residue. But if the adhesive is water soluble, it must be COMPLETELY mechanically removed before proceeding. Don’t use adhesive removers or solvents, since these will then become bond breakers. If your substrate is plywood, you can’t remove adhesive residue and then install on that plywood. You must remove the plywood with the residue and or apply a new layer of plywood over it before installation. 

Sweeping compounds you may encounter at construction sites commonly use wax or are petroleum based. They can leave a bond-breaking residue on the concrete surface, and must be removed. 

Tilt up wall construction utilizes parting/release agents to prevent concrete wall from sticking to concrete slab, and act as bond breakers. They must be mechanically removed before proceeding. 

If there is material on the concrete that will affect the bond and you can’t identify it, err on the side of caution and mechanically remove it. 


Priming is a critical step before self leveling since primers prevent porous substrates from drawing moisture out of the product, enhance bonding and extend working times of self leveling products. They are also bonding agents and will help setting materials bond to certain non-porous surfaces they would otherwise struggle to bond to on their own. Primers will usually be single-component acrylic or epoxy. Check with manufacturers for proper primer for your material, and the installation procedures. 

Self-leveling underlayments

Don’t make the mistake of thinking that self leveling products are structural repair products – they’re not. They are surface repair products that prepare the substrate for the installation of finish flooring. But the substrate itself must be structurally sound. If structural repairs are needed, be sure to consult a engineer. 

FLAT AND SMOOTH: In most cases, flat and smooth is what is required, but level is not always needed. If level IS required, be sure floor is plotted and leveling pins are installed, then pour sufficient material to achieve level.

Self leveling is ideal for flattening and smoothing large areas. Some floors may require only 1/8” – 1/4” Others may require 1/2” up to 1-1/2”. Always use the proper product for the application. 

SLUs for tile and stone installations can help save time and money by speeding up installation and minimizing effort and repairs due to undulating and uneven surfaces. Most SLUs can be walked on as soon as three to four hours, allowing installers to start their layouts. Troweling can usually occur in six hours. 

SLU OR TROWEL GRADE PATCH: Sometimes a trowel grade patch is all that’s needed. Other times, patching will take place before self leveling to fix cracks or spalls in the concrete. 

Figure out if you need 1/8” or less to remedy the out-of-lane substrate. If it’s less than 1/8”, use a trowel grade on smaller jobs, and for larger jobs, use a high-flow SLU or patch. If your substrate is more than 1/8” out of grade, use a SLU. SLUs have exceptionally high flow and will heal even when installed at thin applications. 

Do you need a slope? If the slope is greater than 2%, use a trowel grade material, and use a self-leveler if less than a 2% slope is needed. 

Know your self leveler! They are not all the same. Some may be limited to certain types of substrates, or limited in thickness or take longer to dry. Use the product recommended for your application. Consult the technical person of the manufacturer of your choice. And since SLUs are very flowable, be sure to close off all openings before you begin pouring. 

TOOLS: Some essential tools make self leveling easier and more efficient. Two popular tools designed to place and break the surface tension when using self levelers are:

  • The spreader – the cleats on bottom allow for adjustments to determine how much material is applied to the floor.
  • The spike roller breaks the surface tension. 

RADIANT HEATING: Self levelers are the best way to encapsulate floor heating wires. Once the SLU has cured, the installer can work on the floor without worrying about damaging the heating wires. And gypsum based SLU is ideal for use over in-floor hydronic heat tubing. 

UNDULATED FLOORS – An undulated floor covered with cement board is still an undulated floor. A SLU offers a bondable surface and a flat and smooth finish. 

Installing over existing tile installations

Installing over existing tile installation is becoming more popular since it eliminates costly tear-outs and health risks from the resulting dust. Be sure to investigate primers that are designed for non porous surfaces if you are tiling over tile, and make sure existing tile and stone – which will become your substrate – is well bonded. Another step you may need to take is to strip all wax and allow surface to dry thoroughly. Be sure to consult the manufacturer to determine suitable substrates and best product recommendations, and prime as necessary with a product designed for the porosity of your substrate. 

SLUs have come a long way

The first self leveler was introduced to the market in 1978. Today, there are a range of application devices and pumps that use up-to-date technology and provide easier workability. 

