What size drip edge do you need for a 4/12 pitch roof?
Why 4/12 is a meaningful number
Under the residential code, asphalt shingles are allowed down to 2/12, but slopes from 2/12 up to 4/12 need two layers of underlayment. A 4/12 roof sits right at the line where a single layer is allowed. Because water moves slower and wind can push it uphill more easily at this pitch, many roofers still add self-adhered membrane along the eaves, lapped over the drip edge.
Choosing the profile
- With gutters. A T-style drip edge with a small kick, or a gutter apron with a longer leg that drops into the gutter, keeps the slower sheet of water from running down the fascia behind the gutter.
- Without gutters. A T-style profile with a pronounced kick throws water away from the fascia and siding.
- Rakes. A standard L or T profile matched in color is fine, with underlayment run under it at the rake.
Typical sizes that work
Drip edge comes in 10-foot lengths. A roof flange of 2 to 3 inches suits most 4/12 roofs, and wider flanges give more lap under the membrane. Pick a face long enough to cover the top of your fascia board and extend below the sheathing. Lap pieces at least 2 inches and fasten no more than 12 inches apart, per the code.
What goes wrong at this pitch
The classic failure is a drip edge that stops short of the gutter, so water clings to the underside and soaks the fascia. On Georgia homes that shows up as rotten fascia corners and stained soffits.
See the full detail in drip edge explained, eave membrane in ice and water shield in Georgia, and gutter fit in gutter sizing and seamless gutters.