How to Fix a Window That Lets in Rain

Rain leaking through a window causes water damage, mold, and structural rot. It needs to be fixed promptly. Here's how to find where the water is getting in and seal it properly.

Why Is Rain Getting Through My Window?

• Failed exterior caulk: The caulk between the window frame and the wall has cracked or shrunk
• Damaged or missing glazing compound: The putty around the glass has cracked (single-pane windows)
• Cracked or damaged frame: The frame itself has cracks that allow water entry
• Failed window seal: The seal between the glass and the frame has deteriorated
• Improper flashing: The metal flashing above the window is missing or damaged
• Window not closing fully: A gap in the closed window allows rain to blow in

Step 1: Find the Entry Point

During or after rain, trace the water back to its source. Water often travels along surfaces before dripping, so the entry point may be higher than where you see the water. Check the exterior caulk lines, the glazing compound, and the frame-to-wall joint.

Step 2: Recaulk the Exterior Frame Joint

This is the most common fix. Remove all old, cracked caulk from the joint between the window frame and the exterior wall. Apply fresh silicone caulk in a continuous bead with no gaps.

• GE Advanced Silicone Caulk Window & Door Clear — 100% waterproof, freeze and sun proof; the right product for exterior window sealing
• Bates Caulking Gun 10:1 No Drip — smooth, controlled bead application
• Caulking Tool 5-in-1 Silicone Removal Kit — remove old caulk cleanly before applying new

Step 3: Repair Glazing Compound

On single-pane windows, cracked glazing compound (the putty around the glass) is a major water entry point. Remove all cracked putty with a putty knife and chisel, then apply fresh glazing compound.

• DAP '33' Window Glazing White 32oz — professional-grade glazing compound; apply, smooth, let cure, then paint over

Step 4: Check and Repair the Flashing

Metal flashing above the window directs water away from the frame. If it's missing, bent, or has gaps, water runs behind the frame and into the wall. This is a more involved repair — the siding may need to be partially removed to access and replace the flashing.

Step 5: Seal Cracks in the Frame

Fill any cracks in the window frame with exterior-grade caulk or wood filler, then prime and paint to protect from further moisture damage.

Step 6: Ensure the Window Closes Fully

A window that doesn't close completely will let in wind-driven rain. Fix any sticking, warping, or latch issues so the window seals tightly when closed.

After the Repair: Check for Mold

If water has been leaking for some time, check the wall around the window for mold or rot. Address any mold immediately with a mold-killing primer before repainting. Structural rot may require professional repair.

Prevention

• Inspect and recaulk all exterior window joints every 5–7 years
• Check glazing compound annually on single-pane windows
• Ensure gutters direct water away from windows
• Paint all wood surfaces to seal against moisture