For small jobs, you can use manual barrel mixing. It’s very important to measure water capacity and to use proper tools to be sure right amount of water is added every time. 

Additional tools and resources help the job run smoothly, such as a cart for the mixing barrel, a spiked roller to break surface tension, dust control system and leveling pegs. 

For larger jobs, new technologies range from portable small capacity pumps to medium capacity pumps that are modular or trailer mounted, and high capacity pumps perfect for urban applications. Evaluate your needs to choose the appropriate pump for your needs. 

What could go wrong?

SLUs may seem miraculous – but they are not foolproof, and in some instances, they are just not an option. For instance, you’ll run into trouble with a self-leveling compound installed over thick layer of weak adhesive, since that will result in a cracked unbonded self leveler. 

Overwatering leads to weak top layer and noticeable discoloration. 

Disbonding can occur as a result of poor substrate prep and pouring over a contaminated substrate can lead to failures.

Final considerations

  • Substrate prep is key to all tile and stone installation success
  • There’s always a “right way” solution
  • Stay in tune with industry trends and best practices
  • Be aware of the inherent challenges
  • Use your resources – industry guidelines, manufacturer technical services, supply partners, etc. 

Mortar, mortero or mud: why you need to know how to work with this ancient material

The use of mortar in construction has been around since around 6500 B.C., and still has a place in today’s construction projects.

Martin Brookes, Heritage Marble & Tile, Inc., giving a talk on best practices at Coverings.

The ability to fix and shape substrates makes it a perfect material to fine tune and flatten to achieve a perfect setting surface for tile. The skill is an art form, but in today’s tile craft, its importance has dimmed in light of other quicker, more cost-effective systems. These new technologies do have a place, but will never take the place of a mortar bed in some applications.

Contractors around the country may approach the use of mud differently, but the outcome is the same: a true, plumb, flat surface.

At Heritage Marble & Tile, Inc., in Mill Valley, Calif., we have just completed a complicated installation of glass mosaic and handcrafted tile that could not be accomplished without the use of mortar beds. Recently, our mortar beds have been restricted to floor surfaces, but occasionally we are asked to do a complicated installation that requires the use of mortar beds on a vertical surface. We have a very talented workforce who are skilled in doing mortar beds; this has separated us from the pack. I would highly recommend that you keep the skill alive through training your installers, because you never know when you might need to use it.

When I scroll through Facebook groups, I see a lot of discussion around mortar beds, with some  installers never having created a mortar bed and others doing it on a regular basis. 

At Heritage Marble & Tile, we create mortar beds on an as-needed basis. We like to take a system approach in many cases, but the fact that we can do it when needed opens the marketplace for more artisan projects.

Mike DeGuisti, president of NTCA Five-Star Contractor Terra-Mar in Oklahoma City, said, “Mud work is becoming a lost art, at least in my part of the country. I remember coming up in the trades when floors were all floated, either direct-bond or with a cleavage membrane and walls and ceilings were all lath and plaster. Floating of floors – especially in areas with drains – is the only way to achieve the proper slopes. Floating of the walls allowed us to have perfect tile layouts without all the squirrely cuts to fix the walls we receive in today’s construction practices.”

The Grotto is a complicated project involving glass mosaic and handcrafted tile that Heritage Marble & Tile, Inc., just completed. It could have not have been accomplished without the use of mortar beds.

LATICRETE Mud Event Circa 2015

Around 2015, LATICRETE held a mortar workshop in Corona, Calif., for the Tile Geeks Facebook group members from all around the country to either mentor or learn how to do mud. “It was a well- attended event with installers who had never done mud work now implementing it in their workplace on a regular basis,” DeGiusti said.

One of the attendees was Robert Davis, owner of Davis Solutions from the Pacific Northwest, who’s been in the trade for 13 years.

“When I began as a helper, every shower we built was a B-415 (although I did not know it at the time),” he said. “I chopped a lot of deck mud in a tub that has since been passed down to me by Jeremy VonRuden. For a while, I had no notion that wall mud even existed.”

