Step 1
Remove any loose dirt or debris from the seams of the window frame to prepare it for sealing. The caulk will only adhere properly to a surface that is free of contaminants that might trap air in the sealant.
Step 2
Use a pair of sharp scissors or a utility knife to cut a small bit of the nozzle on a tube of butyl caulk. This rubber-based sealant can withstand the most adverse weather conditions and is ideal for use on outdoor applications.
Step 3
Puncture the seal on the tip with a construction nail or stiff wire. Load the tube into a caulking gun.
Step 4
Apply a bead of the butyl caulk to an exposed joint in the window, between the frame and the vinyl siding. Draw the gun along the length of the seam, maintaining steady pressure on the trigger.
Step 5
Repeat the same procedure for each side of the window frame. Butyl caulk should never be smoothed. It is the most adhesive caulking option and will stick to virtually any applicator. Instead, allow it to cure for a few days as is.