By Lesley Goddin
For this month’s Stone section, we went to Roy Viana, Dal-Tile Director of Natural Stone and Slab and Carlos Chiu, Dal-Tile Product Manager of Stone Tile and Sourced 
Mosaics to get an overview of issues pertinent to stone selection, maintenance, and installation for the professional tile contractor.
The first step in a stone installation is to select the stone, not just for aesthetics, but also to be sure the characteristics of the stone match the intended application.
Both Viana and Chiu agreed that natural stones – granite, marble, soapstone, limestone, travertine, etc. – all have specific technical characteristics that make them unique, and make them perform differently in a given setting depending on use and customer lifestyle.
Match stone to application
Chiu recommended knowing the place and type of environment in which the installation will take place – and suggested answering these questions in order to ensure the natural stone is a match for the application:
Is it an interior or exterior application?- Will it be subject to freezing and thawing conditions?
- Is slip resistance a concern?
- Will the stone be in contact with water or humidity?
- Will it be a floor or wall application?
- Is it a high or low traffic area?
- “Once you know the answers to these questions you will be able to narrow down the stones that are suitable for your application,” he said.
Viana added, “Take into account the color, pattern and texture of the stone, paying special attention to the larger overall appearance. Stone finishes, such as polished, honed, antiqued or leathered (to name a few), will play a significant role in the finished kitchen countertop selection.”
Don’t skip the sealer
When working with stone, be mindful of the need for a sealer, Chiu explained. “Most of the time, stone needs to be sealed before applying the grout and after applying the grout. Some other stones need the sealer to be applied on the six sides of the tile to prevent the stone from absorbing humidity and changing color.”
A sealer is important, Viana echoed, as an effective precautionary measure against damage caused by everyday use. “The sealer creates a protective layer over the surface of the stone, preventing liquid from being absorbed and causing discoloration,” he said. “Proper application of a sealer is extremely important.” It’s also important that the proper TYPE of sealer be applied, so become familiar with sealer options and consult with the stone supplier or sealer manufacturer to be sure the product will enhance – and not harm – the stone.
Porous and soft stone need special considerations
During the actual installation process, consider the stone characteristics before selecting setting materials. “For example, there are some stones that react to water and installing them with a regular thinset will cause the stone to curl,” Chiu said. “To prevent this, an epoxy needs to be used. In addition, some stones have reinforced backings, such as resin or mesh backings. Therefore, any stone with these types of backings needs to be installed with epoxy. Exterior applications sometimes require special setting materials.
“In terms of grouts, some stones – specifically soft stones with polished finishes – can get scratched easily if sanded grout is used,” Chiu added. “Therefore, unsanded grout needs to be utilized. However, there are limitations regarding what type of grout can be used based on the grout width. If your grout width is wider than 1/8”, sanded grout needs to be utilized. If the grout width is less than 1/8”, unsanded grout will need to be used. If your grout width is too wide to use unsanded grout, then use sanded grout but apply it carefully to prevent scratching.”
Keeping stone beautiful
Once installed, counsel your client on maintenance to ensure long life and beauty of the stone. “Keeping the surface clean is the golden rule of natural stone,” Viana said. “As a porous stone, it can be susceptible to stains and discolorations from various liquids, especially the acidic ones. Citrus juice, vinegar and common household cleaning products can cause damage to certain natural stone countertops, such as marbles.” Spills should be wiped up immediately.
Cleaning the stone should be done with specially formulated cleaning products designed for natural stone, Viana said. Also he suggested keeping stone away from toiletry products which may contain chemicals that damage stone. Keeping products on a mat or in a decorative basket can protect stone, as does using coasters on bathroom countertops.
“Being proactive about keeping your natural stone clean will significantly increase its longevity while maintaining its beauty,” Viana said.
Direct heat can also discolor stone, so stone countertops should be protected from hot pots, plates and pans by using trivets and mats as barriers between the hot items and the stone. “Bathroom counters are especially vulnerable to forgotten hair curlers or straighteners, which can burn, and even crack, some stone due to ‘thermal shock’,” Viana said.
With proper care, protection and preparation, stone can be suitable for almost every area. However, Chiu said that stone isn’t a suitable choice when it would be “submerged in water and the water contains some type of chemicals, such as chlorine. Pool or fountain chemicals will discolor the stone. Stone is suitable for all other types of applications. It is just a matter of finding the right stone, installing it correctly and maintaining it well.”
