"There are many variables to consider if you are selling a home with an older roof. How old? How bad? Leaking or just likely to leak? You need to consider the age, condition and size of a house in relationship to surrounding houses and whether there is a likelihood of a teardown," said Mary Prochnow of Mary Prochnow Realtors in Los Altos.

An old or leaky roof becomes a factor in trying to decide whether to replace a roof for resale. Realtor Dante Drummond of Coldwell Banker in Palo Alto said there is always the possibility that buyers may want a different kind of roof or consider putting on a second story as an option.

"If the house looks dreadful because of the roof, it might be best to get bids and credit the buyer toward re-roofing. The best time to get roofing bids is when inspections are ordered so that buyers don't expect to reduce the price by three times more than what it may cost to replace the roof," said Drummond.

For those homeowners who are not ready to sell, a good time to think about the condition of the roof is early fall, well before the rainy season.

While a leaking roof is an obvious sign of trouble, the National Roofing Contractors Association advises homeowners not to wait until serious damage occurs before checking out the roof system. If there is cracked paint, discolored plasterboard and peeling wallpaper, these may be indoor signs of a damaged roof. On the outside, cracked, warped or missing shingles; loose seams and deteriorated flashings; loose material or wear around chimneys, pipes and other penetrations; and excessive amounts of shingle granules in the gutters all signal trouble.

Most roof systems last about 20 years, while some roof types—such as slate, clay tile and certain metals—can last longer. The life span of a roof is influenced by several factors: the local climate and environment; material quality and suitability; whether the system was built and designed properly; and whether the roof has received adequate maintenance. Most manufacturers provide warranties, so it is important to check out the fine print to see whether the roof is holding up to the guarantee.

The cost of a new roof also depends on a variety of factors: the materials selected; the location of the home; and the cost for the contractor. The National Roofing Contractors Association recommends getting three or four proposals from reputable contractors in the area to get an idea of the price.

There are different grades of roofing materials with corresponding prices. To determine whether a roofing system fits into the budget, the association recommends using a formula that takes the total cost of materials and labor and divides it by the life expectancy of the roof in years to get the annual roofing cost.

When choosing what kind of roof system to install, cost and durability are usually at the top of the list, but aesthetics and architectural style are also considerations. In light of the recent fire disaster at Santana Row in San Jose, fire-resistant material takes on a new importance. California state law has required fire-resistant roofs since 1995 and requires wood shake roofs to be chemically treated and tested for fire resistance. Fire resistance is measure on a scale from A to C , with A being the most resistant to fire and C being the least resistant. Many older homes have wood shake roofs that are more susceptible to fire than other roofing materials.

Wood shingles and shakes are usually made from cedar, redwood, southern pine or other woods, and their natural look is popular in California. But many wood shingles only have a C fire rating or no rating at all. While there are some Class A fire ratings available for certain wood shingle products, they tend to be costly.

Other choices for roofing materials include asphalt, composition, tile, slate and metal. It's beneficial to view homes with different roofing systems to see what each product looks like. A roofing contractor can explain the differences and the advantages and disadvantages of each system.

Since buying a roof system is such a significant investment, finding a professional roofing contractor is important. All roofing contractors are not alike, and the National Roofing Contractors Association recommends using the following guidelines for selecting a professional.

* Check for a permanent place of business, tax ID number and business license.

* Ask the roofing contractor for proof of insurance and insist on seeing copies of his liability coverage and workers compensation certificates.

* Check to see if the contractor is properly licensed or bonded.

* Look for a company with a proven track record. Call to check client references.

* Get a detailed, written proposal that includes the description of the work and specifications, as well as the starting and completion dates and payment procedures.

* Ask the contractor for a list of the roofing manufacturers for which his company is a licensed or approved applicator.

* Check to see if the contractor is a member of any regional or national industry associations.

* Carefully read and understand any roofing warranties.

* Choose a company committed to worker safety and education.

* Do not necessarily go with the lowest bid.

As the old adage goes, "If it sounds too good to be true, it probably is." Price is not the only criteria for selecting a roofing contractor. Quality workmanship, experience and professionalism should weigh heavily in the decision.

For more information, visit the National Roofing Contractors Association's website at www.nrca.net.