Window sill slopes inward: drainage problem or framing damage?
Discussion options
I’m trying to diagnose a window sill that slopes toward the interior by roughly 1/4 inch across its depth. That seems opposite of the exterior drainage pitch I’d expect.
Could an inward slope come from incorrect shimming during an insert installation, settlement, or damaged framing beneath the sill? Before removing trim, what checks would be useful? I’m thinking of checking whether the jambs are plumb, measuring the opening diagonally, looking for staining at the inside corners, and probing any exposed wood for softness.
If the window itself is otherwise sound, can this sometimes be a localized sill or rough-opening repair? Or does an inward pitch usually mean the exterior flashing and sill pan need to be redone? I want to avoid “fixing” the visible slope in a way that traps water against the frame.
Join the conversation
Share your experience or ask a follow-up question.