Have you looked up recently? Many homeowners cross the threshold into their homes without giving much thought as to how the dry, warm shelter awaiting them stays dry and warm.

The ubiquitous roof has served humankind well since primitive times. And although wood continues to be a popular roofing material, especially in California, the rustic Northwest, and sections of the Midwest, architects and homeowners have even more materials and shapes from which to choose. Climate, aesthetic appeal, home style, cost, and roof slope (the degree of pitch) factor into what you find over your head.

Roofing materials vary around the country and from state to state, but clearly the most popular choice in home roofing is the asphalt shingle. Asphalt shingles can be reinforced with organic felt or fiberglass. Generally, fiberglass shingles resist fire better than organic shingles. Available in a variety of textures and colors, asphalt stands up well to wind, tears and nail pull and it proves to be the material of choice for complex roofs. This inexpensive and versatile material has a life expectancy of up to 25 years.

Homeowners can select from a range of non-asphalt roofing materials as well. Slate, renowned for its durability, has been used for hundreds of years. However, you will want to consider that slate has the tendency to shatter when hit by objects, such as a golf ball or wind-swept debris. So if you must have a slate roof, extend its service by having a slater inspect it annually for any damage, including missing or cracked slate tiles, flashing wear, and rusted nails.

Another attractive roofing material is clay. Kiln-dried clay tiles come in an assortment of colors, finishes, and shapes—from half-barrel to ribbed to flat. The weight of the clay tiles may require additional framing support. Like slate, they can shatter, and tiles are predisposed to discoloration problems. Although repairs tend to be pricey, a well-maintained tile roof can last 40 or more years.

Concrete is another heavy-duty material requiring additional support. This long-lasting product has a life span of 25-40 years. As with clay tiles, they may become discolored if not treated periodically.

For a lightweight alternative to clay and cement tiles, consider steel. You may save on the cost of adding framing support. As an added benefit, steel tiles are fire retardant and shatterproof.

Shakes and shingles, which top roughly 10 percent of American homes, are made mostly from red cedar in a variety of grades and thicknesses. Shakes, often hand-hewn, are thicker and last longer than shingles, which are machine-sawn and less expensive than shakes. Wood roofing should be treated with a fire retardant. It's best to buy shingles that have been pressure treated at the factory. Because exposure to the elements eventually wears away the chemical, some experts suggest reapplying it annually. A wood shingle roof should last 15-20 years. Plus, you can extend the life of a wood roof by providing proper attic ventilation

What are the signs that a roof needs attention? Major windstorm or hurricane damage leaves no doubt. But normal wear and tear, devoid of acts of god or man, can lead to damage that doesn't always become evident until it's too late. An annual inspection should uncover potential long-term problems. Have an experienced roofer check flashing (the metal sealing the chimney, dormers and vent pipes) for rust and broken seals. In the attic, dark water stains and holes with light escaping may be evidence of deteriorating flashing, the most common cause of leaks. Inside the house, damaged plaster and wallpaper may also indicate flashing damage. Depending on the type of material (asphalt, wood, etc.), roofing also needs to be inspected for missing, cracked, curled and discolored shingles or tiles, rusted nails, warped and split wood, an uneven roof line and holes. On the ground, look around areas near downspouts. As asphalt shingles deteriorate, granules wash off and collect near downspouts. In addition to the annual

inspection, keep the gutters clear of leaves and debris to prevent ice dams (ice begins to melt and back up under the shingles and into the house). Contact a roofer at the first sign of a leak. Left unchecked, leaks can lead to major structural damage and costly repairs.

Depending on the extent of the damage, the roof may require simple repairs or more drastic steps—a tear off, where the old roofing is removed, or a lay over, where new shingles are nailed over existing ones. Many people prefer a lay over because it's less expensive. A tear off requires more demolition and carting, driving up the cost. Check with your contractor or municipality before proceeding. Some building codes limit the number of layers, in many cases to two. Also, you may be required to apply for a permit to make certain roof repairs.

Get at least three estimates then compare prices on the work proposed rather than on the cost. The estimate will include labor, which typically adds 50 percent to the cost of materials. How much you pay for materials generally depends on their weight and the length of the manufacturer's warranty.

When selecting roofing material, have the contractor provide you with three choices—his recommendation, one that's less expensive, and one that's more expensive. Ask to see full-size samples along with manufacturers' brochures. Better still, see if the contractor knows of a home nearby that's topped with the material that interests you.