Many people don't think about how much work their roof does to protect their home until an issue arises. A well-maintained roof is an important investment, which is why the National Roofing Contractors Association (NCRA) advises homeowners to inspect their roofs each spring and fall.

If you haven't been diligent about inspecting your roof throughout the year, you may notice some signs that your roof is on its last legs, or at the very least needs a little touch-up.

Whether you can get away with just repairs or a partial reroofing versus a full replacement will depend on the types and extent of any issues you discover. Even if you discover any of the common issues below, if your roof was installed properly and isn't over 20 years old, you may not need a full replacement.

• Water stains or mold. Water stains or mold growth on your ceiling are sure signs you've got a leak. If your home has an attic, you should climb up with a flashlight and perform a thorough inspection. Look for water stains or streaks as well as beams of light coming through the ceiling.
• Damaged shingles. Shingles should lie flat against the roof, so if you spot a large number of buckling, curling or cracked shingles, repairs are in order. Inspect the gutters and downspouts for shingle granules. If your roof is losing a lot of granules in rainstorms, it's probably time for a new one.
• Moss overgrowth. Moss and algae thrive in a damp, dark environment, which is why they're frequently found on the shady, north side of a roof. If left to grow unimpeded, thick moss can cause asphalt shingles to lift. This encourages water to collect underneath, leading to more rotting, deterioration and leaking.

It's fairly easy for homeowners to spot leaks, moss and flapping shingles from the ground or by climbing a ladder to the roof's edge. But other types of damage are not so easily detected and require a professional's trained eye.

If your roof is more than 10 years old, protect your investment by having a reputable roofing contractor perform your seasonal inspections. You should receive a detailed report that analyzes the condition of your roof's structure, materials, workmanship and interior. If repairs or a full replacement are necessary, schedule them as soon as possible. The NRCA cautions that a deteriorated roof system only gets worse with time.

Replacing a roof is a big investment and involves many decisions. Be sure the person you're relying on is worth your trust and can get the job done right the first time. The NRCA recommends that you prequalify roofing contractors using the guidelines below.

• Consult your state's Department of Professional Regulation or Licensing Board to ensure the contractor is properly licensed and bonded.
• Request copies of the contractor's liability coverage and workers' compensation certificates.
• Obtain a list of client references and completed projects. Call the references to see if they were satisfied with the work.
• Check with your local Better Business Bureau (BBB) to look for possible complaints filed against the contractor.
• Insist on a detailed, written proposal. Be sure it includes complete descriptions of the work to be performed, including starting and completion dates and payment procedures.
• Carefully read the roofing warranty. Be sure you understand any provisions that would void it.