How many 10-foot pieces of drip edge do you need?
Short answer. Drip edge is sold in 10-foot lengths, and because code calls for adjacent pieces to overlap at least 2 inches, each piece effectively covers about 9 feet 10 inches. To count pieces, add up the linear feet of every eave and rake, divide by about 9.8, round up, and add a piece or two for corners and cuts.
Measure the edges
- Eaves: the level edges where gutters hang. Measure along the fascia.
- Rakes: the sloped edges on gable ends. Because they follow the pitch, they are longer than the horizontal width of the gable; multiply the horizontal run by the pitch factor, or measure the edge directly.
A roof measurement report usually lists total eave and rake lengths.
Count the pieces
- Add eave and rake lengths.
- Divide by 9.8 to allow for the 2-inch laps.
- Round up and add one or two pieces for corners, cuts and mistakes.
Example: 120 feet of eaves plus 90 feet of rakes is 210 feet. Divided by 9.8 that is about 21.4, so plan on 22 pieces plus 2 spares.
Installation notes that affect the count
- Laps run at least 2 inches, with the upper piece lapping over the lower on rakes so water flows over the joint.
- Corners are notched and folded or cut and lapped, which uses extra material.
- Code calls for fasteners no more than 12 inches apart.
- Underlayment goes over the drip edge at the eaves and under it at the rakes.
Choosing the piece
Drip edge comes in aluminum or galvanized steel, in several profiles and colors. Pick a profile with a flange of at least 2 inches onto the deck and a face tall enough to cover the deck edge, and match the color to the fascia or gutters. For the bigger picture, see drip edge explained and how roofers measure a roof.