The life expectancy of your roof depends on several factors; type of roofing, quality of material, and exposure to harsh weather elements among the top. With regular maintenance and normal weathering factors, a roof can last anywhere from 10 100 years.Common roofing material such as built up roofing usually lasts 12 20 years, metal roofing 15 40 years, wood shake or shingles 10 40 years, asphalt shingles 15 20 years, and specialty material like slate up to 100 years under good conditions.Leaks start as small cracks in roofing material that may not be visible; water may collect in an adjacent area. To detect such damage, a close inspection of the roof may be necessary.A certified roofing contractor can be called to avoid further damage to the roof, or personal injury to the homeowner caused by trying to inspect it his or her self. A roof inspection should be performed annually; constant weathering by sun, heat, rain, snow, hail, wind, and cold can cause roofing material to break down. A certified roofing contractor will know what to look for.A roof and soffit system should be properly vented to prevent over-heating and moisture retention, two factors that can cause a roof to break down prematurely.Selecting a Qualified Roofing ContractorA certified, experienced contractor offers various services. From completely tearing off an old roof and replacing it with a new one, to inspecting and certifying an existing roof. The latter is a process in which the roof is inspected and guaranteed to function properly for a certain period of time; usually 2 years. The contractor takes responsibility for any necessary roofing repair during that period.A certified contractor is knowledgeable of roof system types, materials, and installation procedures best suited to each project, and will ensure there is adequate venting.Ask potential roofing contractors questions such as whether or not they are licensed and bonded. What liability insurance coverage they carry, and whether it is up to date. Ask which roofing product manufacturers they are licensed and approved by, for installation of products and warranty purposes. Also ask if they are a member of any regional or national trade organizations.Several resources are available to find a certified roofing contractor; referrals, local government licensing agencies, and web sites that offer contractors for hire, or a list of contractors who are licensed and bonded.