Introduction #
Casing one side of a 6'8" door is a fundamental task in finish carpentry, often required in new construction and remodel projects. This task is typically performed after the door has been hung, and it involves installing trim to cover the gap between the door jamb (the frame the door hangs in) and the wall. The casing not only enhances the aesthetic appeal of the door but also provides a finished look that complements the rest of the interior trim work. This guide covers an interior door; if you're working on an exterior door instead, see our guide on installing exterior door casing, since the materials and clearances are different.
In a production environment, speed and consistency are key. The single most important concept to master when casing a door is achieving tight, clean miters (the 45-degree corner joints where two casing pieces meet) at the corners. This is what separates a professional finish from an amateur one. Proper alignment and a snug fit prevent gaps that can lead to callbacks and ensure a seamless transition between the door and the wall.
Before You Begin #
Before you case the door, confirm that the following prerequisites are complete. If you're trimming a doorway with no door at all, use our cased opening guide instead, since the layout works a little differently without a jamb to reference.
Prerequisites #
- Door is properly hung and swings correctly
- Drywall is finished and painted
- Flooring is installed
What You Need To Know #
When you case the door, understanding these core techniques will save you time and prevent callbacks.
- Ensure case miters are properly aligned to avoid unsightly gaps
- Check for gaps between door casings and walls, and address them for a clean finish
- Use a jamb extension if necessary to ensure the casing fits properly
Tools #
- Miter Saw - for precise cuts on casing
- Finish Nailer - for securing the casing to the jamb and wall
- Measuring Tape - to ensure accurate cuts
- Level - to check for plumb and level installation
Materials #
- Casing - typically MDF or Prime Pine, depending on the project specifications
- Finish Nails - 18-gauge, 2-inch nails are standard
Installation Steps #
Step 1. Measure and Cut the Casing #
Start by measuring the height and width of the door jamb. Cut the casing to size using a miter saw, ensuring a 45-degree angle for the top corners.
- Measure twice to ensure accuracy
- Cut the top piece first, then the sides
Step 2. Install the Top Casing #
Position the top casing piece on the jamb, ensuring it is centered and level. Secure it with finish nails, spacing them approximately every 12 inches.
- Use a level to ensure the casing is straight
- Check the alignment with the side jambs
Step 3. Install the Side Casings #
Align the side casing pieces with the top piece, ensuring tight miters. Secure them with finish nails, starting from the top and working your way down.
- Ensure the miters are tight and flush
- Check for plumb with a level
Pro Tips #
Pro Tip: "Case it the way you normally would, it's just really skinny." - When working with smaller trim, maintain your standard casing techniques for consistent results.
Pro Tip: "Some case miters look like shit, mostly basement and main floor" - Focus on perfecting your miter cuts to avoid unsightly gaps.
Common Mistakes #
- Mistake: Misaligned miters - Ensure cuts are precise and use a miter saw for accuracy.
- Mistake: Gaps between casing and wall - Fit the casing tight to the wall before nailing it off, so there's no gap left behind.
QC / Punch Checklist #
- Check that all miters are tight and aligned
- Ensure there are no visible gaps between the casing and wall
