Interior Trim Work Basics

All the trim basics from start to finish, plus a clever way to get those miters tight

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We show you how to make crisp, sharp corners and tight joints when installing door trim, window trim and a three-piece baseboard. With a few basic carpentry tools and a little patience, you can trim out a room in a weekend. And with a little practice you can master the two key trim techniques, mitering and coping.

Tools Required

  • 4-in-1 screwdriver
  • Combination square
  • Coping saw
  • Drill bit set
  • Drill/driver - cordless
  • File
  • Glue
  • Hammer
  • Miter saw
  • Nail set
  • Putty knife

Materials Required

  • 3d finish nails
  • 4d finish nails
  • 6d finish nails
  • 8d finish nails
  • Wood putty
  • Wood trim

In this article, we’ll show you the basic steps for installing a wide trim around a door and window, complete with mitered corners. We’ll also show you how to put in a built-up baseboard made from a combination of three types of moldings.

You’ll need several key tools to do a first-class interior trim molding job. Use a power miter saw for clean angle cuts. A power miter saw vastly simplifies the job because it allows you to make incredibly accurate cuts in a matter of seconds. Even professionals admit they couldn’t do the same quality of work without one. If you don’t have a power miter saw, you can rent one. If you’re renting a miter saw, cut several scrap pieces to get the feel of the tool before cutting your trim.

You’ll also need a coping saw. This saw has a narrow blade and tiny teeth that allow you to cut tight curves; it’s available at any hardware store. And here’s a tip: Avoid that annoying trip to the hardware store in the middle of your project—pick up a couple of spare blades in case you break one.

The photo below illustrates the trim carpenter lingo we’ll use in this how-to article.

Photo tech art cutaway

Video: How to Trim a Door

Travis Larson, senior editor at The Family Handyman, will show you how to trim a door in about 10 minutes per side. The first time you do it, it will take longer but once you get the hang of it, you’ll be trimming out doors like a pro.

Project step-by-step (23)

Step 1

Get Set Up and Ready to Start

  • Clear the room you want to trim out.
  • Make your cuts in the middle of the floor.
  • Put a fan in the window if dust is a problem.

installing interior trim

Prefinishing Interior Trim Molding Saves a Ton of Time

Once you get your trim home, sand and stain or paint the trim before you install it. It’s a lot easier to finish trim before installation, working on sawhorses, than afterward, lying on the floor with sandpaper and a staining rag. Plus you can do a better job of sanding and finishing the pieces. After you’ve installed the pieces, be prepared to touch them up a bit. Do all the finish work in a well-ventilated area.

Step 2

Project 1: Interior Door Molding Case

Mark the Reveal

  • With a combination square, mark a reveal line 3/16 inch from the edge of the jamb.
    • Pro tip: Use a sharp pencil and position the marks in the corners and about every foot along the jamb edge.