Should waterproofing underlayment go over or under metal drip edge?

Check the most current guidelines from the NRCA and Building Code.

Check the most current guidelines from the NRCA and Building Code. If ice ever backs up from a clogged gutter, the ice can get under the drip edge and reach the plywood. If the membrane is installed first, the plywood is better protected. Also, if galvanized drip edge ever rusts, it is easier to replace when reroofing if it is installed on top of the membrane.