At the event, Davis got some helpful hands-on training from Jack Hamilton, Shaun Haley, and “a lot of other lifelong mudders,” he said. “I got a taste for mud work, and have been dabbling in it since. I still float almost every shower pan, and technology has speeded up the process. Now I use a Bucket Mortar Mixer, and my kids use the old mud tub as a sled in the winter. Topical waterproofing advancements have also shaved install time.

“I have successfully floated interior walls for thin glass mosaic, which would have been a much more daunting task without tremendous support from the MUD Facebook group,” he explained.  “They held my hand (digitally) through the process, and a few repetitions have boosted my confidence. Mud is an ability that I need in my repertoire, and I’ll continue to sharpen it.”

 Davis is staunchly pro-mud. “Our trade needs mud,” he said. “The awareness of mud work is more so today than ever – and so is the recognition that the art needs to be learned. Anyone interested in learning to float should consider traveling to Fresno, Calif., for an annual MUD event, where veteran and aspiring mudders alike meet to sling mud in a fun and educational environment. More information is available at themudevent.com.”

In 2015, members of the Tile Geeks Facebook group from across the country descended on a mud class in Corona, Calif., that LATICRETE offered, to either mentor or learn how to do mud. 

Flexibility, creativity and perfection

John Cox of NTCA Five-Star Contractor Cox Tile in San Antonio, Texas, is a long-time mud proponent, who has used the one-coat method of applying mud in his business for 45 years. 

“We use mud as an advantage in bidding work where demanding and costly materials are used in some of the homes we work on,” he said. “A flat, level and plumb surface is critical in these installations. Sometimes we have to build arches on shower jambs and the only way to achieve this is with mud. It is paramount to educate the customer as to why.”

Cox said he is seeing more interest in learning the art of mud work. “Tile men and women are aggressively seeking the training and knowledge in understanding the importance and benefits of mud work,” he said. “We have built Jacuzzi tubs with mud that simply cannot be built with any other product. You have so much more flexibility in building the walls flat and level, instead of using the newer technology and spending the time rendering walls to make them flat and level. Unfortunately with the lack of skill in some framers – and green lumber – you have all kinds of walls that are either warped, humped or out of level.”

When seeking absolute perfection in the installation, mud is the material of choice. “Small penny rounds and other smaller tiles are challenges since they show every imperfection in the substrate, such as round corners,” Cox said. “We do all of our showers, tubs and floors with mud. We recently had a customer request some of the newer technology of products. But after explaining the benefits of ‘old school mud’ he agreed to go with our method. There may be substitutions but there is no equal.”

“Tile men and women are aggressively seeking the training and knowledge in understanding the importance and benefits of mud work,” said John Cox, of NTCA Five-Star Contractor Cox Tile in San Antonio.

For flat floors, use mud

Cox emphasized that mud is the only way to achieve a perfectly flat floor, especially when working with large concrete on-grade floors. Building a mud floor allows you to create a flat substrate to meet ANSI standards of floor flatness. 

It especially comes into play in creating level transitions from different elevations, or substrates with different finished heights, he said. “This is achieved by starting with the correct depth off the floor and floating the floor off of that point,” he explained. “Mud on floors allows you to float to a drain or multiple drains or on a balcony to create the proper drain of 1/4” per foot to the edge.”

It’s also important to build in movement accommodation when working with mud. “One thing to satisfy EJ 171 is we install 1/4” foam around the perimeter so the mud is not coming in contact with the wood plates on floors,” Cox added. “Most think EJ 171 pertains to only the tile and grout. Tenting can occur when moisture comes in contact with the plates if this is not protected and

Mud may be more affordable in the long run, as well. “I always tell my builders to err deeper instead of shallower for floors or walls,” Cox said. “An extra layer or coat of mud is far cheaper than reframing a wall or chipping concrete on a floor.” 

Navigating the limitations of mud

Mud may be miraculous, but the knowledge of methods is crucial in executing mortar beds. That’s why the TCNA Handbook for Ceramic, Glass and Stone Tile Installation should be studied and understood beforehand for walls and floor methods.

As versatile as mud work is, the limitations of the mortar beds are not always fully understood. One needs to follow the guidelines to create a plumb, true substrate preparation to avoid any complications that may arise from the improper application of the methods.

