Why Your Window is Leaking: Riverbedding, Weep Holes, and Caulking
Too Long; Didn't Read
- The Panic Moment: Water on the sill doesn't always mean a new window.
- Scenario A (The Easy Fix): Blocked weep holes. Poke them with a wire.
- Scenario B (The Maintenance): Cracked exterior caulking. Cut it out and recaulk.
- Scenario C (The Death Sentence): "Riverbedding" inside the glass. The unit is dead.
Answer First: If you see water on your sill after rain, check the Weep Holes (slits on the bottom exterior frame) first. They might be clogged. If you see "grooves" of moisture looking like a canyon inside the glass panes, that is Riverbedding. It means the seal has failed completely, and the insulated glass unit must be replaced.
A puddle on your windowsill is never good. But before you order a $2,000 replacement, manage the diagnostics yourself.
In my 15 years fixing Toronto windows, 80% of "leaks" are maintenance issues you can fix for $20.
Here is the diagnosis guide.
1. The "Weep Hole" Blockage (Most Common)
Modern vinyl windows are active drainage systems, not submarines.
- The Component: Small rectangular slits on the bottom outside edge of the frame.
- The Problem: They clog with spiderwebs and dust. When track water can't exit, it overflows inside.
- The Fix: Poke a stiff wire (coat hanger) into the holes to clear the blockage. Test by pouring water in the track.
2. Caulking Failure (The Exterior Seal)
Toronto's freeze-thaw cycle destroys caulking.
- The Problem: The sealant between frame and brick cracks. Driving rain pushes water behind the frame.
- The Check: Inspect the perimeter seal outside. Is it cracked or missing?
- The Fix: Scrape out the old caulk (never caulk over it!) and apply high-grade exterior silicone (like Mulco Supra).
3. Riverbedding (The "Game Over" Sign)
This is specific to the glass unit (IGU).
- The Look: Tiny canyons or riverbeds running down the inside surfaces of the glass. You cannot wipe it off.
- The Cause: Seal failure. Silica desiccant dissolved in moisture and etched the glass.
- The Fix: No fix. The thermal seal is gone. You need "Glass-Only Replacement" (we replace the glass unit, but keep your frames).
When to Call a Pro
- Water from the TOP: Likely a roof or siding leak, not the window.
- Soft wall below window: Rot inside the studs. Call a contractor immediately.
- Riverbedding: Call us for a glass replacement quote.
Don't let a $5 tube of caulk turn into a $5,000 mold remediation bill. Inspect your windows every Autumn.