Look for: shingles that are lifting up, cracked or missing, with curled edges, or with smooth dark areas, which indicate that the protective granules have worn off.
In Florida’s climate, most asphalt shingles last 15-20 years before needing replacement.
Stains on shingles are typically from algae growing on the shingles, a common problem in Florida’s humid climate. Always follow the shingle manufacturer’s guidelines for cleaning. You also want to avoid damaging the shingles with pressure spray from a garden hose or pressure washer.
There are several reasons why we always remove the existing layer(s) when installing a new roof: The weight of the added materials can be an issue; the roofers are not able to inspect the wood deck supporting the shingles for any damage or rot; and, it may void your warranty on your new shingles if installed on the existing roof.
Confirm they are licensed or have any complaints filed against them with the State of Florida at My Florida Licence.