Why Is My Exterior Door Leaking? Check the Threshold, Weatherstrip, and Sill Flashing

Use only checks that match the exact appliance or system and its official guide.

1. Check 1

   During or immediately after rain, observe from inside without removing trim and mark the first place water appears: under the threshold, at a jamb corner, across the head, or on the wall beside the frame.

   Expected result: Water begins at the bottom edge, at one frame joint, above the door, or on the adjacent wall rather than at the door itself.

   Next step: Photograph the first wet point and the area above it, then use that location to guide a professional inspection instead of sealing only the visible drip.

   Why this matters

   Why: A bottom-edge entry makes the threshold, sweep, sill pan, or sill drainage path more likely; a jamb, head, or adjacent-wall entry makes the opening flashing, rough-opening seal, cladding, or an upstream wall detail more likely.

2. Check 2

   With the door closed and latched normally, inspect the perimeter from the interior and exterior for daylight, a loose-fitting edge, a crushed or split weatherstrip, a damaged sweep, or a threshold gap; do not force the door against a seal.

   Expected result: The closed door has a visible perimeter gap or the weatherstrip and sweep do not contact evenly, or the seal contacts evenly with no visible gap.

   Next step: If the door binds or cannot latch smoothly, stop adjustment and call a qualified installer; otherwise document the gap and ask whether the weatherstrip or sweep is the correct repair before applying sealant.

   Why this matters

   Why: An uneven contact pattern can allow air and wind-driven water through the door perimeter and may call for weatherstrip, sweep, hinge, strike, or fit adjustment; an even perimeter does not rule out a concealed sill or wall-flashing leak.

3. Check 3

   From the ground, inspect the exterior threshold, frame corners, trim, siding joints, and any overhang or porch above the door for open joints, damaged trim, water marks, or a path that could carry water toward the opening.

   Expected result: The exterior surface has an open joint, damaged trim, water staining above or beside the frame, or no visible exterior defect.

   Next step: Do not cover an open drainage path with an unverified bead of caulk; photograph the detail and have a qualified professional trace the water-management layers.

   Why this matters

   Why: An upstream wall or trim defect can feed water to the opening even when the door seal looks sound; no visible defect means the sill pan, rough opening, or another concealed layer remains possible.

4. Check 4

   Ask a qualified door installer or building-envelope professional to inspect the sill pan, back dam, jamb and head flashing, rough-opening seal, and the wall below the opening if moisture has reached trim or framing.

   Expected result: The inspection finds a worn perimeter seal only, or finds missing or damaged sill flashing, reverse-lapped layers, an unsealed rough-opening gap, trapped moisture, or deteriorated framing.

   Next step: Request a written scope that identifies the failed layer and preserves outward drainage; do not order a generic sill pan or foam solely from the visible symptom.

   Why this matters

   Why: A perimeter-seal-only result may support a weatherstrip or sweep repair; a flashing, drainage, or framing defect requires opening-specific repair so water is directed outside rather than into the wall.