How To Replace Interior Window Sill And Trim. The first step for how to replace an interior window sill is using your utility knife to cut the caulk between the window sill and the trim. Use a utility knife and a hammer if necessary to carefully break and remove any.
Step 1 Pry off the old trim with a pry bar. Away from the jamb at both ends and along the base of the window casing. The second reason to replace window trim is if it no longer fits with the style of the windows and your home.
First we ran a cutting blade This is my favorite caulk removing tool.
Caulk all seams corners and edges. Around all the edges including between the underneath trim and the window sill. If you plan to do a lot of DIY its definitely worth the investment. Nail the thick part of the trim to the framing with 2-in.