How To Put Up Interior Window Trim. One of the easiest and simplest window trim details is a simple flat stock trim. Cut a 45-degree angle on one end of the trim and hold it so the short end of the angle overhangs halfway or 38 in onto the jamb.
Step 2 - Measure. When installing window molding start at the top. Measure the opening of the window to determine the amount of wood needed.
There are two methods of installing interior window trim.
Mark and crosscut the head casing to length. If there are any nails left in the window frame you will need to use pliers or a hammer to pull them out. Ours is 28 inches wide Then decide how wide you want your window sill to come out. Prepare Stool the Piece Lying Flat in the Window Sill The stool and the bottom of the window will need to come into contact with each other when the window is closed and the window bottom must extend ½ or more past the new trim on each side of the window.