Make sure it’s insurance-backed
First make sure the guarantee you are getting is insurance-backed. Don’t just accept a roofing company’s guarantee. The minimum period should be 10 years; longer guarantees are available up to 25 years, but the premiums are really expensive.
Don’t fall for this con trick!
Some roofers are selling insurance-backed guarantees as 20 year policies, but these are actually two ten year policies running back to back! They suggest that after the first ten year period runs out they will renew the policy with another 1o year policy, therefore giving a 20 year insurance-backed guarantee.