Single ply roof guarantees usually last 15-20 years, but the real service life...

https://www.4shared.com/office/Q9ZZDzKPge/pdf-27402-44163.html

Single ply roof guarantees usually last 15-20 years, but the real service life can stretch to 25-40 years if the roof’s looked after properly. These guarantees cover materials and workmanship but don’t always account for wear and tear or poor maintenance