Installing Interior Door Molding

Interior door molding hides ugly gaps between a door's jamb and the door frame's rough-in opening. During the rough-in phase of a building's construction, carpenters frame out openings in the walls for doors and windows. To ensure the door and windows fit in the rough-in openings, carpenters give approximately 1 inch of extra space to the height and width measurements. Door moldings have many looks and shapes, ranging from plain smooth cuts to molding with deep intricate carvings.

Things You'll Need

• Tape measure
• Pencil
• Miter saw
• Platform
• Razor knife
• Hammer
• 4d finishing nails
• Nail set
• Caulk

Instructions

1. Measure 3/16-inch from the finished edge of the door jamb toward the drywall, using a tape measure. Use a pencil to make check marks this distance from the edge of the jamb at the two corners above the door, and on the sides make them at the top corners, the midpoints and the bottom ends.

2. Measure the exact width of a piece of door molding.

3. Measure from the floor to the check mark above the door on the right side of the top piece. Add the molding width. Draw a pencil line on the outside edge of a piece of molding at the total length. Label this molding "right side."

4. Measure from the floor to the check mark above the door on the left side. Add the molding width. Draw a pencil line on the outside edge of a piece of molding at the total length. On the back side of the molding label "left side."

5. Measure between the two top check marks on the jamb's sides. Add twice the width of the molding. Draw a pencil line on the outside edge of the molding at the total length measurement. Label "top" on the back side.

6. Set up a miter saw. A miter saw needs electricity, a firm flat surface to rest on and a platform for the material on both sides of the blade. Plug the miter saw into an electrical outlet. Build the platform the same height as the saw's cutting platform.

7. Turn the cutting platform to the right 45-degree mark. An arrow will point to a series of numbers representing cut angles. Once the arrow reaches 45 degrees, lock the platform into place, often using with a wing nut or clamp to hold it in place.

8. Turn the power to the miter saw on and allow the blade to reach its cutting speed; this may take a few seconds.

9. Place the "right side" door molding on the saw and material platforms. Line up the mark on the back of the molding with the "cut here" mark on the platform near the blade. Push down on the saw's handle until the blade has completely cut through. Cut the right side of "top," using this saw angle.

10. Turn the saw to the left 45-degree mark and lock it into place.

11. Cut the "left side" and the left side of "top" with the miter saw at the pencil marks on the back of the molding. Turn the saw off.

12. Cut away any drywall that extends past the width of the door jamb with a razor knife. Visually inspecting the drywall fit with the cut door trim will help find hidden high spots that will show up in the finished product.

13. Tack the "top" piece into the jamb above the door. Use a hammer to nail 4d finishing nails 1 inch from each cut end. The bottom of the molding should just cover the top pencil lines and the bottom corners should line up with the top check marks for both sides.

14. Hold the "left side" piece against the left side of the door jamb. Line up the "top" and "left side" corners. Drive a nail through the molding and into the casing at the top corner. Adjust the middle of the molding until its edge covers the pencil line and tack the molding into place near the mark. Adjust the bottom of the molding to cover the pencil mark and tack it into place.

15. Tack the "right side" into place, using the other side as a guide.

16. Drive a finishing nail between each tack nail, for a total of five on each board.

17. Countersink each nail, using a nail set. Place a nail on the driven nail's head. Lightly tap the loose nail until the driven nail's head has penetrated the molding's surface. Do this for every nail.

18. Caulk the space between the molding and the jamb, in the miter cuts and between the drywall and the molding. Apply a bead to one seam at a time. Before moving to the next seam, run a finger across the bead, removing the excess caulk and smoothing the bead.

Tips & Warnings

• Wear safety goggles when using a miter saw.

References

• HammerZone.com: Installing Hardwood Interior Door Casing
• Home Addition Plus: Installing Interior Door Trim
• The Home Improvement Web: Install Mitered Door Casing
• Install Molding: Using a Miter Saw

Resources

• Bob Vila: Cutting and Installing Door Trim