Water / Article 35

Window Leak and Wall Stains: Is It Rain, Condensation, or Flashing?

Window stains can come from exterior leaks or indoor condensation.

Situation snapshot

The problem in plain English.

Window stains can come from exterior leaks or indoor condensation.

Start with safety and source control. Then work through what can dry, what needs removal, what should be documented, and where professional mitigation or remediation should take over.

Action order

Move through it in the right sequence.

  1. 01Note whether water appears during rain or humidity changes.
  2. 02Inspect caulk, flashing, sill slope, and interior condensation.
  3. 03Dry wall cavities before cosmetic repair.
  4. 04Improve drainage or insulation as needed.

Risk check

What changes the seriousness.

Watch for

Soft drywall, recurring mold, swollen sill, or water inside the wall.

What the pros look for

Pros check moisture patterns and exterior water entry points before repairs.

Source backed

References used for this article.