Single ply roof guarantees usually cover 15-20 years, but the actual roof can...
https://city-wiki.win/index.php/What_Maintenance_Records_Should_I_Keep_for_a_Commercial_Roof%3F
Single ply roof guarantees usually cover 15-20 years, but the actual roof can often last 25-40 years if cared for properly. Guarantees mainly cover material faults, not wear and tear or damage from poor maintenance