As the use of ceramic tile and stone spreads beyond the usual “wet areas,” specifiers and installers must adjust their designs accordingly.
Members of the A&D community continue to demand high performance from the beautiful ceramic tile and stone installations specified in their projects. Today, professional, specialized contractors are asked to install these finishes in more places than the usual "wet areas" generally characterized by commercial kitchens and bathrooms. Tile and stone can be used in virtually any room of any building for functional purposes, or simply for its beauty.
But due to the increased use of tile and stone in commercial interiors, builders have to adjust the way their structures are designed and built beneath ceramic tile and stone applications. Traditionally, it has been taken for granted that the structure could be of the same construct that is beneath hardwood, resilient or carpeted areas, but with the increasing popularity of large-format tiles and stones—and longer spans for larger rooms—failures
can occur if the structures are not designed properly. Builders must rely on strong interior design plans for these construction projects. The areas that receive ceramic tile and stone must be designed to a more rigid standard than those which are finished with other materials.
structural requirements for installations
Before any work starts, the surface must be rigid enough to accept the tile or stone. The TCNA Handbook for Ceramic, Glass and Stone Tile Installation, published by the Tile Council of North America, explains that it is the responsibility of the project architect, designer or engineer to determine if the substrate meets the proper stiffness and deflection criteria. The substrate needs to meet the maximum allowable deflection for the finish and the installation system that will be installed. Deflection is the potential movement which the installation may experience when subjected to load and use. Ceramic tiles and stones are very rigid and thus will not be able to handle excessive movement in the substrate. All substrates therefore should meet the maximum allowable deflection rating of L/360 for ceramic tile and L/720 for stone applications. Some adhesive manufacturers will allow an L/480 deflection standard for stone applications.
It is important to keep in mind that these maximum allowable deflection standards are very different from the L/360 design standard that is called for in most building codes. The building code requirement applies to a uniformly applied load across the spans, but it is not uncommon for ceramic tile and stone applications to be exposed to concentrated loads. A good example is when a person is walking over a structure wearing high heels. This exerts a tremendous concentrated force down upon a very small area. A person weighing 150 pounds and concentrating her weight load on a small heel is distinctly different than the same 150 pounds being uniformly distributed over the span of an entire floor. Appliances that sit on "legs" or wheels will also concentrate their weight load, as well. Therefore, when ceramic tile and stone floors will be exposed to concentrated loads, the engineer and/or specifier must specify a substrate to accommodate it.
Some other things to note: What will the areas that receive the tile and stone be used for? How many people will be using that area? The more people that will use a space, the more rigid the structure must be. A floor that is designed at a 40 pound total live and dead load may be suitable for usage by four or five people. But what if this business space changes and that same floor space is subsequently used regularly by 30 people? What may have been rigid enough for a small group of people is now being pushed beyond its deflection limits, which can cause cracking of grout, or even worse, cracking of tiles and stones.
Exterior glue plywood, cement backer units and concrete are the most common flooring types for builders. There are also many uncommon types which remodelers frequently come across. These include existing finishes like ceramic tile and stone or resilient flooring. They even run into substrates that still have old adhesives on them. Tile and stone are able to be successfully installed over certain types of uncommon finishes, provided that proper precautions are taken.
With all tile and stone installations, proper surface preparation is perhaps the most important phase of the work. Even when it needs to be specifically addressed, not enough time or resources are generally allocated to ensure that this is done correctly. This scenario is especially true in renovation work. (One never knows what one may run into when starting to renovate a commercial interior!) There are a few common requirements for all surface types relative to floor preparation, and they are generally related to the cleanliness of the substrate and its rigidity.
All substrates must be free of any bond-breaking or bond-inhibiting materials. These may include sealers, waxes, curing compounds, form release agents, paint, dirt, grease, oils, old carpet adhesives or other contaminants. They must be completely removed prior to the tile or stone installation. One of the best ways to remove these contaminants is via the mechanical abrasion method. Usually, the contaminants have penetrated into the substrate's pores and will block an adhesive's ability to create a mechanical bond or attachment to the surface. It is not a good idea to use chemicals or acid to strip/remove these contaminants. Chemicals or acids may penetrate into the substrate and will become virtually impossible to remove.
