Is a leaking window under a metal roof a window problem or a roof problem?
Short answer. Often it is the roof, not the window: water from a failed endwall or sidewall flashing, a missing kickout, or a loose trim on the metal roof above can run down inside the wall and show up at the window head or sill. Test before you replace anything, starting with the window itself and working up to the roof flashing, because a new window will not stop water coming from above it.
How roof water ends up at a window
- Endwall flashing: where a metal roof meets a wall above a window, failed closures or flashing let water into the wall, and it drains down onto the window head.
- A missing kickout: at the bottom of a sidewall, water runs behind the siding and into the window opening below.
- Rake and eave trims blown loose, sending water against the wall.
- Overflowing gutters above the window, spilling behind the siding.
What a true window leak looks like
- Water appears when rain hits the window directly, not only in storms that load the roof.
- Failed caulk or glazing, a cracked frame, or clogged weep holes in the sill.
- Missing or reversed head flashing above the window.
Test in order
- On a dry day, with someone inside, run a hose gently on the window glass and frame only: sill first, then sides, then head.
- If it stays dry, move up to the wall above the window.
- Then test the roof flashing where the metal roof meets the wall, and the kickout, one area at a time.
- Note which step makes water appear.
What the fix looks like
If the window leaks on its own, a window installer replaces the sealant, flashing tape or unit. If the water comes from above, the fix is roof flashing: new closures and endwall flashing, a kickout, resecured trims, and the housewrap lapped correctly over the flashing, with the wall checked for rot while it is open. Replacing a window without fixing the roof just sends water into the new frame. See roof flashing explained and metal roofing in Georgia.