How to Caulk Windows

Step 1: Remove the Old Caulk
Use a utility knife to score along both edges of the existing caulk bead, then work a putty knife or caulk removal tool underneath it to lift it away. Pull out any remaining pieces with needle-nose pliers. Take your time here - leaving old caulk in place and caulking over it usually leads to early failure.

Step 2: Clean the Surface Thoroughly
Wipe down the joint with isopropyl alcohol or a mild cleaner to remove dirt, oil, dust, and any mold residue. Allow the surface to dry completely. Applying caulk to a damp or dirty surface is one of the most common reasons a new bead fails within a season.

Step 3: Apply Painter's Tape
Run painter's tape along both sides of the joint, leaving the gap exposed. This keeps the lines clean and makes the finished bead look professional. Press the tape edges down firmly so caulk does not bleed underneath.

Step 4: Load the Caulk Gun and Cut the Tip
Insert the caulk tube into the gun. Cut the tip at a slight angle - start with a small opening, around the diameter of a pencil. You can always make it larger, but you cannot undo a tip that is cut too wide.

Step 5: Apply the Caulk Bead
Hold the gun at roughly a 45-degree angle to the joint. Apply steady, even pressure on the trigger while pulling the gun smoothly along the gap in one continuous motion. Try to complete each joint without stopping so the bead stays uniform. Fill the gap fully without overfilling.

Step 6: Smooth and Tool the Bead
Dip your finger in water or use a caulk finishing tool and draw it along the bead in one smooth pass. This presses the caulk into the joint for better adhesion and leaves a clean, concave profile that sheds water effectively.

Step 7: Remove the Tape and Allow to Cure
Pull the painter's tape away slowly at a 45-degree angle while the caulk is still wet. Allow the caulk to cure according to the manufacturer's instructions - typically 24 hours before painting and longer before exposing it to rain. Avoid touching or disturbing the bead during this time.

• Work from a stable ladder when caulking exterior upper-story windows - never lean or overreach
• Wear safety glasses when cutting out old caulk to protect against flying debris
• Read the caulk label for ventilation requirements - some formulas have strong fumes and should not be used in enclosed spaces without airflow
• Check weather before starting exterior work - do not apply caulk if rain is expected within 24 hours or if temperatures are below 40 degrees Fahrenheit, unless the product specifically states otherwise
• Wear gloves when working with silicone caulk, which can be difficult to remove from skin
• Dispose of old caulk and packaging according to local guidelines