Timber lends itself to a great variety of roof shapes. In countries that use bamboo extensively, the flexibility of the material causes a distinctive curving line to the roof, characteristic of Oriental architecture. The supporting structure of a roof usually comprises beams that are long and of strong, fairly rigid material such as timber, and since the mid-19th century, cast iron or steel. The roof structure is generally supported upon walls, although some building styles, for example, geodesic and A-frame, blur the distinction between wall and roof. In a minority of buildings, the outer layer is also a self-supporting structure. There are two parts to a roof: its supporting structure and its outer skin, or uppermost weatherproof layer. Some roofs follow organic shapes, either by architectural design or because a flexible material such as thatch has been used in the construction. Pitched roofs, including gabled, hipped and skillion roofs, make up the greatest number of domestic roofs. Roofs constructed of flat sections that are sloped are referred to as pitched roofs (generally if the angle exceeds 10 degrees). There are many variations on these types. Mono-pitched, gabled, mansard, hipped, butterfly, arched and domed. The main factors which influence the shape of roofs are the climate and the materials available for roof structure and the outer covering. The shape of roofs differs greatly from region to region. The durability of a roof is a matter of concern because the roof is often the least accessible part of a building for purposes of repair and renewal, while its damage or destruction can have serious effects. Drainpipes also remove the need for a sloping roof.Ī person that specializes in roof construction is called a roofer. In regions where there is little rain, an almost flat roof with a slight run-off provides adequate protection against an occasional downpour. Other types of roofing, for example pantiles, are unstable on a steeply pitched roof but provide excellent weather protection at a relatively low angle.

Some types of roofing, for example thatch, require a steep pitch in order to be waterproof and durable. So the pitch is partly dependent upon stylistic factors, and partially to do with practicalities.

Although modern construction elements such as drainpipes may remove the need for pitch, roofs are pitched for reasons of tradition and aesthetics. Most US domestic architecture, except in very dry regions, has roofs that are sloped, or pitched. The pitch is the angle at which the roof rises from its lowest to highest point. The construction of a roof is determined by its method of support and how the underneath space is bridged and whether or not the roof is pitched. Other roofing materials include asphalt, coal tar pitch, EPDM rubber, Hypalon, polyurethane foam, PVC, slate, Teflon fabric, TPO, and wood shakes and shingles. In many parts of the world ceramic roof tiles have been the predominant roofing material for centuries, if not millennia. The material of a roof may range from banana leaves, wheaten straw or seagrass to laminated glass, copper (see: copper roofing), aluminium sheeting and pre-cast concrete. The elements in the design of a roof are: 'English alone has retained the word in a general sense, for which the other languages use forms corresponding to OE. There are no apparent connections outside the Germanic family. Dutch roef 'deckhouse, cabin, coffin-lid', Middle High German rof 'penthouse', Old Norse hrof 'boat shed'). Old English hrof 'roof, ceiling, top, summit heaven, sky', also figuratively, 'highest point of something', from Proto-Germanic * khrofam ( cf.

Galleried ell