How to Install Door Casing Molding

Installing the door casing molding, also known simply as door casing or casement trim, is a simple operation for any DIY enthusiast. Although this is relatively easy, you should be prepared by having the right tools and materials. You also need to know a few things before starting your project. Follow these easy steps to make your installation a breeze.

Tools and Materials

  • A measurement device (tape ruler)
  • Primed wood trim (other options include vinyl or composite)
  • Miter saw
  • Nail set
  • Hammer
  • Painter’s caulk
  • Finishing nails

Step 1: Pre-paint the Trim (optional)

Skip this step if you are installing the door casing while painting walls or building a new house. Pre-painting will make it easier, because you will only need to touch up the paint after you are done.

Step 2: Taking Measurements

Decide how much of the doorjamb you want to leave revealed, this is important because it will tell you how long each piece of the door casing will need to be. Take measurements of the top part or the door, stopping at the distance you decided to leave for the doorjamb. Now take measurements of each side of the door from the bottom up and add about a quarter of an inch. This will help if your measurements aren’t exact. Ending up with a longer piece is easy to fix by additionally cutting it, having a piece too short means you will throw it away.

Step 3: Cut and Fit the Top Trim First

You will start by cutting the top part of the door casing first. Many people start with the sides and then struggle to fit the top. Starting with the top will make it easier for you to add the sides. Using the miter saw, cut 45-degree angles in your top trim. This means the top thicker side will be longer. Now set it in place and nail it down using your hammer and finishing nails.

Step 4: Cut and Fit the Side Trim

After setting the top trim, measure the sides from the top trim down and check with your previous measurements. Cut the side trims at a 45-degree angle using the miter saw, making sure you have the correct angles to fit the top trim. The door casing will have the angle pointing in the other direction of the door it is set. So the right trim will have the longest part on the right and the angle pointing to the left. In order to reduce the chance of a mistake, cut the trims just a bit longer first. Then just keep cutting more until they fit perfectly. Nail them down using the hammer and finishing nails.

Step 5: Finishing Touches

Take your nail set and hammer and gently tap each of the nails you have previously used to set the trim in place. This will make the nails go inside the trim where they can be easily masked and covered. Use the painter’s caulk on all the nail holes and to fill the gaps between the trim pieces. Now either paint or apply finishing touches to the trim based on whether you decided to pre-paint your door casing or not.