TILE Magazine recently had the opportunity to discuss the topic of “Surface Preparation” with a handful of established installers within the tile industry. In order to get some of their opinions on the broad topic, the installers were asked a series of questions that addressed issues such as common problems faced when preparing a surface for a tile installation and materials that are utilized. Panelists in the session included:
  • Dan Welch, Chairman of the Board for the National Tile Contractors Association (NTCA); Owner, Welch Tile & Marble, Kent City, MI
  • James Woelfel, President and Technical Committee Chairmen of NTCA; Vice President and Estimator, Artcraft Granite, Marble & Tile, Mesa, AZ
  • Nyle Wadford, Board Advisor of NTCA; Technical Committee Vice Chairman of NTCA; Tile Council of North America (TNCA) Handbook Committee Member; ANSI ASC A108 Committee Vice Chairman; President, Neuse Tile Service, Inc., Youngsville, NC
  • Christopher Walker, Chairman of ANSI A-108 committee; Chairman of US TAG ISO TC-189; Chairman of NTCA Methods & Standards; Board of Directors for Associated Builders and Contractors of Virginia (ABC); 2nd Vice President of Board of Directors for NTCA; Voting Member for NTCA Technical Committee; Voting Member for TCNA Handbook Committee; Vice President of Northeast Region, David Allen Co., Inc., Raleigh, NC

In your opinion, what is the number one problem to an improperly prepared substrate?

Welch: Bond failure, drastically reducing the life cycle of the install.

Woelfel: Two things — one, putting tile on a substrate that’s not flat enough to put it on, especially as the tile gets longer and more elongated. Two, you have a bond breaker situation where the concrete has been over troweled too hard where it won’t accept anything or the concrete finisher puts a curing compound on it where you can’t bond to it with a mortar. Those are the two biggest things we run into.

Waker: As specified tile modules continue to grow larger, longer and in some cases thinner, the installation specialist cannot afford to be unaware of the importance and highly specialized requirements of a properly prepared installation surface. 

Not only is the surface critical to the longevity of the installation, your preparation of it will be highly scrutinized in the event of any failure of the more and more demanding technical requirements of specialty ceramic, porcelain and glass products. This conversation is as important for walls as it is for floors. Proper use of preparation materials may be the difference between the success or demise of your company.

Preparation of any substrate should not be given away as a value added service provided at no charge by your company. You have not only an obligation to educate the owner or end user as to the deficiencies of the substrate, but also the various options available to correct them and the consequences of any choices made which may compromise the suitability of the substrate.

View this as a profit opportunity to correct what are design deltas between the substrates, specification inconsistencies and manufacturers conservative recommendations. Remember, in almost all cases, once you begin your installation, you have accepted the existing condition.

Wadford: An improperly prepared substrate leads to an improper tile installation. Preparing your substrate properly prior to the installation of your tile avoids the possibility of the completed installation not meeting established installation standards regarding lippage, coverage, bonding, vapor transmission, etc. A properly prepared substrate in any tile installation is vital to the success of that installation.

Have you taken any training or certification courses on surface preparation to better educate yourself?

Woelfel: No, it’s called experience. My employees have. One of my guys is ACT-certified on Large-Format Substrate Preparation. I was chairman of that committee that developed that test.

Welch: I have. CTI, ACT Mud Wall, Mud Floor, Large-Format Tile, Shower and Waterproofing.

Wadford: Yes, I am frequently attending seminars, symposiums and manufacturer training sessions regarding proper use of setting materials and surface preparation products. These include, but are not limited to, programs presented by the National Tile Contractors Association (NTCA), events like Total Solutions Plus, Coverings and Surfaces, and direct training from the manufacturers themselves. These products are constantly changing and to be up-to-date on the most current products and the amazing things you can accomplish with them, you must be in a state of perpetual continuing education to be knowledgeable.

Walker: Since the manufacturer’s recommendations supersede the ANSI and Tile Council of North America’s (TCNA) recommendations, your first point of reference, training and direction should always be the manufacturers themselves. Much training is provided free or at least supplemented by the manufacturers of specialty and allied products. Take advantage of these many opportunities as well as industry trade shows or trade organizations’ forums and seminars in your area. Our company constantly looks to our manufacturing partners for this training.

Does surface preparation differ for large-format tiles opposed to smaller-sized ceramic or porcelain tiles? Why or why not?

Welch: No. Surface prep is similar on all tile. The main difference is what will hide and what will not. Large tile requires flatter floors and better attention to detail.

Woelfel: Yes, absolutely. It has to be flatter. General specs and standards for our industry are 1/4 inch and 10 feet. Then when you get to larger tiles, anything over 15 inches, it goes to 1/8 inch and 10 feet. As everything gets bigger, we need to concrete even better. I’m not talking level. There’s a difference between level and flat. I need flat as long as it works; level is too expensive, usually.

Wadford: Yes, and sometimes greatly. Large-format tiles, ones that are greater than 15 inches on any one side require much flatter floors than those floors and walls utilizing smaller format tiles. The larger tiles do not conform to the inconsistencies of the substrate like the smaller ones do and, therefore, require tolerances that are often twice as stringent. The surface preparation that is required to achieve this is often extensive and more costly than what is customary for small format tiles.

Walker: As mentioned earlier, the technical requirements of some specialty materials have such stringent needs in terms of movement and coverage that you limit significantly your chances of success if you are not following the manufacturer’s installation requirements. Any tile with an edge larger than 15 inches requires a substrate that is level (flat) within 1/8 inch in 10 feet versus 1/4 inch in 10 feet for smaller material. The larger the tile, or unusual the manufacturers requirements, the more important you seek out proper installation or preparation material.

