Substrates for Ceramic Tile: It Pays to be Prepared

The Terminator 2000 from Innovatech is used to remove the existing ceramic tile and other floorcovering materials in renovation projects.

From the time you are a young child you are taught how important it is to be prepared. It applies to everything in life. Remember when you were young and had to take a test that you just didn't take the time to study for? It was like looking at hieroglyphics at times. Not a good feeling, to say the least. The fact is that most of us will fail in virtually all situations if we are not properly prepared for them.

A beautiful tile installation is not immune to this principle. Unfortunately, often a tile contractor cannot control all the elements of the project, and inherits situations that put the job at serious risk. Many of the problems a tile contractor encounters on the job have to do with the condition of the substrate that is to receive the tile.

The substrate is the area that will be directly bonded to with the ceramic tile. Depending upon the building practices of certain regions, it can consist of a variety of product types; including concrete, plywood, and others. First and foremost in your preparation is to determine whether or not the substrate is suitable for ceramic tile. This sounds simple but can be downright tricky.

The Predator 2400 Grinder from Innovatech is used primarily residential and light commercial construction for grinding, polishing, scraping or scarifying a concrete substrate.
The obvious issues that a contractor can address relatively easily relates to the materials that are specified on the project. This holds true in new construction or renovation specifications. At times a tile contractor can take a leadership role and assist his customer in material selection. Common substrates used in construction that are generally considered unsuitable for direct adherence for ceramic tile include particle board, hardwood flooring, foam board, oriented strand board (OSB) and scribing felt. Other products like gypsum underlayments, existing ceramic tile or terrazzo, natural stone and others may perform adequately with the proper installation materials and methods. When considering applying ceramic tile to substrates of a questionable nature, it is highly recommended to receive detailed installation instructions and product warranties for the products you submit.

Projects can even become problematic when you are dealing with commonly accepted substrates for ceramic tile. Concrete is a great example of this. Many factors exist at times that make a concrete slab unsuitable for tile installation unless certain steps are taken. Bond-inhibiting materials such as curing compounds, grease and oil and other potential contaminants are often present and must be removed prior to installing the ceramic tile.

According to many of our members, it is becoming increasingly common to find concrete slabs that have a variety of problems due to inadequate quality by the concrete finisher. Slabs that do not conform to both the concrete and the tile industry standards for flatness and levelness are among the problems cited by NTCA contractors. One of my members pointed out a frustrating common occurrence with one of his builders recently. "The slabs on almost all of these homes are smooth as a baby's bottom. It is like I am supposed to tile on glass concrete." This can be extremely difficult to bond to, as can the other extreme, caused by overtroweling, creating a weak watery cement slurry forming at the top of the slab.

Every year, the National Tile Contractors Association holds a technical and educational conference for the industry. This year, substrate preparation takes the stage as Tim Connelly, Business Development Manager for Custom Building Products, and Art Mintie, Director of Technical Services for Laticrete International, are collaborating together to address many of the most important issues in relation to properly preparing substrates and addressing common "real world" situations often encountered by the contractor on the jobsite. The program takes place September 14th-16th at the Hilton Las Vegas Hotel and Casino.

Joining Connelly and Mintie is Virgil Viscuso, Senior Sales Manager for Innovatech Products and Equipment, manufacturers of equipment used for mechanically grinding, scarifying, polishing, shot and bead blasting, and scraping and removing coatings, thinset, sealers and additives. Innovatech makes products geared towards both residential and commercial substrate preparation. The three will demonstrate some of the equipment commonly used on jobsites around the country.

The industry standard for variation in the substrate that is plumb and level should not exceed 1/4" in 10 feet, maximum. Often times this is just not the case, and the tile contractor must consider the utilization of leveling products, patches or applying a mortar screed to make the substrate suitable for tile.

Consideration for expansion joints must also be noted here, which can be obtained from the TCA Handbook in section EJ 171. It has been our experience that expansion joint placement and use has improved in commercial applications, but at times it continues to be ignored in residential applications, often with disastrous results. Shrinkage and small cracks not exceeding 1/8" that are not considered structural may be addressed by using crack isolation membranes conforming to criteria set forth in ANSI A118.12. Options here include simply isolating the existing shrinkage cracks or opting for complete coverage of the slab with the application of the membrane over the entire area. Details for these methods can be found in the TCA Handbook (F125 and F125A).

Plywood is also commonly used in interior applications and carries with it its own criteria for a successful installation. It should be used in only limited wet or dry areas. A waterproof membrane would be required in wet areas. Make sure the plywood is the proper thickness and quality and that the plywood subfloor it is adhered to was installed according to industry standards, including gapping the sheets 1/8" to allow for expansion and contraction.

When you stop to look at all the things that can go wrong with an installation, it is no wonder that there are not more failures out there occurring every day. It really comes down to proper design. Builders I talk to on a weekly basis are not really the enemy. Often times they do not understand our industry criteria. It is up to us to educate them. I truly believe they are as appalled at failures as we are. The biggest mistake we can make is to move forward and install tile on questionable substrates because we are afraid of being more expensive than the competition and losing work. I hear this all the time. I feel strongly that if you educate the builder or general contractor on these issues, and they wish to continue to install ceramic tile on inadequate or questionable substrates, this is a customer you do not wish to keep. I would like to believe this is the exception rather than the rule.