Tile is one of the most decorative forms of roofing, offering endless ornamental possibilities, thanks to the variety of available shapes, colors, patterns, and textures. Tile is also among roofing's most durable materials—it doesn't burn or rot, deteriorate from salt spray in coastal areas, or heat in the desert, and rodents and bugs don't chew on it. Is it any wonder, then, that clay tile roofs can last anywhere from 50 to several hundred years?
The two biggest enemies of tile roofs are falling tree branches and humans. Why humans? Because people are the culprits behind bad tile installations and faulty maintenance; they also often don't know how to properly walk across tile roofs without breaking them. The main downside of tile roofing, in fact, is its steep upfront costs. But, when spread out over a roof's long lifespan, tile is actually economical.
Tile Through Time
Clay tiles have deep historical roots. In China, tiles dating back to 10,000 B.C. have been found, and they appeared in the Middle East a short time later. Tile roofing traditions arrived to the U.S. through European settlers—via the Dutch on the East Coast around 1650 and through Spanish missionaries on the West Coast in the 1700s. Clay tiles were molded by hand until about 1870, when they began being manufactured by machine extrusion.
Historically, clay roofing tiles were categorized by their general shapes. The two basic tile types are rounded pan tiles and flat tiles. Pan tiles include the familiar barrel (or Mission) tiles, and Spanish tiles; they also encompass designs where two flat tile pieces are overlapped by a single curved tile, like Roman and Greek varieties. Flat tiles are referred to as slab, shingle, book, or French. Both pan and flat tiles can overlap or interlock when applied, depending on how they are designed. Interlocking tiles have an extrusion or lip on one tile that hooks over an edge or channel on an adjacent tile. Overlapping tiles, if flat, are applied with staggered joints in overlapping courses like shingles or slates. With pan tiles, the convex "cap" tiles overlap the concave "pan" or "trough" tiles on both sides. S-tiles, often called Spanish, combine the pan and cap into a single tile. Specialty tiles are required for ridge caps, starter tiles (sometimes called bird stops), and odd spaces at roof hips, rakes, or dormers. These can be highly decorative. Some roof shapes, particularly conical towers or turrets, require tiles in graduated sizes.
Unglazed clay tiles range in color from terra cotta to buff, brown, even pale pink. Tiles were sometimes treated with a manganese solution before firing to produce a black, brown, or bluish scorch mark on the surface. They also can be colored using slip (thin, runny clay). But the most expensive way to color roof tile is with glazes. As with indoor tiles, almost any color is possible, though historically, color preferences leaned toward greens, blues, and occasionally purples.
Concrete roof tiles are a much later invention. They became available in the U.S. around the turn of the 20th century, but concrete roofing didn't become widely used until decades later. Concrete tiles were molded by hand until the 1920s, but now they are extruded. The one exception is the Hendricks Tile Company of Richmond, Virginia, which still makes concrete tiles by hand.
Initially, concrete tiles were colored with iron oxides to imitate the red of terra cotta tile, the brown of wood shakes, or the grays and greens of slate, and earth tones remain the most popular colors. Concrete tiles were often used in the early to mid-20th century as more durable alternatives to wood, and more cost-effective alternatives to slate roofs.
Tile roofs, though found on just about every style of building, are commonly associated with architectural approaches rooted in Spain, like Mission, Adobe, and Pueblo Revival. But tile roofing options extend far beyond Spanish influence. Tiles resembling slate are often seen on Period Revival homes like Tudors or Normandy cottages. Some bungalows and Craftsman-style houses employed tile roofs, particularly the iconic Chicago bungalows. A few famous homes feature gorgeous tiled roofs, such as Gustav Stickley's home at Craftsman Farms and numerous Frank Lloyd Wright-designed houses. Handmade concrete shingles have been used in restoration projects at Colonial Williamsburg, Old Salem Village in North Carolina, and in many National Park Service projects.
Weight for It
Tile is heavy, but not as heavy as you might think. A roof strong enough to hold three layers of asphalt shingles could probably also stand up to the weight of tile. Clay tile generally weighs more than concrete, anywhere from 1,000 to 1,500 pounds per square (a square equals a 10'-by-10' area). Regular concrete tile weighs from 900 to 1,200 pounds per square, while newer lightweight concrete tile comes in at under 600 pounds per square, below the level at which many jurisdictions require a consultation by a structural engineer. When in doubt, it's a good idea to consult an engineer anyway.
Up until the mid-19th century, tiles were hung on horizontal battens using oak pegs, with no sheathing or building paper. This made it easy to find leaks and make repairs, but meant depending entirely on the tiles to keep water out. Eventually, tiles were nailed directly to wood sheathing, or hung on battens nailed to the sheathing using lugs or nibs molded into the back. Barrel tiles were often nailed to vertical battens, with cap tiles attached with wire. Ridge and trim tiles were often mortar-set.
Modern roofing practices lay tiles on 1"-thick sheathing with (at least) 30 pound felt or built-up roofing underneath, and a minimum slope of 3 in 12 (rising 3 inches for every foot). In areas prone to hurricanes or tornadoes, tiles must not only be nailed, but also attached to steel clips to prevent uplift in high winds. Hips and ridges are mechanically fastened and also adhered with polyurethane foam adhesives, which were found to bond better than mortar. Concerns about the performance of tile roofs during earthquakes have been allayed somewhat by a recent University of Southern California study, which found that tile roofs installed to uniform building code requirements withstood up to twice the forces required by code.
Flashing in the Pan
Fastening systems often give way before the roof—iron nails can rust out, so copper nails and wire or stainless steel screws are the recommended fasteners. Flashings and gutters must be the best quality metal—at least 16-ounce copper or lead-coated copper—in order to be as long-lasting as possible. Still, on a roof that's been up a hundred years or more, it's likely that the flashings and underlayment have deteriorated, requiring that all tiles be removed to replace them.
Installation and repair of tile roofs is a job best left to professional roofers experienced in working with tile. A new installation is straightforward, but repairs, re-roofing, or adding additions on existing tile roofs may involve finding salvaged tiles to match the originals. Given the variety of shapes and colors that have been available for the past 300 years, it's amazing that anyone manages to find a match, but they do. It helps that three companies—Gladding-McBean, Boston Valley Terra Cotta, and Ludowici—are still producing clay tile in many traditional shapes and colors, and can also re-create their vintage patterns. Finding matches may also involve dealing with salvage tile vendors, and some colors and profiles will be easier to find than others. Red Mission or Spanish tiles are more common than glazed French tiles, for example.
Whatever you do, don't let a roofer talk you into replacing a tile roof with asphalt shingles. It may be cheaper in the short run, but it will never look right or last as long. Tile roofs are distinctive, often dominant, features of historic buildings. Take them away, and your house will never be the same. Having a tile roof is a lot like owning a parrot—both are beautiful, exotic, expensive, and sometimes difficult to deal with. And both will probably outlive you.