Single ply roof guarantees usually cover 15-20 years, but these membranes can...

https://redditchstandard.co.uk/lifestyle/how-long-does-a-single-ply-membrane-roof-really-last-a-building-owners-guide/

Single ply roof guarantees usually cover 15-20 years, but these membranes can last 25-40 years with proper care. The guarantee mainly covers materials, not wear and tear or maintenance issues