The best way to extend the life of your outdoor furniture is by cleaning it regularly and not leaving it outdoors unprotected more than necessary.
Clean: With a mild soapy solution.
Maintenance: Require no maintenance.
Storing: If possible, store in a cool dry place indoors. If the furniture is stored outside, cover it with a waterproof cover. After a rain or snowfall, wipe off excess water or snow from flat surfaces. Allow air to circulate to avoid condensation.