Commercial renovations present a potential number of problems. For example, if you find existing hairline cracks on a concrete substrate, what can you do? To best address this problem, use an anti-fracture membrane to help reduce the transmission of the cracks to the tile or stone. Protection from water damage is another area to be addressed. Although times are changing, most tile and stone used is still in wet areas of the interior. It is important to remember that tile, stone and grout are not completely waterproof. Today's buildings need to
be protected from potential water damage from spaces above or from adjacent areas. Most adhesive manufacturers provide thin, load-bearing membranes which are compatible with adhesive and grout mortars. Waterproofing membranes also protect the structure itself and the construction cavities against water damage, minimizing the potential for stain-causing mold and mildew.
An expansion allowance should also be included in all tile and stone installation systems. Exterior, wet area and installations exposed to direct sunlight will require more frequent and wider expansion joint placement. The designer should provide direction on the design, placement and construct of all expansion joints. If the designer cannot be on the jobsite, the TCNA Handbook for Ceramic, Glass and Stone Tile Installation provides information on the design, placement and construct of expansion joints.
For interior areas, the expansion joints should be placed every 20 feet in each direction in the field
of the installation, at all perimeters, against restraining
surfaces and at changes of plane. The sealant chosen for these joints should be durable, weather-resistant and able to handle any movement the installation will be subject to. Typically, silicones and urethane sealants are best for these applications. Most sealants produced will match the grout colors used. Latex or acrylic caulks should not be used for these applications. They are only suitable for interior, non-wet, non-traffic areas.
porcelain versus ceramic tile
Porcelain tiles are the most popular type of tile in use today. They have a very low porosity rate—generally less than 0.5 percent. A typical ceramic-bodied tile usually has a porosity rate of 3 percent, or even greater. This means that your adhesive mortar needs to have a greater ability to formulate a bond with the back of the much denser porcelain tile, or the mortar will not have the ability to penetrate or absorb into the body of the tile and mechanically "grip" it (like it can with a more porous ceramic-bodied tile). A conventional dry-set or low-end thin-set mortar will not provide the desired results for porcelain tiles.
For best results, specify a suitable, latex-fortified thin-set mortar to install porcelain-bodied tiles. These are ANSI A118.4 or ANSI A118.11-compliant thin-set mortars. The Tile Council of North America clearly requires that a latex-fortified thin-set mortar be used to install porcelain-bodied tiles. It is recommended that you check with your adhesive manufacturer for a single source comprehensive installation system that is fully warranted for labor and materials. This process will ultimately provide builders, renovators and end-users peace of mind for years to come.
What type of grout should be used in today's commercial interiors? Building owners and facility managers are demanding low-maintenance materials in every area of their structures. Floors, walls and countertop installations fall into this arena.
Historically, grout has been the hardest part of a tile or stone installation to maintain and keep clean. There are grouting materials which address this concern. Epoxy-based grouts are available and have a porosity rate of less than 0.5 percent, and therefore never need to be sealed. Just think of the labor and materials cost savings realized by not having to seal the grout every year. Today, a special cross-linking technology grout is also available with special features: it offers antimicrobial protection to inhibit the growth of stain-causing mold and mildew, and can even be specified with sparkling or glow-in-the dark features. This special grout provides all the benefits of epoxy grout and is as easy to install as cement-based grouts, making it a popular choice among customers. These grouting materials are
also included in the adhesive manufacturer's
comprehensive warranties. This adds great value to the final, completed building project.
There is a wealth of information available to commercial interior designers from the tile and stone industry. Our goal is to educate everyone associated with tile and stone installations, from the designers, builders and installers right through to the end-user. The more everyone knows about tile and stone, the better the installation will be—and successful installations are a good reflection on all of us.
Arthur Mintie is director of technical services with LATICRETE International, Inc., a global manufacturer and marketer of installation systems for ceramic
tile and stone used in residential, commercial and industrial applications. Visit www.laticrete.com for more information.