Roofing is the covering of a structure, such as buildings, with all materials and structures needed to support it upon the surface of the earth or on uprights, giving protection from the elements, especially rain, sun, snow, and wind. A roof is often part of the total building envelope. The roof is made of many different materials. It can be constructed out of wood, metal, concrete, and tile. The most common types of materials are slate, cedar shakes, and clay tiles.
Flat roofs are simple and flat, with no slope to them. Most often these roofs are constructed from wood, though concrete and tile are also used. These roofs need very little maintenance and are ideal for areas that receive little rainfall, such as desert regions. A flat roof also insulates better than a sloped roof, allowing heat to be trapped within the structure during winter and cooling off the inside during the summer.
Different types of roofing materials include clay tiles, composition shingles, slate, asphalt, and other synthetic materials. The composition shingles are made up of chips of clay or rock particles attached together under high pressure. Chimneys and vent pipes usually use composition shingles because they do not permit the water to build up in the crevices between the tiles. Roofing joints are typically made of metals, although they can also be made of plastics.
Roofing materials are separated into two categories, those used for both ventilation and heating and those used only for ventilation. Base flashing, which forms the face of the roofing material, provides the waterproofing and structural integrity of the roof. It seals against moisture and seepage and prevents rain and snow from entering through the edges. Chimney and vent pipes also use flashing, but their role is limited to ventilation.
Old shingles are called shinglepanes and they have a tendency to break or chip if they are exposed to strong winds, rains and snow for a long period of time. Instead of replacing them, old shingles can be repaired by substituting the flat top of each with a weighted bottom that is installed on top of the damaged shingle panes. Panels that are wider at the bottom than they are at the top will give the roofing enough support to avoid cracking. Once these are replaced, all that is needed to continue to keep the roof free of leaks and water accumulation is to attach an electric fan to the underside of each shingle pan to circulate air.
Roofing flashing is typically a polystyrene membrane attached to the bottom surface of each shingle pan, providing thermal and sound insulation. A metal plate is fastened to the flashing, which helps keep it in place and provides additional strength. Flashing is usually installed over asphalt shingles, but it can also be used over tar and gravel roofs, providing greater flexibility for the roof deck contractor. The tar roofs tend to buckle under pressure from heavy winds, while gravel shingles resist tearing.