Roofing Info from Bob Villa
Whether you are building from scratch or choosing a new roof for your existing home, a wide range of materials are readily available and worthy of consideration. These include asphalt, wood, and composite shingles, as well as slate, concrete, and clay tiles. Style is an important factor, but it’s not the only one. Product cost, material weight, and installation requirements should also influence your selection. Here’s what you need to know:
Before we talk materials, let’s talk terminology. Roofers don’t usually use the measure “square feet.” Instead, they talk in squares. A square is their basic unit of measurement—one square is 100 square feet in area, the equivalent of a 10-foot by 10-foot square. The roof of a typical two-story, 2,000-square-foot house with a gable roof will consist of less than 1,500 square feet of roofing area, or about fifteen squares.
A number of considerations will affect the cost of a new roof. The price of the material is the starting point, but other factors also must be considered. One is the condition of the existing roof if you are remodeling a house—if old materials must be stripped off, and if the supporting structure needs repair, that will all cost money. The shape of the roof is another contributing factor. A gable roof with few or no breaks in its planes (like chimneys, vent pipes, or dormers) makes for a simple roofing job. A house with multiple chimneys, intersecting rooflines (the points of intersection are called valleys), turrets, skylights, or other elements will cost significantly more to roof.
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Not every roofing material can be used on every roof. A flat roof or one with a low slope may demand a surface different from one with a steeper pitch. Materials like slate and tile are very heavy, so the structure of many homes is inadequate to carry the load. Consider the following options, then talk with your designer and get estimates for the job.
Slate. Slate is among the most durable of all roofing materials. Not all slate is the same—some comes from quarries in Vermont, some from Pennsylvania and other states—but the best of it will outlast the fasteners that hold it in place. Hundred-year-old slate, in fact, is often recycled for reinstallation, with the expectation it will last another century. But slate is expensive—typically prices start at about $800 a square—and very heavy.
Asphalt Shingle. This is the most commonly used of all roof materials, probably because it’s the least expensive and requires a minimum of skill to install. It’s made of a fiberglass medium that’s been impregnated with asphalt and then given a surface of sand-like granules. Two basic configurations are sold: the standard single-thickness variety and thicker, laminated products. The standard type costs roughly half as much, but laminated shingles have an appealing textured appearance and last roughly half as long (typically 25 years or more, versus 15 years plus). Prices begin at about $50 a square, but depending upon the type of shingle chosen and the installation, can cost many times that.
Wood. Wood was the main choice for centuries, and it’s still a good option, though in some areas fire codes forbid its use. Usually made of cedar, redwood, or southern pine, shingles are sawn or split. They have a life expectancy in the 25-year range (like asphalt shingles) but cost an average of twice as much.
Metal. Aluminum, steel, copper, copper-and-asphalt, and lead are all durable—and expensive—roofing surfaces. Lead and the copper/asphalt varieties are typically installed as shingles, but others are manufactured for seamed roofs consisting of vertical lengths of metal that are joined with solder. These roofs start at about $250 per square but often cost two or three times that.
Tile and Cement. The half cylinders of tile roofing are common on Spanish Colonial and Mission styles; cement and some metal roofs imitate tile’s wavy effect. All are expensive, very durable, and tend to be very heavy.
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Making the Choice
More often than not, if you are remodeling, the existing roof of your house will determine your choice of roofing material. Should you be considering other options, you’ll want to consider not only the cost but the color, texture, weight, and durability of your alternatives, as well as what traditionally has been used on houses like yours.
Whatever your choice of roofing surface, you will probably need flashing. Flashing is a crucial part of all exterior work, both on the roof and siding. Flashing is metal (aluminum or copper, occasionally lead) or plastic film. It is applied in strips to areas where dissimilar materials adjoin, such as the intersection of the masonry chimney and the roofing shingles, where the siding abuts the window frames, and so on. Good flashing work is essential to keeping a structure watertight, as the most likely place for leakage to occur is where different materials meet.
Whatever the choice of roof materials, the coursing should be regular to the eye and parallel toroof edges. From one course to the next, the joints should be staggered to prevent leakage. Beware of a contractor who relies on tar for joints. Except with certain roofs where a membrane is used, tar is a lazy expedient that should not be used for a new roofing surface.
For most roofing, a material like building felt (a.k.a. tar paper) is rolled on before the shingles are nailed in place. With cedar shakes, however, lengths of furring strips (sometimes called “cedar breathers”) will be laid across the roof in order to allow the roof to breathe. In snowy areas, a membrane called a snow and ice shield may also be laid.