How to Cut Window Frame Molding

Window molding covers the space between the window casing (the edge of the wood that forms the immediate border around the window) and the surrounding wall. In addition to the aesthetic function of hiding that small space, it helps block the movement of air through the wall around the window. There are numerous ways to cut the trim around the window; using a four-corner miter is the simplest. Use pre-finished or pre-painted molding to save work later.

Things You'll Need

• Tape measure
• Pencil
• Flat trim molding
• Miter saw
• Hammer
• Finish nails
• Caulk

Instructions

1. Measure the width of the window opening at the top, from corner to corner, right at the edge of the casing.

2. Mark out the measurement with two marks on a piece of trim, with the measured distance between the two marks and at least a few inches of space outside of each of them. Put the marks along the bottom edge of the trim.

3. Set the trim facing up on a miter saw, with the marked bottom edge of it butted along the back rail of the saw. Slide the board so one of the marks is in front of the blade. Turn the blade to 45 degrees facing out, away from the middle of the board. Make the cut.

4. Position the second mark in front of the blade. Turn the blade so it's again pointing 45 degrees outward; this will be in the opposite direction from before. Make the cut.

5. Hold the cut molding up to the window, lining up the bottom edge of the trim with the top edge of the window casing. Set it so the angled cuts at each end of the board begin at the two corners and jut up and out from there. Hammer trim nails every 8 to 10 inches along the top and bottom edges of of the molding.

6. Repeat the whole process for each of the other three sides of the window. Nail the pieces up so that the angled cuts butt against one another to form the corners.

7. Caulk around the edges of the trim.

References

• Kelleher: Mitering Molding