When dealing with roofing and roofing systems, it’s important to differentiate the warranties involved. The asphalt shingles used in your project will come with a manufacturer’s warranty that covers any and all defects in the product due to a manufacturing defect. Usually, these warranties are for the lifetime of the product, or at least a period of 20 years or more. Your contractor should give you a certificate upon completion that details this warranty. They will also offer their own warranty that covers their work on your project. This warranty can be for whatever term they choose, but most are normally at least one year from the date of completion.