No drip edge on your roof? What the code requires and when a retrofit is worth it

The owner posted two threads to r/Roofing on Wednesday, asking whether the missing flashing matters and how to install it on a finished roof. Plenty of houses are in the same spot. Builder Mike Guertin wrote in the Journal of Light Construction that the IRC did not call for drip edge at eaves and rakes until 2012, so jurisdictions still on older codes may not require it at all.

Section R905.2.8.5 now does. The metal must reach at least 2 inches onto the deck, hang at least 1/4 inch below the sheathing, lap 2 inches at joints and be nailed no more than 12 inches apart. Underlayment laps over it at the eaves and runs under it at the rakes. The International Code Council's notes on the 2012 change say the flashing keeps edge shingles from curling and moves water off fascia and rake trim. GAF strongly recommends drip edge at eaves and rakes on all its shingle roofs, and requires eave metal for its Silver Pledge and Golden Pledge warranties.

Without it, the Asphalt Roofing Manufacturers Association says, water that runs back under the shingle edge can rot the deck and fascia. IKO adds that the gap between fascia and deck can let animals in. ARMA's fallback for roofs with no drip edge is a shingle overhang of 3/8 inch to 1 inch at eaves and rakes. That gives owners a first check: measure the overhang, then probe the fascia and the deck edge for soft wood.

A retrofit does not require tearing off shingles. IKO's method uses two people: one lifts the edge shingles while the other pries out nails, slides the metal under and fastens it with nails and roofing cement. IKO says an extended Type F profile suits jobs where new drip edge goes onto an existing roof. Slid in from the edge, the eave metal ends up on top of the old underlayment, the reverse of the order the code sets for new work.