Do you have to apply different types of mortars or adhesives (non-modified thinset, latex modified thinset, medium bed, 100% solids epoxy) for different types of tile (large-format, porcelain, ceramic, glass and stone)?

Wadford: Absolutely. Our industry’s setting material manufacturers have done a terrific job of providing installers products adapted especially for the installation of various types of tiles. Education on the design and capabilities of these products is key to providing professional quality installations and improved efficiency while doing so.

Welch: Yes. They are all good products for differing methods, products and expectations.

Walker: There are many different recommended installation mortars and grouts for today’s specialty installations. Personal preference is often not the determining factor in what should be used for any particular material. Even though years of installation experience may guide you to properly using even the newest version of favored materials, take a moment to read the bags. If there is anything there that seems unfamiliar to you, join the club. All of us (installation professionals) have to be diligent to keep up with the continually changing, improving and developing technologies.

Woelfel: Absolutely. Non-modified usually falls in certain parameters of certain manufacturers. Then, you have large-format mortars (used to be called medium bed). Then, with moisture sensitive stone, you have to use an epoxy. It also depends on the installation. If you’re doing dairy or a brewery where there’s heavy chemicals, you have to do 100% solids epoxy to hold up against the chemicals.

If a surface is not properly prepared and flat, what are some of the problems that can occur?

Woelfel: Lippage — it becomes a trip hazard. When you have a bond breaker, the tile doesn’t stick — it pops loose. Those are the two biggest problems.

Walker: If the substrate is not sufficiently flat, you run the risk of unsupported voids under the material and edges. Point load considerations for thinner materials could be problematic. Voids of any size in freeze thaw conditions are predictably a failure in progress. If you are choosing to fill those voids with thin set, you are not only costing yourselves a fortune in under-estimated project costs, [but] you are also likely using the material in a way that the manufacture did not intend and may not warranty.

Welch: First, an improperly prepared surface will cause bond failure. Second, an improperly prepared surface will produce less than desirable expectations. Both will cost you money and both will decrease the business you can expect in the future.

Wadford: Lippage, mortar coverage inconsistency, loss of bond, damaging vapor transmission, shadowing, etc.

What two different types of products can you use to fix a floor?

Welch: All floors are not equal and all fixes require thought. Mortar beds, self-leveling underlayment materials (SLU), thin set, patching mortars, epoxy, grinding, priming, additives, and combinations of all.

Woelfel: SLU, and then we also use what we call deck-mud (that’s what it’s known as in the Southwest — sand and cement — used to level floors). We use SLU more than anything else — deck mud is used in unique circumstances, when a floor is really bad, or when a floor is a couple of inches lower than the other side. Most of the time, we’re using SLU.

Wadford: There are many, but we mainly use patching compounds and self-leveling underlayments (SLUs).

Walker: For about 3,000 years, thick-bed, packed sand — or similar packed leveling under-beds — have been under stones and decorative floors. Some of these installations survive today with little remedial requirements. That kind of track record need not be defended as the most reliable preparation for flooring. Unfortunately, our current construction methodology is relying on technology rather than craftsmanship. The installation materials are being replaced by multiple varieties of highly engineered mortars and fillers. Dry set - thinset installation mortars are the common methodology and like it or not, that will not change in the near future.

What is the proper way to mix and distribute self-leveling underlayment (SLU) materials?

Wadford: The proper way is to follow the manufacturer of the self-leveling underlayment’s instructions. Each is slightly different, so if you want a successful finished installation with no “issues” you are wise to follow the instructions they clearly make available to you on every bag and in their product literature.

Woelfel: Per the manufacturer’s directions because every manufacturer has a twist. Each one may work different, depending on the manufacturer. Above anything, you have to read their directions.

Walker: Even experienced installers need to be careful in the application of flowable mortars and self-leveling materials. In all cases, strict adherence to the manufacturer’s instructions. Practice and (error) is the most effective teacher in all cases to become skilled in the application of any materials.

Welch: It depends on the size area, thickness and complexity. Typical installs can use mixing pumps or a barrel type.

When using SLU materials, do you prefer slow setting or rapid setting?

Woelfel: Again, it depends on the situation. I like to use something slower if I have the time because it means I don’t have to work as quick and that cuts down opportunities for mistakes. Then, sometimes because of time constraints, I have to use rapid setting in order to get the job done in time.

Welch: Standard set unless the project requires fast. Fast will require more preparation and a more competent installer.

Wadford: That almost always is dependent on the parameters of the job in which the tile is being installed. If it is a quick turnaround job like a restaurant repair or mall installation, you will probably choose a rapid setting SLU. If you are dealing with areas where you will have to “work” the materials to achieve feathering to adjoining spaces, you will most likely choose an SLU with a longer open time. The time you are allowed to complete your installation is often a determining factor here.

Walker: In almost any application, we prefer the rapid curing versions of flowable mortar materials. Properly mixed and applied, there is little added difficulty in using these materials. Cost is the principle variable in determining which material to use.

Are all brands of trowel-applied floor patch SLU materials safe to use in preparation for ceramic and stone tile installations, or are there certain brands that are only applicable for tile?

Walker: In all cases, the manufacturers’ recommendations are the ultimate arbiter in determining which materials should be used in all applications.

Welch: No; all materials must be well thought out, and the project condition will require specific products for specific results.

Wadford: I am not aware of any that are tile- or stone-specific. Most of the ones that we use can be used for either. There are some backings on stone tiles (mesh, epoxy coatings, etc.) as well as some stones themselves that are very water sensitive, so the best course of action is to read the literature and instructions for the product’s limitations. If there are still questions, contact the manufacturer of the product and get their recommendation in writing. As always, educating yourself and not being afraid to ask for technical assistance from industry partners is the best course of action.

Woelfel: You need to pay attention to your particular installation and what product will work best in that installation.