What is a Drip Cap?
A drip cap is the metal flashing installed above a window or door, also called head flashing. It tucks behind the siding above the opening and projects forward, directing rainwater out and away so it cannot run down behind the trim and into the wall.
Jim Dodson, HAAG Master Inspector · #992109047 A drip cap, also called head flashing, is a piece of bent metal flashing installed above a window, door, or horizontal trim board. Its profile has a top flange that tucks up behind the siding or weather barrier, a face that covers the top of the trim, and an outer lip that projects forward and kicks down. That shape forces rainwater running down the wall to drip off the front edge instead of running back into the gap above the window. It is one of the simplest and most important pieces of water management on a wall.
What it does
A drip cap manages the water that runs down the face of a wall. Rain sheeting down siding has to get past every window and door in its path. Without a drip cap, that water reaches the top of the window trim and has two options: drip off the front (fine) or wick backward into the joint between the trim and the wall (a slow, hidden disaster). The drip cap removes the second option. Its forward-projecting lip creates a physical break, water cannot defy gravity and curl back uphill, so it drips off the front edge and continues down the face of the window. The top flange, tucked behind the siding and over the weather barrier, ensures any water that does get behind the siding is shed out over the cap, not behind it.
Where it sits
Look at the very top of any window or door. The drip cap sits directly on top of the head casing (the trim board above the opening), running the full width of the trim and usually extending an inch or so past each side. Its top flange disappears up behind the siding and the house wrap. On a correctly built wall, the layering from the top down is: siding, then drip cap top flange, then weather barrier, then the window head. Each layer laps over the one below it so water always travels down and out.
Common problems with drip caps
Missing entirely
Shockingly common, especially on homes where windows were replaced by a window-only contractor who left the flashing to "the siding guy." No drip cap means water runs straight into the joint above the window. The rot shows up years later as soft trim and stained drywall inside.
Caulked instead of flashed
The classic shortcut: skip the metal drip cap and run a bead of caulk along the top of the window trim instead. Caulk is not flashing. It fails within a few years, cracks, and then funnels water into the exact spot the drip cap was supposed to protect.
Top flange installed over the weather barrier instead of behind it
The drip cap top flange must tuck behind the house wrap so the wrap laps over it. Installed on top of the wrap, it creates a reverse lap, a channel that directs water behind the barrier instead of in front of it.
Too short or no end dams
A drip cap that stops flush with the edge of the trim, or has no turned-up ends, lets water run off the sides and straight down behind the casing. Proper drip caps extend past the trim and have small end dams.
How to inspect drip caps on your home
Drip caps are visible from the ground at every window and door. Walk the perimeter and look at the top of each opening. Check for:
- Is there a drip cap at all? Look for a thin metal lip projecting from the top of the window trim. A flat caulk line with no metal means there is no drip cap.
- Caulk along the top of the trim: a bead of caulk where a drip cap should be is a red flag, not a fix.
- Staining or peeling paint on the trim directly below the head: water marks running down from the top corners of a window mean the drip cap is missing or failing.
- Interior signs: stained or soft drywall above an interior window, or peeling paint on the inside head casing, often traces back to a missing exterior drip cap.
Worried about leaks above your windows?
A JDH inspector will check for drip caps and proper head flashing at every window and door, look for stain patterns that point to missing flashing, and tell you whether water is getting into the wall. About 1 in 4 inspections result in no recommended work because we are not paid on commission.