how to put trim on a doorway

How to Install Door Trim: A Step-by-Step Guide

By William ClarkMarch 2, 2026

Transforming the appearance of your home often starts with the smallest details, and one such detail is the trim around your doorways. Installing trim not only enhances the aesthetic appeal but also adds a professional touch to your space. So, let's dive into a step-by-step guide on how to put trim on a doorway, ensuring your home looks its best.

Before you start, gather your materials: baseboard trim, miter saw, nail gun, finish nails, wood glue, sandpaper, and paint or stain. Safety first, so ensure you're wearing appropriate gear, including safety glasses and gloves.

Preparation and Measurement

Accurate measurement is key to a perfect fit. Start by measuring the width and height of your doorway. These will be the lengths of your baseboard trim.

Door Trim Makeover — Before & After DIY Transformation

Next, measure the diagonal of the doorway. This measurement will help you create a perfect 45-degree miter cut for the corners.

Cutting the Trim

Using a miter saw, cut the baseboard trim at a 45-degree angle. The long point of the miter should be on the outside edge of the trim for the top piece. For the bottom piece, the long point should be on the inside edge.

the measurements for wood framing are shown in this photo

an open door with the words diy door casings the easy way

Ensure the miter saw's fence is set to the correct depth to avoid cutting through the entire width of the trim. Make your cuts one at a time, checking the fit as you go.

Dry Fitting

Before applying any glue or nails, do a dry run of your cuts. Place the trim pieces in the doorway, ensuring the miters fit snugly at the corners.

If the fit is not perfect, adjust your cuts as needed. Once you're satisfied with the fit, remove the trim pieces and set them aside.

Interior Door Trim Ideas: Simple DIY Upgrade with Big Impact

an entry way leading to a kitchen and living room with white walls, wood flooring and stairs

Enhance Your Doorways: DIY Decorative Molding Installation

Installing the Trim

Now that your trim pieces are cut and fit perfectly, it's time to install them.

Start by applying a bead of wood glue along the back edge of the top trim piece. This will help secure the trim and fill any small gaps.

Attaching the Top Piece

Using a nail gun and finish nails, attach the top piece of trim to the doorway. Nail at an angle, driving the nail through the trim and into the door frame. Space your nails about 6-8 inches apart.

the words door trim and casing are overlaid with images of different types of doors

the interior door trim is being installed in an empty room with wood floors and white walls

an open door with the words dress up your doorways add casing and corbls

the corner of a room with a stained glass window and white trim on the wall

Simple Door Trim = Instant Modern Upgrade!

DIY Doorway Trim - A Transformative Project For Christmas

an easy budget update sign hanging on the wall in front of a mirror that says easy budget update

Finish Carpentry Trim: 14 Easy DIY Projects | ThePlywood.com

Easy DIY Door Trim To Add Old House Character - An Oregon Cottage

After nailing, use a small piece of sandpaper to lightly sand any raised grain or glue residue.

Attaching the Bottom Piece

Apply wood glue to the back edge of the bottom trim piece and attach it to the doorway, just like the top piece.

Once both pieces are attached, use a small paintbrush to apply paint or stain to the miter joints. This will help hide any nail holes and give your trim a finished look.

Finishing Touches

After the paint or stain has dried, lightly sand any raised grain with fine-grit sandpaper. Wipe away any dust with a damp cloth.

Finally, apply a topcoat of paint or polyurethane to protect your trim and give it a beautiful, finished appearance.

Stepping back, you'll appreciate the transformation a simple trim installation can bring to your doorway. It's a small detail that makes a big impact. Happy DIYing!