Tyler Allwood, Director of Technical Services and Systems for Eagle Roofing Products
In my opinion, tile roofing is the most popular steep-slope roofing product in the world. For thousands of years, tile has graced the roofs of homes, houses of worship, universities and commercial structures. In many parts of the globe it is the primary choice for roofing.
Why has tile roofing remained so popular throughout the millennia? There are many reasons. Tile is beautiful, distinctive, long-lasting, strong and safe. Not only does it enhance the curb appeal of a building, it also provides protection from the most extreme weather conditions. Because it is a natural product made from some of the strongest materials, it will continue to provide that protection for a long time.
For much of its history, roof tile was generally understood to be round and red, perfect for Mediterranean and old-world architecture. While tile remains ideal for an old-world look, innovations in the last 100 plus years have allowed the tile industry to create products that are perfect for any architectural style.
In order to fully comprehend the benefits of roof tile, it is important to know more about the two prevailing types of roof tile, clay and concrete. There are definite differences between clay and concrete tiles, mostly in their construction. However, both clay and concrete tile provide many of the same benefits to the building owner, namely a beautiful roof that will stand the test of time.
Clay roof tile is believed to have originated in China around 10,000 BC. Clay tile was also used by most early civilizations, including Greece, Ancient Rome and Egypt. As in these early times, clay roof tile is still made from earthen clay that is formed into molds and
fired or baked in kilns. Clay is very dense and non-porous making it an excellent product for roofing.
The production process for clay roof tile varies. Some tiles are still molded by hand and baked in brick ovens in small villages. Then there are modern companies using advanced technology to create precise interlocking tiles. As one might expect, the production process effects the look and strength of the final product and there are different grades of clay roof tiles, culminating in Grade 1, as
determined by ASTM C-1167.
In addition to earthen clay, companies may use additives to enhance strength or coloring agents to expand their offering. They may also use a specialized firing process to create a harder product that can stand up to more extreme weather. As with any roofing product, it is important to consider the environment where the roof is to be installed in order to select the clay tile that meets the
needs of the project.
Clay roof tile is available in many profiles, sizes, shapes, colors and finishes. Often referred to as terracotta tiles, clay roof tiles have broken free of traditional red or orange pan and cover design. They are available in a multitude of variations of “S”, flat and roll profiles. Colors span the spectrum from the traditional reds to bright glazed ceramic finishes. The broad variety of these tiles is on display around the country and they are often found on university, government and historical buildings, including the Supreme Court.
In the early to mid-nineteenth century a process called hydration – that occurs when aggregate, cement and water are combined, was discovered. This innovation would forever change construction throughout the world. What can be described as an early nanotechnology, due to the molecular changes that occur in cement during hydration, ushered in an incredibly strong and affordable material with endless possibilities and uses. Shortly after the discovery of concrete, the first concrete tiles were created in Germany and over the following century improvements to the production process have led to the
concrete tile roofs that are so popular today.
In modern manufacturing facilities, concrete roof tiles are made by combining Portland cement, aggregate and water, as well as coloring agents and in some cases various additives. The mixture is then extruded onto molds and sent into a kiln. The extrusion process was an important innovation, as it makes concrete roof tile denser and less porous. While more porous than clay roof tile,
concrete roof tile does have to pass a water absorption test, as well as a permeability test.
Concrete roof tiles are available in three main profiles: high, medium and flat. High profile tiles are often called “S” or high barrel tiles and are meant to emulate a traditional pan and cover. Medium profile tiles are sometimes referred to as roll or medium barrel tiles. Flat profiles are available in many textures and finishes and are often used to emulate slate or cedar shake roofs.
In addition to different profiles, there are different coloration processes available. Concrete roof tiles can be made with through-body coloring, known as color through, or with a slurry or color bonded surface coating. Color through tiles are made by combining the coloring agents with the aggregate, cement and water before extrusion and are basically the same color on the top and bottom of the tile. Slurry is a combination of the coloring agent, water, cement and a small amount of fine sand that is applied to the surface of the tile after the extrusion process. Most often, the tile below does not have any color.
Because the process for making concrete roof tile is easily automated, it is very flexible. This allows manufacturers to produce tile in any shape, texture or color quickly. The end user benefits from the value that this affords while receiving a beautiful and strong roof.
While clay and concrete tile have different constructions and production processes, the installation of the two types of tile is very similar. In fact, for basic installations, the Tile Roofing Institute (TRI) has compiled and combined the installation instructions for manufacturers of both types of tile. The Tile Roofing Institute is the association of tile manufacturers in the United States. Its role is to aid in the testing of concrete and clay tile, aid in the development of codes, publish installation manuals, train and certify installers of clay and concrete tile and advocate for clay and concrete tile manufacturers.
The TRI publishes three manuals: the TRI Concrete and Clay Roof Tile Installation Manual, the FRSA-TRI Florida High Wind Tile Installation Manual, Revised 5th Edition and the TRI Cold & Snow Concrete and Clay Tile Design Criteria for Cold and Snow Regions.
More information and all of the manuals are available at www.tileroofing.org.
In the past each manufacturer had its own installation instructions. Often these instructions differed, making it confusing for installers to know which instructions to use when. Now there is a single resource that is recognized by code bodies and building officials and promoted by the manufacturers. Additionally, there are many opportunities for training in the intricacies of the manual.
Clay and concrete roofs are beautiful and have the potential to outlast the building on which they are installed. However, it is imperative that they be viewed as part of a roof system. If the other components of the system are not appropriate or do not perform, it will not matter how long the tile lasts.
The other parts of the system are often called components or accessories. These include underlayments, flashings, vents, fasteners, etc. Every part of the system is important to the performance of the entire system. The underlayment prevents any water that enters under the tile from entering the attic space. Flashings protect any intersections, such as head walls or side walls, from
water intrusion. Vents ensure that there is proper air movement trough the attic or under the tile. The fasteners provide the necessary resistance to wind.
Each of the TRI installation manuals provides details and instructions for proper installation of the components as well as specifications for the proper materials. Often manufacturers provide some of these component products as well as guidance for a properly installed system.
A growing area of focus in the roofing industry is energy efficiency. It is generally accepted that hot attics and their effects on HVAC systems are the major causes for energy losses in buildings. More and more energy efficient products are produced every year to combat this problem.
Concrete and clay roof tiles have a clear advantage. Studies have shown that the air space below the tile as well as the higher thermal mass of these products can considerably reduce energy loss when compared to other lighter products. These properties act similar to insulation. Additionally, many colors of concrete and clay tiles are highly reflective, meaning that a large amount of UV energy is immediately repelled before it can work its way through to the attic.
With their many qualities, concrete and clay roof tiles will continue to expand their reach across North America. These natural products provide the beauty to meet any architectural demand, the strength to withstand all weather conditions and the durability to stand the test of time. They will also provide the perfect platform for the future of energy efficiency.
Tyler Allwood is the Director of Technical Services and Systems for Eagle Roofing Products. Tyler was a Florida roofing contractor prior to joining Eagle, serves on FRSA’s Roof Tile Committee and served as President of the Sarasota/Manatee affiliate of the FRSA.
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