When replacing a roof, there are two main approaches:
Roof Overlay: Installing a new layer of roofing material over the existing roof. It's less expensive and faster, but not always ideal.
Roof Tear-Off: Completely removing the existing roofing before installing a new one. More labor-intensive but allows for inspection and repairs to the roof deck.
A tear-off is typically preferred, but a roofing contractor can advise on the best approach for your situation.