width=312From asphalt to slate: A quick primer on roof coverings. 

The shape and pitch of a roof are important clues to a home's architectural style. But just as important is the material used to build it. 

Roofing materials can lend to a home's character, of course, but they also can help dictate how long the roof will last and how expensive it is to maintain, says Stephen L. Patterson, president and director of engineering for Roof Technical Services Inc. in Fort Worth, Texas, and author of Roofing Design and Practices (University of Texas at Arlington, 2007).

For that reason, when helping buyers evaluate homes-and when marketing properties-the roof material and its condition should be part of the conversation. You should always refer the buyer or seller to a roofing expert for an analysis or necessary repairs, Patterson says. Here's a look at the pros and cons of eight roofing materials:

Asphalt or composite shingles. The most widely used choice, shingles meld with almost any style of house and can be installed by most contractors. The lower-end three-tab shingles last 15-20 years, while heavier and costlier architectural shingles with a three-dimensional look can survive 40 years. But it may be hard to find replacement shingles that match perfectly with older faded ones. Also, less expensive choices may devalue a high-end home.

Clay tiles and concrete. Stylish and more unusual than asphalt, these choices-particularly tiles-look best on certain styles of homes, such as Spanish or Mediterranean, and are found more often in warm-weather regions (clay heats up slowly so it can have a moderating effect on hot temperatures). Tiles are lighter-weight than concrete, but tend to be more fragile. These materials may last 50 to 100 years. They're more expensive than asphalt, take longer to install, and require a seasoned contractor.

Metal. A unique choice that can look modern or ruggedly farmhouse-chic, metal roofs come in many colors and weather handsomely. They're often manufactured in shapes, from shingles to panels, and in various thicknesses and textures-some even resembling dragon scales. On the downside: Metal can be noisy when it rains unless a sound-abatement material is installed. It's also among the more expensive choices, with copper at the upper reaches. A life span of 50 to 100 years is typical.

Synthetic. Many new polymer products have come on the market in recent years, promoted for their durability, light weight, and fire resistance. Composite products can resemble a range of roofing materials, from slate to cedar shake. Even though they're not the real thing, high-quality synthetics are still on the pricey side. Also, many haven't been around long enough to stand the test of time.

Slate. Among the most expensive choices, slate demands a time-consuming installation process. Yet its natural gradations in color and texture make it tough to beat aesthetically, and it's de rigueur on some of the best built high-end homes. It can last 50-plus years.

Planted green materials. Used more today in commercial than in residential properties, planted roofs offer ecological promise. They work best on flat roofs, can be expensive to install and maintain, and are heavy once all the plants and dirt are in place. An engineer should check for a quality waterproof membrane and make sure that the roof can withstand the greenery's weight.

Wood shakes and shingles. These natural materials look terrific on most homes, whether traditional or contemporary. On the plus side: They can last up to 50 years. But they must be treated to withstand fire, and some state building codes don't permit them. Also, they can be pricey-as much as the best slate.

Solar shingles. Dow Chemical Co. will soon release the PowerHouse Solar Shingle, which can be incorporated into home roofing systems along with standard asphalt shingles. The product will cost less than solar panels and be easier to install.