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Introduction #
Casing one side of an 8'0" door is a staple task in finish carpentry, especially in new construction and remodels. This process involves installing trim around the door to cover the gap between the door frame and the wall, providing a polished look. A well-cased door enhances the aesthetic of any room and ensures a seamless transition between spaces. The single most important concept in this task is achieving tight, clean miters and ensuring that the casing is flush with the wall and jamb. This attention to detail is what separates professional results from amateur attempts. This guide covers an interior door; if you're casing an exterior door instead, see our exterior door casing guide for the extra weather-side details that come with it.
Before You Begin #
Before you case the door, confirm that the following prerequisites are complete.
Prerequisites #
- Drywall installation and finishing are complete.
- Flooring is installed, or allowances are made for its thickness.
- Door is hung and swings correctly.
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 gaps.
- Check for any separation between door casings and walls.
- Use a jamb extension if needed to case out a door properly.
If the opening you're casing has no door slab at all, our cased opening guide walks through that variation instead.
Tools #
- Miter Saw - for precise angle cuts on casing.
- Finish Nailer - for securing the casing to the wall and jamb.
- Level - to ensure the casing is plumb and aligned.
- Measuring Tape - for accurate measurements.
- Utility Knife - for trimming and scoring as needed.
Materials #
- Door Casing - typically MDF or prime pine for paint-grade applications.
- Finish Nails - 15-gauge, 2-1/2" for securing casing.
Installation Steps #
Step 1. Measure and Cut Casing #
Start by measuring the door opening and cutting the casing to length. Use a miter saw to cut 45-degree angles for the top corners.
- Measure the head casing first and cut to length.
- Cut side casings with mitered tops to match the head casing angles.
Step 2. Install Head Casing #
Position the head casing above the door, ensuring it is level and centered. Secure it with finish nails.
- Use a level to ensure the head casing is perfectly horizontal.
- Nail it into place with 2-1/2" finish nails, spacing nails every 16 inches.
Step 3. Attach Side Casings #
Align the side casings with the head casing miters and secure them to the wall and jamb.
- Check that the miters are tight and adjust as needed.
- Nail the casing to the jamb and wall, ensuring it is flush.
Step 4. Check and Adjust Alignment #
Ensure all casings are flush with the wall and jamb, adjusting as needed for a clean finish.
- Use a level to check for plumb and adjust if necessary.
- Ensure there are no gaps between the casing and the wall.
Pro Tips #
Pro Tip: "Some case miters look like shit, mostly basement and main floor" - Ensure your miters are tight and well-aligned to avoid unsightly gaps.
Pro Tip: "Cleaned up old casing to be reused" - Reusing old casing can save on materials and maintain consistency in appearance.
Common Mistakes #
- Mistake: Misaligned miters - This happens when cuts are not precise. Ensure your miter saw is properly calibrated.
- Mistake: Gaps between casing and wall - Often due to uneven walls or improper nailing. Check alignment and re-nail as needed.
QC / Punch Checklist #
- Verify all miters are tight and aligned.
- Ensure casing is flush with the wall and jamb.
