A 10-minute hose test before siding goes on can catch window leaks, Matt Risinger shows

In the video, one person runs a hose over the window from outside while a second person, with a timer and a flashlight, watches the interior side of the opening for water getting past the frame or the flashing tape. The value is in the timing: a leak found at this stage can be traced to a specific lap or corner and patched before siding, trim and drywall hide it.

The test matches published installation guidance for flanged windows. A guide published in August by Building and Construction (build-construct.com) says a flashed window should be water-tested before the siding covers it: wet the opening from the outside, beginning at the bottom and moving upward, then look for drips on the inside. The same guide lists what should already be in place. The sill pan slopes to the exterior and turns up the jambs 4 to 6 inches, a raised back dam on the inside edge keeps water from running past the sill, the tape on the sides overlaps the pan and never tucks under it, and the flashing at the head runs beyond both sides of the opening.

Most leaks in the field begin where tape ends too soon, at a cut corner or at laps installed in the wrong order, the guide says. The glass itself is rarely the source. Keep a short record for each opening: the window number, how long it was sprayed, where water showed up and what was repaired, with photos taken before the cladding crew arrives.