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

https://tessatopmaid.com/approved-contractor-schemes-do-they-actually-matter-for-guarantees/

Single ply roof guarantees usually cover 15-20 years, but the real service life can stretch well beyond that, often 25-40 years. Guarantees focus on material faults, while actual lifespan depends on maintenance, weather, and installation