How to Install Doorway Molding

Door casing, or trim, finishes the look of a newly installed door or can update the style of an older doorway. Casing conceals gaps between the door jamb and the rough opening.

Photo By: DK - Do It Yourself Home Improvement ©2009 Dorling Kindersley Limited

Photo By: DK - Do It Yourself Home Improvement ©2009 Dorling Kindersley Limited

Photo By: DK - Do It Yourself Home Improvement ©2009 Dorling Kindersley Limited

Photo By: DK - Do It Yourself Home Improvement ©2009 Dorling Kindersley Limited

Photo By: DK - Do It Yourself Home Improvement ©2009 Dorling Kindersley Limited

Photo By: DK - Do It Yourself Home Improvement ©2009 Dorling Kindersley Limited

Photo By: DK - Do It Yourself Home Improvement ©2009 Dorling Kindersley Limited

Photo By: DK - Do It Yourself Home Improvement ©2009 Dorling Kindersley Limited

Mark Inside of Door Frame

Mark 1/4 inch (6 mm) from the inside of the door frame. This will be your guideline for installing the trim.

Mark Trim

Place a piece of trim on each side of the side of the door, aligned with the 1/4 inch (6 mm) mark. Transfer the mark onto the trim.

Cut Each Piece

Cut each piece to length, mitering each end at 45 degrees.

Attach Side Casings

Nail each side casing in place, starting at the top.

Mark and Cut Top Piece

Mark and cut the top piece to length, mitering each end. The most important part of installing door casing is making sure that you cut the miters so that they fit together at the corners. Some DIYers choose to install the top piece first, making sure it is level and on the mark, before installing each side piece. With the top in place, you can use the top miters to mark the side pieces. If you need to make adjustments, use a sanding sponge to gently remove material and shape the miter.

Apply Wood Glue

Apply a line of wood glue to the end of each miter to help secure the pieces of trim to each other.

Attach Trim Pieces

Starting at the top, nail the sides in place, then fasten the top piece in position.

Finish

Fill the nail holes with spackle. Let dry and sand smooth.