What To Know About Interior Trim and Molding

Publish date: 2024-10-19

About 10 years ago, I remodeled a stair landing in a small Cape Cod-style home. It was a space between two upstairs bedrooms on either end of the home.

Though less than 100 square feet, it consisted of more than 80 pieces of trim and molding. There was beadboard (a type of paneling), baseboard, quarter-round, chair rail, rail cap, door casing and inset knee wall doors (small access doors). The job took several days, but the finished result was one of my favorite projects I’ve ever tackled.

For most homeowners, it’s not necessary to know all the nuanced intricacies of interior trim and molding. Here, I’ll list and explain what you need to know to make informed decisions about the trim and molding in your home.

What Is Interior Trim and Molding?

Interior trim and molding are the individual pieces of wood (or other material) that surround windows and doors, run along the floors and ceilings where they meet walls, and other areas throughout a structure.

While they might appear purely decorative, pieces of interior trim and molding actually serve important purposes. Trim and molding cover ragged, unfinished edges of drywall, fill gaps around door and window jambs, and generally dress up intersections of drywall, wood and other spaces that would be eyesores.

In some cases, moldings exist to protect the structure. The original purpose of paneling on the lower half of a wall was to protect brittle plaster from damage. For this same reason, many dining rooms and kitchens featured moldings that run horizontally around the room at the exact height a chair back would strike the wall, providing a protective buffer called chair rail.

Interior trim and molding is commonly made from pine, hardwoods such as oak, medium density fiberboard (MDF) and a hard plastic foam called PVC. MDF and PVC are the most affordable options. Pine is slightly more expensive but can be fashioned from several small lengths of wood spliced together. Hardwood is the most expensive option.

Interior Trim Right Below the Ceiling

In many homes, pieces of molding run along the wall where it meets the ceiling. It’s there to clean up the joint between the two planes. This trim is typically called crown molding, but there are three types:

Interior Trim Where the Wall Meets the Floor

You’ll commonly find trim where the wall meets the floor. It’s there to hide the gap between the bottom of the wall and the floor. Several types of interior trim serve this purpose:

Interior Trim Around Windows

Old Oak Flooring being Restoredwingedwolf/Getty Images

While it might not look like it, window trim actually includes several types of trim, each serving a purpose. These moldings work together to close the gap around the window, cleaning up the transition between the wall and the rough opening. These are the five moldings:

Interior Trim Around Doors

Interior doors generally come in assemblies that include the jamb, hinges and door. This assembly must be absolutely square for the door to operate correctly, but few rough openings are square.

The installer must use shims and a set of levels to install the door correctly, which leaves gaps around the jamb. Those gaps need to be covered, and that’s what interior door trim is for.

Other Interior Trim and Molding

Many other pieces of trim and molding can be installed in a home. While the list is long, the following are some of the most common ones:

Buying Interior Trim and Molding

Typically, interior trim and moldings are available in eight- to 12-foot lengths (aka sticks). The shorter lengths are more DIY-friendly because they fit in a smaller vehicle, but professionals generally prefer 12-foot lengths for convenience and less waste.

Pro tip: When calculating how much trim you need for a room, be sure to add at least 20 percent for mistakes and waste. So when ordering baseboard for a room that measures 10 feet by 10 feet (40 feet in total length around the room), it’s best to pick up an extra stick. The same applies to door and window casing, crown molding and other trim and molding pieces.

Note: You can also make simple trim in your workshop.

Installing Interior Trim and Molding

The carpenter uses a brad nail gun for the purpose of nailing the base molding trimphotovs/Getty Images

Beyond the sticks of trim or molding, be sure to have these things on hand before installation begins:

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