Since the arrival of COVID-19, both individually and in our businesses, we have looked for ways to keep our distance from each other. Using exterior spaces has become a common way of practicing social distancing. Homeowners are more likely to entertain guests on a back deck, or front porch. Restaurants seeking to stay in business and remain open use exterior spaces to accommodate diner’s and meet local health restrictions.
With all this movement outdoors, there has been an increased desire to dress up these areas which in turn has led to more exterior tile installations being done over the last year.
The ANSI (American National Standards Institute) standards, and the TCNA (Tile Council of North America) Handbook guidelines are different for exterior installations than for interiors. The reason for these differences: environmental conditions the installation will have to endure. The range of surface temperatures an exterior installation will experience far exceed those found in interiors. Exteriors are exposed to much greater amount of moisture and therefore require higher standards, and different techniques to extend the longevity of the installation.
Even when all industry standards, guidelines, and best practices are followed an exterior installation will not perform and last as long as an interior installation. This is one of the most important pieces of information I could provide a contractor performing exterior installations. As contractors our reputation for doing great installations that last is ultimately what keeps us in business. Navigating with a customer what to expect from their exterior installation and controlling their expectations is paramount to an exterior installation’s success.
Our industry standards and guidelines can help the contractor convey this message and control expectations. In the maintenance section of ANSI A108.01 3.9, it states “Maintenance of all tile installations and especially exterior installations require periodic inspection and maintenance. All exterior installations require inspection and routine maintenance including the application of hydrophobic sealers, repair of movement joints, and replacement of cracked or missing tile and grout. It is the owner’s responsibility to provide for routine inspection, and appropriate maintenance.”
In my proposal for exterior jobs, I would always include this quote from ANSI stressing the routine maintenance requirements. You should also recommend a post installation maintenance plan in addition to the original installation estimate. They say good communication makes for long friendships, and letting your customer know ahead of time in writing what to expect is a good business practice. You may change the customer’s mind about proceeding with an exterior installation, but it is better to have lost that one job than completed it and had an unhappy customer for years to come.
Exterior Installation Standards
First and foremost, mortar coverage requirements are higher for exteriors than interiors. Exteriors require 95% mortar coverage, where tile installed in interior dry areas only require 80% mortar coverage. The need for mortar coverage is essential in exterior installations because of their exposure to water and the freeze-thaw conditions found in most parts of the United States. When water collects underneath or behind the tile and the temperature drops below freezing the water expands and is destructive to the tile assembly.
This can also cause efflorescence, generally seen as a white powdery substance on the surface of grout joints, which leaches over on top of tile surfaces. Efflorescence occurs when water trapped behind the tile is heated up as the moisture tries to escape the space usually through the grout joints, it pulls salts with it leaving the distinctive white powder on the surface of the installation. Managing the water is the best way to eliminate issues with efflorescence. Using the right trowel with the correct troweling technique, and back buttering can all help to achieve 95% mortar coverage, which decreases the area water can collect and create these problems.
Another important aspect of any exterior installation is picking the right materials for the job, not all tile, mortar, and grout is approved for use on exterior applications. Always check with your manufacturers about product suitability before starting any project.
Jobsite conditions are critical for success in exterior installations. Many installers use ambient air temperatures as their guidelines for exterior installations. The surface temperature of substrates and materials used should also be checked before installation begins. In the Summer, the air temperature can be in the low 80 degrees F, but the surface temperature of exposed concrete can be well above 100 degrees. Checking the surface temperature can be easily done with a laser thermometer. Most setting material manufacturers require surface temperature ranges of 50 – 90 degrees F.
To reach this range sometimes requires outside of the box thinking and will differ in different parts of the country. In the Midwest, we would do installations in the pre-dawn and early morning hours. You can also use tarps to reduce the sun’s effect on surface temperature or mist the substrate with water prior to installation to cool the surface. Wind can also create issues with mortar skinning over, and grouts flash drying. Selecting the right time or creating the right environment for the setting materials to work as they are designed will help you be successful.
Movement accommodation joints are essential for successful installation. ANSI and the TCNA handbook state movement accommodation joints should be used at a maximum of every 12’ exteriors. TCNA section EJ171 states under location and frequency “Exteriors – 8’ to 12’ in each direction” and under Joint width “The width shall be 3/8” for joints 8’ on center and a minimum of 1/2” for joints 12’ on center. In addition, for every 15 degrees F over 100 degrees F from Summer high to Winter low, an additional 1/16” must be added to the joint width. For example, with an exterior installation which will sustain a 130-degree temperature change from Summer high to Winter low, you would need to add an additional 1/8” to the suggested joint width.
In conclusion, if your exterior installation is completed according to industry standards there will be maintenance required for that installation and it is the owner’s responsibility to make accommodations for the inspection and maintenance. The contractor is best served if he communicates this to the owner prior to the installation.
The mortar coverage requirements for exterior installations are higher and require the right trowel, technique, and back buttering. Make sure your materials and jobsite conditions are correct for success. Install movement accommodation joints in your exterior work they are a requirement and our paramount to having a successful installation. I hope this information is helpful next time someone asks you to take it outside.
About the Author:
Robb Roderick is a technical trainer for the National Tile Contractors Association. He travels the United States holding workshop and educational programs teaching tile industry standards and methods. Robb is certified as an Installer by the Ceramic Tile Education Foundation. He has 30 years’ experience in the tile industry working with architects, designers, builders, and homeowners in thousands of both residential and commercial projects. He earned a Bachelor of Science degree from Missouri State University in 2000.