What is a drip edge in construction?
The principle behind it
Water sticks to surfaces. A sheet of rain flowing off a roof edge will curl back around the edge and run along the underside if nothing stops it. That is how fascia boards, deck edges and window heads rot. A drip edge creates a sharp break, often with a kick angled outward, so the water lets go and falls straight down.
Where builders use it
- Roof edges. Metal drip edge covers the edge of the roof deck and the top of the fascia. It supports the first course of shingles and keeps water off the wood.
- Above windows and doors. A drip cap or head flashing sends water out over the trim instead of behind it.
- Siding and trim. Z-flashing between siding courses and a water table at the base of walls work the same way.
- Sills and copings. A groove cut under a window sill or wall cap, called a drip kerf, does it without any metal at all.
On roofs, it is code
The International Residential Code, which Georgia enforces in its 2024 edition with state amendments since January 1, 2026, requires drip edge at the eaves and rakes of shingle roofs. It must reach at least 2 inches onto the deck and 1/4 inch below the sheathing, with underlayment lapped over it at eaves and under it at rakes. Many older Georgia homes were roofed before the requirement and have none.
For the roof version in detail, read drip edge explained, and for its cousins, roof flashing explained.