Commercial reroofing in California involves installing a new roof over an existing one, sans removing old materials. Signs for considering this include aged roofs, weather damage, leaks, high energy bills, or unsightly appearance affecting curb appeal. Benefits encompass extended roof life (up to 20 years), enhanced energy efficiency, reduced maintenance, improved aesthetics, and increased property value. 
Diverse options exist—metal, TPO, EPDM, modified bitumen, BUR—each with pros and cons, dependent on factors like roof size, budget, and energy goals. The process includes inspection, preparation, installation, and cleanup, with costs varying by roof size, system type, and local labor rates. Overall, it's a cost-effective means to enhance roof longevity and performance in California.