Roof

The roof of a garden conservatory protects plants from cold, wind, and rain, but admits light.

Old English hrof[2] 'roof, ceiling, top, summit; heaven, sky', also figuratively, 'highest point of something', from Proto-Germanic *khrofam (cf.

Dutch roef 'deckhouse, cabin, coffin-lid', Middle High German rof 'penthouse', Old Norse hrof 'boat shed').

Other roofing materials include asphalt, coal tar pitch, EPDM rubber, Hypalon, polyurethane foam, PVC, slate, Teflon fabric, TPO, and wood shakes and shingles.

In regions where there is little rain, an almost flat roof with a slight run-off provides adequate protection against an occasional downpour.

[4] The basic shapes of roofs are flat, mono-pitched, gabled, mansard, hipped, butterfly, arched and domed.

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.

In countries that use bamboo extensively, the flexibility of the material causes a distinctive curving line to the roof, characteristic of Oriental architecture.

The stone arch came into extensive use in the ancient Roman period and in variant forms could be used to span spaces up to 45 m (140 ft) across.

The stone arch or vault, with or without ribs, dominated the roof structures of major architectural works for about 2,000 years, only giving way to iron beams with the Industrial Revolution and the designing of such buildings as Paxton's Crystal Palace, completed 1851.

With continual improvements in steel girders, these became the major structural support for large roofs, and eventually for ordinary houses as well.

In vernacular architecture, roofing material is often vegetation, such as thatches, the most durable being sea grass with a life of perhaps 40 years.

In areas with an abundance of timber, wooden shingles, shakes and boards are used, while in some countries the bark of certain trees can be peeled off in thick, heavy sheets and used for roofing.

While this method is faster, it does not allow the roof sheathing to be inspected and water damage, often associated with worn shingles, to be repaired.

The greatest concern with this method is that the weight of the extra material could exceed the dead load capacity of the roof structure and cause collapse.

[6] Slate is an ideal, and durable material, while in the Swiss Alps roofs are made from huge slabs of stone, several inches thick.

[7] Asbestos, usually in bonded corrugated panels, has been used widely in the 20th century as an inexpensive, non-flammable roofing material with excellent insulating properties.

Health and legal issues involved in the mining and handling of asbestos products means that it is no longer used as a new roofing material.

Both are expensive but durable, the vast copper roof of Chartres Cathedral, oxidised to a pale green colour, having been in place for hundreds of years.

In the 19th century, iron, electroplated with zinc to improve its resistance to rust, became a light-weight, easily transported, waterproofing material.

To protect the building interior from the effects of weather elements such as rain, wind, sun, heat and snow.

Most roof materials will last long after the manufacturer's warranty has expired, given adequate ongoing maintenance, and absent storm damage.

The purpose of a ceiling is to insulate against heat and cold, noise, dirt and often from the droppings and lice of birds who frequently choose roofs as nesting places.

The large area of a roof repels a lot of water, which must be directed in some suitable way, so that it does not cause damage or inconvenience.

[10] Standing water on a roof can lead to mold growth, which is highly damaging to both the building’s structure and the health of its occupants.

[11] Similar problems, although on a very much larger scale, confront the builders of modern commercial properties which often have flat roofs.

In parts of North America such as Buffalo, New York, United States, or Montreal, Quebec, Canada, there is a required minimum slope of 6 in 12 (1:2, a pitch of 30°).

There are regional building styles which contradict this trend, the stone roofs of the Alpine chalets being usually of gentler incline.

Most modern roofs and many old ones have systems of valleys, gutters, waterspouts, waterheads and drainpipes to remove the water from the vicinity of the building.

More complex systems may carry out all of these functions: generate electricity, recover thermal energy, and also act as a roof covering.