Reseal a Drafty / Leaking Window
Category: Exterior ·
Difficulty: Beginner ·
Time: 2.4h ·
Estimated cost: $45
Tools needed
- Caulk gun
- Utility knife
- Putty knife
- Wire brush
- Rags
- Painter's tape
Materials needed
- Exterior siliconized acrylic caulk (white or clear) (2 tube)
- Silicone caulk (clear, for glass-to-frame) (1 tube)
- Foam backer rod (3/8") (10 lin ft)
- Painter's tape (1") (1 roll)
- Window weatherstripping (V-strip) (20 lin ft)
Execution steps
Find the leak
On a windy day, hold a lit incense stick around the window perimeter inside. Smoke wavers where air leaks. Outside, look for cracked or pulled-away caulk.
Duration: 20 min
Remove old caulk
Use the utility knife and putty knife to peel out the failed caulk fully. Brush the joint clean of dust and paint flakes.
Duration: 30 min
Stuff backer rod for wide gaps
Any gap wider than 1/4" gets a foam backer rod pushed in first — caulk alone fails in big gaps.
Duration: 15 min
Tape, caulk, smooth
Run painter's tape along both sides of the joint. Run a steady, smooth bead of exterior caulk. Smooth with a damp finger or putty knife. Pull tape immediately while caulk is wet.
Duration: 45 min
Add interior weatherstripping
For drafty operable windows, peel-and-stick V-strip into the sash channel where the moving sash meets the frame.
Duration: 30 min
Cure
Don't wash window for 24 hours. Avoid running water on the bead for 48 hours.
Duration: 5 min
Safety first
- Working outside on a ladder — only on calm days, never in rain.
- Don't use silicone caulk on bare wood — it can't be painted over.
- Acrylic caulk is for paintable surfaces, silicone for glass/metal.
When to hire a pro
Foggy double-pane glass, rotted sills, or windows that won't latch are signs of failed seals or rot — get a window pro.
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