Window Leaking — seal

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

1. Map when and where the water first appears

   Dry the sill and nearby trim, then observe during the next safe rain event from indoors. Record whether water starts at the sash-to-frame seal, glass-to-sash edge, track, lower corners, head trim, side jamb, or wall above the window. If the glass is wet without rain, compare the room-side surface with the space between panes and note the indoor humidity or temperature conditions.

   Expected result: Water begins at a visible seal gap; collects in the track but not on the wall; appears between glazing panes; appears above or beside the frame; or occurs only as room-side condensation.

   Next step: Continue with the matching seal, weep, or opening check. If water reaches finished wall materials, stop repeated testing and arrange an envelope or window assessment before hidden damage spreads.

   Stop if: Stop for water near electrical equipment, ceiling damage, sagging or bulging drywall, visible mold, unsafe exterior access, or a storm condition that makes observation hazardous.

   Why this matters

   Why: The first wet location changes the repair path. A sash or glazing seal points toward a gasket or glass-unit assessment; track water can be a normal drainage event or a blocked weep; water above or beside the frame suggests flashing, cladding, or installation; room-side moisture may be condensation rather than rain leakage.

2. Close and lock the window, then inspect the seal

   Remove only a visible object from the sash or track and close the window normally. Check that the lock engages without force and inspect the weatherstrip or gasket around the sash and frame for cracks, tears, flattening, gaps, missing sections, or a section pulled out of its channel. Do not remove the seal or alter hardware as a generic test.

   Expected result: The window will not close or lock evenly; the weatherstrip is cracked, torn, compressed, missing, or displaced; the seal contacts evenly; or the leak continues despite a secure closure.

   Next step: Follow the exact product instructions for seating a displaced seal or adjusting a permitted user control. If the seal is damaged, order only after identifying the exact window system; if closure is distorted or the leak persists, arrange professional diagnosis.

   Stop if: Stop if the sash binds, the glass or frame is cracked, the lock requires force, the seal cannot be reseated without dismantling, or the window is above a height that makes exterior access unsafe.

   Why this matters

   Why: A lock that does not draw the sash into its seal or a damaged weatherstrip can leave a direct water path. An intact, evenly compressed seal with a continuing leak shifts attention to drainage, glazing, flashing, or the wall opening rather than an immediate gasket replacement.

3. Inspect exterior sealant and the surrounding opening

   From safe ground level, inspect the visible perimeter sealant, trim, flashing edges, siding, and head area for an open joint, cracked or deteriorated sealant, loose covering, or a path that lets water run behind the frame. Do not apply a new bead over a suspected drainage path, and do not seal the bottom of a frame or fill weep openings unless the exact product instructions expressly require it.

   Expected result: The perimeter has a clear gap; sealant is cracked or detached; trim or cladding is loose; water starts above the window; or the exterior looks intact while the interior still gets wet.

   Next step: Photograph the defect and follow the window manufacturer's repair guidance or call a qualified installer. Do not use caulk to hide a recurring leak or to block a drainage route; have the surrounding opening assessed when water travels behind trim.

   Stop if: Stop for loose masonry or cladding, suspected structural movement, deteriorated framing, unsafe ladder or roof access, or any repair that requires removing trim or opening the wall.

   Why this matters

   Why: A gap can admit water, but the visible perimeter is not the whole waterproofing system. Andersen explains that flashing and drainage layers manage water around a window and that sealant alone can trap moisture. An intact exterior with a recurring interior leak may require access to the installation or wall assembly.

4. Check the sill and weep holes for drainage

   Only when the window and surrounding area are dry and safe, locate the manufacturer's exterior weep openings at the lower frame and the corresponding track path. Remove loose visible debris with a soft brush or the product-approved tool; do not drill, enlarge, caulk, or push debris deeper. If the product guidance allows a small water check, add a modest amount to the track and watch from outside for drainage.

   Expected result: Water exits through the exterior weep openings; water remains in the track; an opening is visibly blocked or caulked; there are no identifiable weeps; or water reaches the interior wall despite an open drainage path.

   Next step: Clean only the accessible blockage and retest once. If drainage remains poor, the weeps are sealed, the frame must be dismantled, or water still reaches the wall, stop and arrange product or building-envelope service.

   Stop if: Stop if cleaning requires removing the sash or track, if water could reach electrical equipment, if the opening is above unsafe height, or if the drainage design is unclear.

   Why this matters

   Why: A functioning weep path supports drainage from the track. No exterior discharge or visible blockage can leave water trapped in the frame, while an open path with continuing wall leakage points beyond the seal to flashing, frame joints, or the surrounding wall. Not every window uses the same weep layout.

5. Separate a seal failure from glazing or installation failure

   After the safe external checks, compare the first wet location and recurrence pattern. If water appears at the glass-to-frame edge or between panes, inspect only for visible failed glazing seal symptoms; if it enters around the frame, head, or wall, document the opening and surrounding materials. Do not remove glass, inject sealant into a cavity, or open the wall to chase water yourself.

   Expected result: The leak follows a damaged gasket; moisture is between panes; water appears around the frame or above it; the same wall area is repeatedly wet; or the window remains dry after closure and drainage are corrected.

   Next step: For a confirmed seal or glazing symptom, provide the exact window identification to a qualified repair provider. For frame, wall, roof, or recurring moisture, arrange a building-envelope or original-installer assessment and protect the interior until it is resolved.

   Stop if: Stop immediately for structural rot, mold or sewage-like contamination, damaged glass, an unsafe opening, water near electrical systems, or any need to remove glass or finished wall materials.

   Why this matters

   Why: A replaceable weatherstrip is only one possible seal. A failed insulating-glass edge seal, installation flashing, roof or cladding defect, or concealed wall path needs a different trade or repair method. A dry test after correcting a closure or weep issue supports that limited cause but does not prove the entire assembly is waterproof.