How to Reseal Windows

Step 1: Assess the Seal Type
Before reaching for caulk, identify what needs resealing. Exterior caulk around the frame, interior caulk at the trim, or weatherstripping along the sash are all DIY-friendly. A fogged or moisture-filled insulated glass unit is not - that requires professional glass replacement.

Step 2: Remove All Old Caulk
Using a utility knife, score along both edges of the existing caulk bead. Work a caulk removal tool or stiff putty knife under the strip and peel it away. Be thorough - new caulk will not bond properly over old, degraded material. Remove as much as possible without gouging the frame or surrounding trim.

Step 3: Clean and Dry the Surface
Brush away any dust, mold, or loose debris with a stiff brush. Wipe the joint down with rubbing alcohol or an appropriate cleaner and allow it to dry completely. Moisture trapped under new caulk is one of the most common reasons a fresh seal fails prematurely.

Step 4: Tape Off the Work Area
Apply painter's tape on both sides of the joint to keep lines neat and protect the frame and siding. This step makes cleanup much faster and gives a cleaner finished bead.

Step 5: Apply the New Caulk
Load the caulk tube into the gun, cut the tip at a slight angle to roughly match the joint width, and apply steady, even pressure as you run a continuous bead along the joint. Work in one direction and try not to stop mid-run. For silicone caulk, lightly mist the surface with water before tooling.

Step 6: Tool and Smooth the Bead
With a wet finger or a caulk smoothing tool, press the bead gently into the joint and draw along it in one pass. This forces the caulk into the gap and creates a clean, slightly concave profile that sheds water rather than collecting it.

Step 7: Remove Tape and Allow to Cure
Pull the painter's tape away while the caulk is still wet, pulling at a low angle to avoid lifting the bead. Check the product label for full cure time before exposing the joint to rain - this typically ranges from a few hours to twenty-four hours depending on the product.

Step 8: Replace Weatherstripping if Needed
If drafts persist after caulking, inspect the weatherstripping on the sash. Pull away any old compressed or torn material. Measure the channel length, cut new weatherstripping to fit, and press the adhesive-backed strip firmly into place. Test the sash a few times to confirm a snug fit without binding.

• Work from a stable ladder on a dry day - never lean out of an upper-story window to reach exterior joints
• Wear safety glasses when cutting old caulk to protect against debris
• Use gloves when handling silicone products, which can be difficult to remove from skin
• Ensure good ventilation if working indoors with solvent-based caulk removers
• On older homes built before 1978, disturbing painted surfaces around the frame may involve lead paint - consult an EPA Lead-Safe Certified firm before proceeding
• Do not caulk the weep holes at the bottom of window frames - these are designed to drain water and must remain open