Roofs are a significant element in the construction of any structure and provide a vital role in protection against wind, rain, solar radiation, snow, noise and dust. They also control the indoor environment by regulating temperature, moisture and the transmission of sound. They can also provide shelter and privacy as well as safety for occupants and property.
The term building, or edifice, is generally used to describe any enclosed structure with walls and a roof standing permanently in one place. There is a very wide range of buildings in the world and they come in all shapes, sizes and functions and are constructed from a vast array of different materials.
In the field of roofing, the word has become synonymous with any structure that covers and protects a structure above the ground and is intended to remain in one location, although this definition would exclude a tunnel or bridge. Roofs cover a range of structures, from simple shelters made of animal skins draped between sticks through to complex modern structures such as aircraft hangars and skyscrapers.
Throughout the 19th century the construction of domestic roofs changed little. The basic idea was to provide a structure above living accommodation with sloping timbers known as rafters fixed, at the top to a ridge board and, at the bottom, to a wall plate. Ceiling joists then supported the ceiling and, in some houses, a binder ran at right angles to the rafters to prevent rafter feet from spreading.
By the early 1900s timbers aceroofingandbuilding.co.uk were being cut more and more accurately and fixings in the form of nails, screws or bolts began to be replaced by more durable clips. These were soon followed by sheet metal or lead flashings to protect against water ingress and a variety of shingles, slates or tiles to give a decorative finish.
More recently trussed rafters have been introduced. These avoid the need for internal loadbearing walls upstairs and allow greater spans to be achieved. They are still often found in new ‘cut’ or traditional roofs. They are now normally manufactured from softwood and pre-treated to guard against rot or insect attack.
Modern roofs are usually insulated and protected by either mineral wool or cellulose (recycled newsprint) in a range of configurations. Both have higher compressive strength than fiberglass but cellulose has the disadvantage of being easily damaged by moisture. The use of a cover board is essential if this material is chosen and it should be specified to have high fire resistance. In the selection of insulation it is important to consider life-cycle cost as this will affect energy consumption, maintenance and repairs costs.