Heating up the house

Manufacturers offer advice for successful floor warming installations

Electric underfloor heating systems have come a long way since the old days. They offer comfort underfoot, ease of installation, and smart controls that can be programmed or can learn a consumer’s pattern of use, delivering toasty warm floors when users arrive home.

An example of today’s electric floor warming options: ARDEX FLEXBONE® HEAT In-Floor Heating Systems

And fortunately, ceramic and porcelain tile are excellent choices for radiant heated flooring, said Thomas Utley, Technical Specialist FLEXBONE HEAT/ARDEX Tile and Stone Installation Systems. “They have high thermal conductivity and retain heat better than other flooring choices. The thickness of the tile has little impact on the heat output but the heating time is increased with thicker tiles.”

But like any product, there are things to keep in mind for a successful electric floor warming installation. We surveyed a few of the top electric floor warming manufacturers to get their recommendations for foolproof installations.

Top tips for contractors

What are the top things contractors should keep in mind when working with electric floor warming systems? First of all, “Contractors should be mindful that the desired flooring finish must be compatible and tolerant of the thermal fluctuations these systems can exert, in order to ensure there is no damage to the flooring,” LATICRETE’s International’s Art Mintie, Senior Director of Technical Services, said. 

The Warmly Yours system uses the low-profile Prodeso Heat mat with 3.7 watt electric TempZone heating cables, ensuring proper spacing throughout the project. 

He also cautioned contractors to choose the best type of underfloor heating system that suits their specific needs. “Hydronic (liquid) systems are a popular alternative that rival electric radiant floor heating systems by pumping heated water from a boiler through tubing laid in a pattern under the floor,” he explained. “These systems are also often more expensive and are recommended to be installed at the time of construction, whereas electric radiant floor heating systems are a great retrofitting project that can be done at any time.”

Since these ARE electric systems, Regis Verliefde, Territory Director, NAM of Warmup said, “It’s important for the tile installer to double/triple check coverage and spacing to provide the desired solution for the consumer. While most systems install in a similar way, some are for comfort heat and some are built to heat the whole room. Installers should get familiar with which systems do what and what spacing or insulation to provide on a cold basement slab, for example.” 

Respect Ohm’s Law

The Warmup Alligator tester clips straight to the heating cables and monitors them during installation. 

It’s a good idea to recognize that cutting electric heating elements to make it fit your project is a bad idea, said Julia Billen, owner and president of Warmly Yours. “Because of Ohm’s Law, if floor heating cables are shortened, the resistance of the cables will be correspondingly lowered, which in turn drives up the voltage and wattage,” she said. “This can cause the heat output of the system to go over the limits set by national or local code or, in some cases, even cause the heating system to fail. It’s important to work with a floor heating distributor to ensure you have the right amount of heating elements for your project.”

She also recommends testing the heating elements often with a digital ohmmeter – before, during and after installation. “In between ohmmeter tests, we recommend that you use a continuity alarm that is connected to the heating cables that will sound an alarm if the cable is damaged,” she added. She also advised taking measures to avoid damaging the floor heating cables during installation. 

“One way to avoid this is to install the floor heating mats (if that’s the system-type being used) upside down so that the mat material can protect the cables from damage by trowels or other tools,” she recommended. “Another way is to avoid using metal trowels or floats to apply the thinset on top of the heating system, as these can occasionally damage the floor heating cables.”  

Plan ahead

Carefully calculate the length of heating cable required based on the floor space, minimum clearance from fixed building elements and other objects.

Sean Gerolimatos, Director of Research and Development with Schluter Systems, emphasized preplanning before you start. “It is important to read and understand all product/system and code requirements, create a detailed plan, and execute it diligently,” he said. 

Gerolimatos also suggested, “Carefully calculate the length of heating cable required based on the floor space, minimum clearance from fixed building elements and other objects, and coverage of the heating cable at the manufacturer recommended spacing.” Another great suggestion he offered was to be sure “the owner and any other trades on the project know where heating cable is installed (photos are helpful) to avoid damage during subsequent work.”

Be sure to order the proper amount of heating wire for the job. Shown is the Prodeso Heat system by Progress Profiles.

