roof

roof overhead covering of a building with its framework support. Various methods of construction, such as are suited to different climates, have diversified exterior and interior architectural effects. A roof may be flat, as in hot, dry areas where the shedding of rain and snow does not present a problem, e.g., in ancient Mesopotamia, Egypt, and in the SW United States. Modern structural materials and methods have made flat-roof construction practical in nearly any climate, with the development of concrete slabs, efficient drains, and waterproofing materials. On the other hand, steeply sloping roofs are still commonly found in N New England, in the Scandinavian countries, and in other regions where it is necessary to shed snow. Variations of the pitched roof are in gable, gambrel, mansard, or hip (having four sides sloping from a short ridge or center) form. The pitched roof may be of the lean-to type, as in a simple shed, or it may achieve the dignity and aspiration of a dome or spire and embody such features as the dormer window, cupola, or minaret. Pointed-roof construction includes the tie-beam, trussed-rafter, collar-beam, and hammer-beam types. English churches and halls afford many examples of these various methods, some of which have highly decorative open-timber interiors. The simplest roof covering is thatch (of straw, palm leaves, or other fibers) used by the peasants of many lands. Other finishing materials include wood (usually shingles), tile, slate, tin, lead, zinc, copper, felt, and tar. A roof's ridge is the point where the rafters meet; its principals, the purlins, resting on center or side posts, support the rafters; a valley or trough is formed by the junction of two slopes (e.g., where an ell joins the main structure). The eaves, or overhang, carry gutters or themselves drain water beyond the walls, and in the chalet and bungalow they are very wide. The concave curve of East Asian roofs is said to follow the graceful lines of a sagging tent. The classical Greek roof was of marble slabs upon timber framing and sloped gently. Early Roman roofs also were timber framed (as in the basilicas), but vault and dome construction (as in the Pantheon) were prominent in later buildings. The pointed arch and vaulting gave the slope to the Gothic roofs of Europe, while roofs in Renaissance Italy, except those with domes, were concealed, but France and Germany of this period emphasized the gable. Stepped gables are characteristic of Dutch and German roofs. Cone-topped turrets are common on the steep roofs of French châteaus. Roof ornamentation consisted of finials, crockets, crestings, gable crosses, bosses, and fantastic gargoyles (that also served as waterspouts). Roof decoration was particularly elaborate in early Asian and Gothic architecture. In contemporary architecture, roofs can span great distances with little material and few supports because of advances in the methods of using concrete and steel. Green roofs, which have used mainly since the late 1980s, lessen the environmental impact of traditional roofs, especially in urban areas. The roof surface of a building is covered with soil or another growing medium that is planted with grasses, flowers, or other plants. Green roofs reduce storm water runoff, reduce roof heating (mitigating urban "heat islands" and lowering cooling costs) and insulate the building (lowering heating and cooling costs).

Bibliography: See T. Hamlin, Forms and Functions of Twentieth-Century Architecture (1952).

roof / roōf; roŏf/ • n. (pl. roofs ) the structure forming the upper covering of a building or vehicle. ∎  the top inner surface of a covered area or space; the ceiling: the roof of the cave fell in. ∎  used to signify a house or other building, esp. in the context of hospitality or shelter: helping those without a roof over their heads they slept under the same roof. ∎  (roof of the mouth) the palate. • v. [tr.] (usu. be roofed) cover with a roof: the yard had been roughly roofed over with corrugated iron. ∎  function as the roof of: fan vaults roof these magnificent buildings. PHRASES: go through the roof inf. 1. (of prices or figures) reach extreme or unexpected heights. 2. another way of saying hit the roof. hit the roof inf. suddenly become very angry. raise the roof see raise. the roof of the world a nickname given to the Himalayas.DERIVATIVES: roof·less adj. ORIGIN: Old English hrōf, of Germanic origin; related to Old Norse hróf ‘boat shed,’ Dutch roef ‘deckhouse.’ English alone has the general sense ‘covering of a house’; other Germanic languages use forms related to thatch.

roof. Covering of any building by which its fabric and habitants are protected from the inclemencies of the weather. Roofs are here considered as to their form or type and finish, the structure of roofs being dealt with elsewhere. Cladding of roofs may be of metal (especially aluminium, copper, lead, iron, steel, and zinc), glass, slate, stone, thatch, tile, turf, wood, or other materials. Greek temples had marble roofs, the slabs worked to prevent leaks; the Romans used tiles; medieval churches were clad in lead, tiles, or thatched; and since C19 a variety of materials has been used. Barry's Palace of Westminster, for example, is clad in cast-iron panels.

Types of roof include:appentice: see lean-to;barrel: roof with internal appearance of a barrel-vault, like a cylinder;catslide: pitched roof covering one side of a roof and continuing at the same pitch over a rear extension, commonly found in Colonial architecture in New England (USA), where it is referred to as a saltbox. A catslide can also be the roof of a dormer pitching in the same direction but less steeply than the main roof;compass: see truss;cradle: see trusscurb: pitched gable-roof with the slopes broken to form two sets of planes on each side, the outer planes being steeper in pitch. Similar to a mansard roof, but with a curb or horizontal band with a vertical face at the junction between the two pitches;cut: see truss;double–: see truss;French: curb-roof with the sides set at very steep angles (almost vertical) and the pitched top part (gabled or hipped) almost flat;gable or pitched: commonest type with sloping sides meeting at a ridge and with a gable at each end;gambrel: in the USA curb roof with only the two sides sloping (i.e. a gabled curb-roof), but in Britain a hipped roof with a small gable or gablet under the ridge at one or both ends;half-hipped: pitched roof with gables terminating in hipped roofs;helm: with four sloping sides joining at the apex, like a pyramid, set on a square tower with gables the tops of which coincide with the lines of the junctions between the sides of the roof. The sloping sides sweep downwards over the raking tops of the gables, and terminate in points where the gables join;hipped: with four pitched slopes joining at hips, and without gables;lean-to: monopitched appentice, set against a higher wall, as over an aisle and against a clerestorey of a basilican church;M–shaped: with two parallel pitched roofs meeting in a valley or gutter;mansard: named after F. Mansart, a curb-roof with steeply pitched or curved lower slopes and pitched or hipped roof over, almost invariably with dormer-windows. Distinguished from the French roof in having a more steeply pitched upper part, and in the USA called gambrel;pavilion: hipped on all sides to have a pyramidal or almost pyramidal form, as pyramid-roof;penthouse: as lean-to, but not necessarily associated with a church, so a simple monopitched roof;pitched: as gable;pyramid: shaped like a pyramid or a hipped roof with a very short ridge so that the slopes almost meet at a point, as pavilion;ridge: any pitched roof with the sloping sides meeting at a ridge;saddleback: ordinary gable-roof on top of a tower;shed: as penthouse;single–framed: see truss;slab: flat roof consisting of one slab of concrete or of several concrete slabs joined together and spanning between walls;span: ridge roof of two equal slopes as distinct from a lean-to or penthouse-roof;suspended: web or webs hung on cable-nets stretched between heavy cables fixed to masts and the ground, as in Otto's work, called a tent-roof;tent: with a concave surface like a camp roof, or sloping inwards with a convex surface, such as the roof of a Regency balcony or a verandah; terrace: flat roof with imperceptible slope or fall, waterproofed, and permitting free use for sitting, etc.; trough: M-roof; valley: M-roof, or roof covering a building with projecting wings requiring valleys where the subsidiary roofs join the main roof. See also cruck; truss.

Bibliography

Nicholson (1835);
W. Papworth (1887);
Sturgis et al. (1901–2)