Choosing the right roofing material for your addition often comes down to matching the roofing on the existing house. When you do have to make a choice, the style of roof—pitched or flat—is the first consideration. Materials for a pitched roof include wood shakes and shingles, asphalt shingles, tile, metal, and slate. You can cover a flat roof with tar and gravel, modified bitumen roofing, EPDM rubber roofing, asphalt roll roofing, metal, or PVC membrane. Other factors that will affect your decision include location, climate, style, level of maintenance, and cost. Look at materials from several manufacturers, and compare the features and the warranties they offer.
Wood shakes and shingles are traditional choices for older homes and newer custom homes. Usually made from cedar, wood shakes and shingles are dependable choices if they're high quality and properly installed. Unlike other types of roofing, wood shakes and shingles are usually not rated by fire safety codes, but there are options for protecting against fire. Spray-on fire retardants are available, but they only last a few years. Shakes and shingles that have been pressure-treated with fire retardant are more durable, meet fire safety standards, and provide lasting protection. Wood roofing can last about 30 years.
Asphalt shingles—the most common roofing used in the United States—are made with a fiberglass or organic base that's saturated with asphalt and coated on one side with mineral granules, like small gravel. The mineral coating resists weather damage. Fiberglass-base shingles tend to be more flexible and stronger than organic ones. There are a variety of colors to choose from. You can expect the shingles to last 20-30 years, depending on the quality of craftsmanship. Proper venting and flashing is an important step in the installation process.
Dimensional composition shingles are similar to asphalt shingles, but they're thicker and simulate the look of wood shakes. Depending on the rating, they can last up to 40 years.
Tile roofing is popular for a Southwest- or Spanish-style home. Today the tiles are usually made of concrete and are extremely heavy. Your roof will need to meet specific structural standards, so you should decide on this type of roofing before the roof construction begins. The tiles are available in several shapes. They resist rotting and weather damage, but they may not be ideal for a steep-pitched roof, where they might require additional support. Their life expectancy is long—about 40-50 years.
Metal roofing is ideal for both pitched and flat roofs. It's durable, fire-retardant, and energy-efficient. It's often sold as standing-seam or corrugated panels, but it's also made to resemble other types of roofing, including wood shakes, tiles, and shingles. Metal roofing usually requires little maintenance. In addition to being energy-efficient (it reflects heat, which in turn lowers cooling costs), it's also environmentally friendly, made from 60-65 percent recyclable material. A metal roof can be installed over existing roofing, and you can expect it to last 40 years or more.
Slate creates a striking roof, but that beauty comes with a high price tag. While you pay a lot in the beginning, a slate roof could last 100 years or more. It's stone, so it is fire-resistant. There are different grades of slate, so do some research and shop around to find the highest quality. Like tile, slate is a heavy material and the roof structure must be designed to hold its weight. Slate is available in a variety of colors.
Synthetic slate is not as heavy or expensive as real slate. Some synthetic slates are ceramic products, while others are made of wood fiber. Synthetics aren't as fragile as real slate, but some absorb water, which could cause roof damage if you live in a cold climate with frequent freeze/thaw cycles. Synthetic slate is fire-resistant.
Tar-and-gravel roofs are installed by applying alternating layers of heavy roofing felt and tar. A top coat of gravel protects a flat roof from the elements. The more layers applied, the higher the roof rating. This type of roof is not recommended for wet climates that receive a lot of snow or rain.
Modified bitumen roofing takes a tar-and-gravel roof to the next level, adding a layer of polyester or fiberglass with bitumen for extra strength and durability.
EPDM—ethylene propylene diene monomer—creates a single-layer rubberized roof. It's resistant to ultraviolet (UV) rays and does not require a gravel coating. It's long-lasting but not recommended for wet climates.
Roll roofing is an inexpensive roofing product made of the same type of materials as asphalt shingles. It is a good temporary solution, but you'll probably need to replace the roofing in 8-10 years.
PVC membrane is ideal for wet climates. It has a single layer of material that's welded together with hot air to eliminate any seams that water could pass through. It's UV- and heat-resistant, which will help lower cooling costs if you live in a hot climate.