Which side of the inner seal is wet?

Photograph the sill before drying it. Identify whether water sits in an outer track, behind the closed sash, on the room-side sill or in the wall finish below. Those locations are not equivalent. A small collection area built into the frame may be doing its job; a puddle on timber trim or flooring should not be dismissed as normal drainage.

Andersen's care document explains that some products collect water in the sill during heavy rain and discharge it through exterior weep holes; drainage may not be immediate Andersen: Product care and maintenance.

Find the window series and its care guide. The slots visible from outside may have covers or baffles that belong there. Do not remove parts just because they look like an obstruction, and do not drill additional holes in a frame to create a route you cannot trace.

The track needs a route to the outside

Water enters the collection track

Window track drains to an exterior weep outletA schematic window sill cross section shows water entering the track, passing through a drainage channel and leaving an exterior opening on the right.Room sideOutsideTrackWeep outlet

Some window frames collect rain in a track before draining it outside. An outlet is part of that system, not automatically a hole to caulk.

Check the exterior outlet

Exterior window sill with open drainage slotsAn outside view shows two drainage slots at the lower window frame with water arrows pointing down and away.Keep intended outlets clear

Dirt or sealant at the outlet can obstruct drainage. Water reaching the room or wall still needs investigation; a clear hole is only one check.

Drainage concept only. Channels and outlet positions vary by window. Identify the manufacturer's intended openings before cleaning or sealing. PNNL window drainage guide.

Distinguish collection from escape into the room

  • Water in designated outer channel

    Observe whether it drains according to the product design.

  • Persistent pooling

    Inspect accessible weep openings and seek the model's cleaning guidance.

  • Water over the inner edge

    Document overflow and arrange an installation or product assessment.

  • Wet trim with a dry track

    Investigate another route around or above the frame.

Clear debris, not the drainage details

Remove loose debris from accessible channels using the manufacturer's method. Avoid pushing a hard wire deep into an opening: internal seals or baffles may be in its path. Do not fill weep slots with caulk to stop a draft. If insects or air movement are concerns, identify the proper cover or component rather than closing the drainage outlet.

Record whether leaves, paint, old sealant or construction dust were obstructing an opening. If the problem began after exterior painting or siding work, that history is useful. Clean only what can be reached safely and leave elevated exterior access to someone equipped for it.

Overflow can have more than one cause

A blocked outlet is one possibility, but sash alignment, displaced weatherstrip, frame distortion or water arriving through surrounding wall details can also matter. Check whether the window closes and locks evenly. A sill that stays wet after cleaning needs more diagnosis, not progressively larger drain holes.

Keep notes on wind direction and the first wet location during the next rain. A controlled water test can help an experienced installer isolate a route, but spraying the entire opening with a pressure washer obscures that sequence. Ask the assessor to explain whether the repair concerns maintenance, a product component or the connection between window and wall.

A clean channel still needs a rain check

After cleaning or service, check operation and observe drainage during representative rain. Dry and inspect any affected indoor finishes; persistent staining or soft material deserves follow-up. If moisture appears within the sealed glass rather than in the sill, use the between-pane fog guide. If the frame is beyond repair, compare replacement methods with the water-management problem explicitly included in the scope.