Domenico Borelli, Vice President and CEO of Progress Profiles America echoed other suggestions, adding that it’s crucial that the “subfloor is suitable for tile installation and electrical radiant heat.” One may think that goes without saying, but establishing a suitable subfloor is essential in any tile installation, especially one that uses electrical mats and cables to provide floor warming. He also emphasized exact, accurate measurements and ordering the proper amount of heating wire for the job. 

ARDEX’s Utley also advised contractors to “Plan to include a second sensor wire in your layout. Only one will get connected initially. The back-up sensor can then easily be connected to the thermostat in the wall without disturbing the flooring installation.”

Even heat distribution is a must

Underfloor heating can develop cold spots when the warmth cannot be evenly distributed. LATICRETE’s STRATA_HEAT™Thermal Pack – used  in conjunction with the STRATA_HEAT electric radiant floor heating system – employs Thermal Diffusion Technology™ to distribute heat uniformly throughout the adhesive. 

In addition, heat sink and heat loss are two primary issues that can arise when installing electric radiant floor heating, LATICRETE’s Mintie offered. “Generally, a backer board with insulation properties can be placed over the concrete slab in order to assist and prevent these from happening. For plywood substrates, installers should conform to TCNA Handbook for Ceramic, Glass and Stone Tile Installation requirements when installing ceramic, porcelain or dimension stone tile finishes over heated flooring systems.

The new Mapeheat system from MAPEI includes membrane, cable, and three kinds of thermostats to choose from. 

Sonya Moste, Product Manager, MAPEI Crack Isolation and Sound Control Membranes also advised contractors to plan for even distribution of heat. “Hot spots and cold spots detract from the experience of a heated floor so consistent watt density is critical,” she said. “Things that make this task easier are pre-built custom mats designed specifically for the individual floor shape or a floor heating membrane with heating cable that has flexible layout requirements (i.e. no restrictions on run length and no requirement for tension loops).” She also suggested “future-proofing the installation with WiFi thermostats featuring connectivity with multiple connected home systems (such as Google Assistant, Amazon Alexa, IFTTT, Nest, Control4, etc.) and also offering an Open API for custom smart home integrations.” 

Don’t underestimate manufacturer support, she advised. “Choose manufacturers that will back their products and the completed installation for 25 years, or more, and make sure the warranty is not pro-rated (in other words, make sure the coverage isn’t for half the value after half of the warranty period has passed),” she said. And a knowledgeable technical support team that offers on-site and telephone consultation is worth its weight in gold.

Working with electricians

To follow code, you will need to work with an electrician to complete this project. It’s essential to coordinate your services for ultimate success. Progress Profiles’ Borelli said, “A 10 minute conversation at the job site will save time and money and aggravation later.” And MAPEI’s Moste pointed out that it’s a good idea to “work with manufacturers that have experience dealing with both trades. The best certification programs will cater to tile contractors and electricians.”

Tile contractors and electricians should test the heating cables at every stage of the installation.

A good suggestion from Warmup’s Verliefde is to leave the product tag with wattage and voltage attached to the lead wire or inside the roughed-in electrical box, ensuring the right voltage breaker is provided for the job. He also recommended that contractors locate where the electrician has roughed-in the thermostat box and start the system at the base of that point on the wall. “And if your system is over 250 sq. ft., have a quick chat with the electrical contractor to discuss power supply and the best location for the power connections,” he added. 

Warmly Yours’ Billen insisted that tile contractors and electricians test the heating cables at every stage of the installation, and record and communicate those readings to each other to ensure the system remains functional at every stage of the process. 

At Schluter, Gerolimatos noted that different floor systems may have different orders of installation, so as he suggested earlier in this story – plan and acquaint yourself with the quirks of the particular system you are working with. 

“It’s also important to establish where the responsibility of each trade begins and ends,” he said. “For example, some jurisdictions allow tile setters to layout the heating cables, where others require the electrician do so.” 

And finally he mentioned that connecting a 120V heating cable to a 240V power source is one of the most common mistakes when installing electric floor warming systems. “This can be easily avoided with a little bit of planning ahead of time,” he explained. “Check the available power source and make sure to order the corresponding heating cable (120V cable for 120V power, 240V cable for 240V power).” 

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