Roof tiles

Roof tiles can be affixed by screws or nails, but in some cases historic designs utilize interlocking systems that are self-supporting.

One of the simplest designs of roof tile, these are simple overlapping slabs installed in the same manner as traditional shingles, usually held in place by nails or screws at their top.

Early examples of this profile were created by bending a piece of clay over a worker's thigh, which resulted in the semi-circular curve.

[6] The origins of clay roofing tiles are obscure, but it is believed that it was developed independently during the late Neolithic period in both ancient Greece and China, before spreading in use across Europe and Asia.

[12] Spreading rapidly, roof tiles were found within fifty years at many sites around the Eastern Mediterranean, including Mainland Greece, Western Asia Minor, and Southern and Central Italy.

[14] While more expensive and labour-intensive to produce than thatch, their introduction has been explained by their greatly enhanced fire-resistance which gave desired protection to the costly temples.

[20] The Romans spread the use and production of roofing tile across their colonies in Europe, with kilns and tile-works constructed as far west and north as Spain and Britain.

In the twelfth century clay, slate, and stone roofing tile began to see more use, initially on abbeys and royal palaces.

The Scandinavian style of roof tile is a variation on the pantile which features a subdued "S" shape reminiscent of an ocean wave.

The five elements of fire, water, wood, metal and earth were common decorations during the Three Kingdoms period, and during the Goryeo dynasty Celadon glaze was invented and used for the roof tiles of the upper class.

Many post-war Korean roofs feature giwa and a common ornamental symbol is the Mugunghwa, South Korea's national flower.

[31] Metal roof tiles made of gold, silver, bronze and copper are restricted to religious architecture in South Asia.

[citation needed] Roof tiles were introduced to North America by colonizers from Europe, and typically were traditional designs native to their original country.

Spanish and French colonists brought their designs and styles of roofing tile to areas they settled along what are now the southern United States and Mexico, with Spanish-influenced tile fragments found in Saint Augustine, Florida, and both Spanish and French styles used in New Orleans, Louisiana.

[36] From the 1700s through early 1800s, clay roofing tile was a popular material in colonial American cities due to its fire-resistance, especially after the establishment of urban fire-codes.

The Marseilles tile pattern is distinguished from other designs by its diagonal notches on its side rebate, as well as the teardrop-shaped end of its middle-rib.

[39] While the Martin Brothers invented the design, its widespread use was more due to the pattern's adoption and international production after its original patent expired.

While visiting Grassau, Bavaria, Kroher learned about locals' use of regional minerals to create stucco and began to experiment with the material, developing a diamond-shaped interlocking pattern of concrete tile which became one of his company's primary profiles.

Concrete tiles became more widespread in Germany over the next few decades after manufacturers such as Jörgen Peter Jörgensen and Hartwig Hüser began producing interlocking and overlapping designs.

[54] The concrete tile industry grew and spread internationally through the early 20th century, driven by its cheapness to produce at scale.

[39] It is uncommon for a roof to be completely covered in glass tiles however there are a few exceptions, such as on the tower of Seattle's King Street Station.

Durability is directly related to three factors; a resistance to chemical decomposition, a low porosity, and a high breaking strength.

During a freeze-thaw cycle, water that infiltrates a tile will see volume expansions of 9% upon freezing, which exerts pressure within any pores it manages to enter and causes cracks to grow.

[73] A similar effect can be seen in areas near the ocean that experience salt-air intrusion, which can lead to salt crystal permeation and expansion.

[74] Clay tile porosity can range greatly depending on quality of production, but some manufacturers can achieve less than 2% moisture absorption.

Concrete roof tiles tend to feature around 13% moisture absorption, which requires periodic resealing every 3–7 years to avoid critical failure.

Over time some cultures, notably in Asia, began to apply glazes to clay tiles, achieving a wide variety of colors and combinations.

Many producers have shifted away from this process since low firing temperatures typically result in a higher porosity and lower breaking strength.

[80] The color of slate tiles is a result of the amount and type of iron and organic material that are present, and most often ranges from light to dark gray.

Due to the simple production process and comparatively low firing temperature, cement tiles fade over time and often require painting to restore a "new" appearance.