Many people don't think about the roof over their heads until it begins leaking. Do not wait until rain pours through the ceiling for a roof replacement. So how do you know when you should prepare for a new roof installation? Roofs have about 20 years warranty after which it will need replacement. Also, when you see shingles edges curling or shingles falling apart. If the roof is covered with moss or you can see sunlight from your attic are also signs that your roof is susceptible to leaks and you would need replacement.