The most obvious sign of a need to change your roof is that you see a leak. This may come in the form of discoloration of your interior walls/ceiling or a leak in your attic.
Curling shingles or shingles collecting on the ground after a windy day are a signal.
When shingle granules are visible around the shingles and in the gutters, it is time to replace.
When you see dips or buckles in your roof decking, a new roof is needed. This can be easily seen simply by looking at your roof from the ground. This is a sign that a leak exists, and the water has warped the decking.
Sometimes the desire for a cosmetic upgrade drives a homeowner to replace a roof. A change from one type of shingle to another can greatly enhance the beauty of your home, and increase the value of your property, particularly when you are selling your home.