The roof is the essential layer of protection between a building and the forces of nature. When used in the steep-sloped form popular for most residential buildings, the roofing material is also a key element of the building’s character. The essential need for this material and its role in design produced a strong market for roofing materials with a wide range of performance and visual characteristics. The APT Building Technology Heritage Library contains more than 600 documents under the subject of roofing, which also includes accessories such as gutters, downspouts and flashing.
The use of wood shingles, slate shingles and clay tiles were the dominant roofing materials until the mid-19thcentury. The development of bituminous and metal roofing systems were innovations that made the low-slope roof possible. For most commercial buildings, the roof has disappeared from the architectural view. During the 20th century a wide range of new roofing materials were developed for both low and steep-sloped roofs. The ubiquitous asphalt shingle had its debut in 1900 and is still the most popular roofing material for homes. The asphalt shingle evolved to the common three-tab version popular today after a period of various shapes, patterns and textures. Composite materials such as asbestos and fiber cement shingles represent products that promised better performance but also tried to replicate traditional materials such as slate or clay tile. Metal shingles that replicated clay tiles or asphalt shingles that tried to simulate thatch reveal a common design trend of simulation. The development of roofing materials with various levels of durability and fire resistance were important technical innovations.
The use of built-up roofing with a combination of asphalt coatings and asphalt-impregnated layers was a major roofing innovation that literally changed the shape of buildings. The steep-slope roof could be eliminated, which would have a great impact on the street-form and the scale of the built environment. The Barrett Mfg. Co. was a major producer of these materials. The BTHL features technical catalogs from the company from the 1890s through the 1950s.
The use of corrugated steel panels for roofing was popular for industrial and agricultural buildings. The extensive catalog of metal roofing products includes flat lock and standing seam metal roofing, corrugated panels and stamped metal tile. This catalog also has many roofing specialties including ornamental metal cornices.
The R. M. Reynolds Company of Grand Rapids, Michigan claimed to be the inventor of the asphalt roof shingles c. 1900. Like many common products, this is a rather difficult origin to prove. Rolled asphalt roofing coated with slate granules were available by the late 19th century so it wasn’t much of an innovation to produce these as individual shingles. Asphalt shingles were widely available by 1910 and rapidly replaced wood shingles because of their economy and improved fire resistance. The evolution of the asphalt shingle in the 20th century included a range of shapes and textures and the replacement of the crushed slate with ceramic granules.The Book of Roof, 1923
The combination of asbestos and cement resulted in an extremely durable roofing shingle that was much lighter in weight than clay tile or slate roofing. Fiber-cement shingles that simulated the look of slate and clay tile were particularly common. Another popular variation was a large-scale hexagonal unit that produced a distinctive pattern.
“Bonanza ‘Cementile’ are very large, steel-reinforced cement roofing, all factory-made and cured --- a specialized product brought to its highest stage of development. They are furnished in three distinct types, Interlocking Tile, Flat Tile, and Channel Tile, and all the necessary trimmings such as Ridge Tile (of various types), Skylight or Glass Insert Tile, Flashing Tile, Collar Tile, etc.”
The small manual is a useful survey of various roofing shapes and the appropriate use of copper roofing. Copper was promoted for its durability and light weight. However, it was also a very expensive material and found more use in institutional structures.
Clay tile roofing is one of the oldest forms of roofing, still available today in both its traditional materials and modern substitute materials. This Ludowici-Celedon catalog from the mid-1920s noted the “ancient” origin of this material. It was particularly popular when used with residential architecture in Spanish and “Mediterranean” styles popular in the southwest.
The era of the 1920s was a particularly dramatic period for asphalt shingles with a great variety of shapes and colors. This catalog features bold colors and patterns of asphalt shingles with many examples of polychrome installations.
Slate quarries in the northeastern part of the U.S. and nearby Canada made this a regionally important roofing material. Its use in the U.S. was common in several period residential building styles. Slate is extremely durable, which made it popular with institutional owners. The material was quite heavy, which lead to its preference in steep roof shapes. Slate was available in a limited range of colors. Red slate was the rarest and therefor used for more ornamental accents rather than complete roofs.
Stamped sheet metal roof tiles could be produced to simulate flat or curved clay tile in both individual and larger panels. This was a very popular material in the early 20th century. The W. F. Norman Co. of Nevada MO was an early producer of these materials. They still produce two simple versions of these metal roof tiles.
Steel roofing panels produced in larger sizes were particularly popular for agricultural and industrial buildings. The use of corrugated panels improved the span, which reduced the material and framing weight. The use of galvanized coatings gave these a long life. Galvanized and corrugated panels had its origins in the 19th century but is still available today.
In the mid-20th century, asphalt shingle reached a maximum of different shapes, textures and color blends. The use of ceramic granules for the surface increased the range of colors while improving fire resistance. The use of textures to simulate wood grain or colors to simulate clay tile were design variations. Asphalt shingles were promoted for their design, economy and durability. They were the most common roofing material for residential buildings for decades.
Wood shingles of cedar were one of the most common residential roofing materials of the 19th century. In the 20thcentury, asphalt shingles rapidly replaced the wood shingles for most residential buildings because of their economy and improved fire resistance. Cedar shingles continue to be used for roofing in more rural locations as well as a siding material, particularly in the northeastern U.S.