Cavemen needed some sort of shelter from the weather and elements in order to survive. Even though their sod and plant covered roofs were well insulated and kept them warm, it did not keep out the rain or vermin. If a caveman did not find an empty and waterproof cave, he had limited resources to build his own roof. Every civilization used whatever materials and tools were available to create their roofs. We can learn a lot about the creativity and advanced technology of a civilization by their roofs.
The first technologically advanced roofing material started in China 5,000 years ago. Their glazed clay roofs were followed 1,000 years later by the earthenware flat tile roofs of the Greeks and Babylonians. The Romans brought a variation of these tiles to England around 100 B.C. Made with plant covered sod on arches, The Hanging Gardens of Babylon were one of the seven wonders of the world in 500 B .C.
What seems like a step backwards, but it was more a reflection of what was locally available; thatched roofs were developed in 735 A.D. Wood shingles followed three hunded years later, but they were barely less fireproof than thatch. King John made it a law to switch from wood, thatch, or reed roofs to clay tiles in the 12th century to reduce the risk of fires and its spread from house to house.
Technological advancement continued with the development of dreadnaught clay tiles in 1805. Clay tiles were produced industrially in the nineteenth century, and one hundred years later concrete roof tiles were created with pigment added to look like clay roof tiles. Asphalt also became available for use in the nineteenth century, and it was popular because it could be mass produced at a reasonable cost.
The green roof system was developed in Germany in the 1960′s. Different from the Babylonian Gardens, these roofs had either thin or thick layers of soil on top of the roof structure then covered with a variety of plants. Whether a roof was pitched or flat was determined by the architecture and drainage needs. Buildings with arches, domes and vaults demanded a more elaborate and pitched roof than a commercial building in a drier climate.
Temperature, water, and humidity affect a roof that needs to cover buildings and protect the interior from wind, snow, rain and extreme temperatures. The earliest roofs used clay or a similar substance to put between the wood to make them waterproof. Modern day advances include a water protective sheet laid underneath the shingles or flat pieces of waterproof material.
In the last two hundred years, slate and felt became the most common building materials. Location plus available materials still dictate the type of roofing seen in Northern America. Slate roofs dominate buildings in the Northeast, and wood roofs are found in the Midwest. Tile roofs are seen in the Southwest, and wood and metal roofs are preferred in the South.
Technological advances continued with the development of smog absorbing tiles and roofs using glass polymer. With the concern over the environment and energy saving, we could see some earth friendly materials in the near future. These and future advances may transcend the use of local materials and customs as wood becomes scare and consumers more ecologically savvy.