by Don Vandervort, © HomeTips
Roofs take quite a beating. Fully faced toward the sky, they catch the brunt of weather’s worst. They have to be able to take a licking and keep from leaking for a long time. They must be weathertight, secure, durable, attractive, and elastic enough to withstand severe temperature shifts without cracking.
Over the centuries, roof-building techniques have been refined to yield roofs of considerable strength and durability. A wide variety of materials has been developed that will last many years—in some cases as long as the house. Homeowners have a vast selection of materials, colors, and prices from which to choose.
A contemporary roof, regardless of shape, consists of a variety of components: wood framing, sheathing, underlayment, flashing, gutters, and, of course, the finished surface. The illustrations show how these materials go together to make a sound roof.
The roof’s deck is made up of sheathing and, in most cases, underlayment, which is called roofing felt. The type of deck used depends on the finished roof material. Most call for solid plywood or oriented-strand-board (OSB) panel sheathing; wood shingles and some tile or metal roofs call for spaced board sheathing. Roofing felt is sandwiched between the sheathing and the surface material on most roofs. This heavy, fibrous black paper saturated with asphalt helps repel any water that might find its way past the roofing material.
Flashing helps repel water wherever the roof surface is broken by dormers, intersecting roof planes, protrusions, and along the roof’s edges. Flashing is made from galvanized steel, aluminum, or vinyl.
The roof’s surface is composed of any of several materials. The most popular include:
Wood shingles, which require open sheathing—1-by-6 boards that are spaced apart. The spaces allow air to circulate around the shingles to prevent moisture buildup beneath the wood.
Wood shakes with deeply grooved textures that allow air circulation may be applied over solid sheathing with interlays of 30-pound roofing felt.
Tile and slate roofing is very heavy, sometimes requiring structural reinforcement. Most tile roofs go over solid sheathing and a 30-pound or heavier roofing felt. They’re often hooked onto battens—strips of wood that run horizontally across the roof.
A built-up roof is made from fiberglass-based asphalt sheeting applied in layers with mopped-on hot bitumen between each. The surface is coated with bitumen and a layer of gravel or crushed rock to minimize damage from the sun and abrasion. Newer flat roofs may have layers of single-ply bitumen or rubber-like materials between the asphalt sheeting.
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