In Chicago,  roofing usually lasts 10-20 years depending on the type of roofing used, though with the proper maintenance it can last several years longer. Eventually, however, you will have to replace your roof. Here are some signs that it's time for replacement:

Missing Granules. While it is not unusual for some granules to fall off the shingles, excessive granule loss is an indication that it's time for a new roof. If asphalt or fiberglass peek through the gritty surface, it's time to contact a qualified roofing contractor. Rotting. Rotting is common when the organic material of the forming the core of your shingles begins to absorb moisture. When you repair or replace your roof, use shingles manufactured from non-organic compounds that resist moisture.

Buckling. Buckling can occur for a number of reasons; poor ventilation, wrinkled underlaying, double-layered shingles, and improperly applied felt can all cause your shingles to buckle. If left untreated, the shingles will begin to crack and tear causing significant damage to the roof deck.

Ceiling Spots. Wet spots or brown-ringed stains on your celing, this is probably the result of a leaking roof. Check the attic for the source of the leak, examining carefully since some leaks travel some distance from the actual source. Outside, check the chimney and other penetration points for cracks in the flashing and check for ice dams near the eaves that may cause the water puddle up. Finding the source of the leak is crucial to avoid the growth of black mold which poses a health risk to your and your family.

If you notice any of these problems, your roof could need to be replaced and you should contact a reputable Chicago roofing contractor. Make sure their work is guaranteed and ask for warranty information during your consultation.