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Casing Doors: Part 3

In Part 1 of this article, we reviewed the details of casing joinery and how to measure for new casing around a door frame. We also reviewed the necessary cut list, so that you can cut your casing right the first time. In Part 2, we moved on to the details of baseboard. Now, we’ll explore the best methods for installing casing, and the use of hand-driven nails—the preferred technique for working with soft wood.


Chapter 2: Part 3

A serial publication of excerpts from Trim Made Simple by Gary Katz

Training techniques for apprentice carpenters and serious DIYers


Installing Mitered Casing

New adhesives, fasteners, and clamps have changed the way carpenters install casing. I frequently pre-assemble large casings so that I can reinforce the miters and improve the joinery strength. But the old method of installing casing—starting with the head piece and then following up with the two legs, is still sometimes best, especially for smaller moldings. I’ll demonstrate both techniques here, so that you’ll be able to work with either type of molding. No matter which technique you use, always prepare the jamb first.

1. Mark reveals with a Trim Gauge. Before installing any casing, draw reveal lines on the jamb 1/4 in. back from the inside edge. A pair of scribes will do the job, but a marking gauge speeds up the task. The adjustable Trim Gauge can also be used for a variety of reveal or back-set layouts.

(Note: Click any image to enlarge)

2. Align the miters with the reveal marks. Tack the head casing to the jamb. If you’re using a nail gun, shoot one 23 ga. or 18 ga. brad near the center of the head casing.
3. Apply glue to the miters. Spread a thin layer of glue on both miters before assembling the casing.
4. Tack the leg casing to the jamb. Position the miter so the molding profiles align. Place the first nail about 4 in. below the miter. Drive a second nail about 8 in. below the first nail.
5. Spring Clamps are a must. A glue joint will not be strong unless it dries under pressure. Before driving more fasteners, install spring clamps on both miters. Adjust the clamps and the miters so that the profiles are aligned and flush.
6. Nail off the casing. Finish fastening the casing by driving brads or pin nails every 8 to 12 in. through the casing into the jamb. Fasten the casing to the wall every 12 to 14 in. To reach through the casing and the drywall, and penetrate the studs at least 3/4 in., use longer, 2 in. 15 ga. nails.

 . . .


Please don’t try anything you see in THISisCarpentry, or anywhere else for that matter, unless you’re completely certain that you can do it safely.

. . .

Hand-driven nails

If you’re installing molding on only one or two doors, don’t rush out and buy a nail gun. Driving nails by hand isn’t that difficult. To protect soft wood (and thumbs and fingers) from your hammer, use these techniques.

1. Prevent nails from splitting the casing. Nail gun fasteners have blunt tips, which prevent splitting even when nailing near the edge of casing. Hand-driven nails have sharp tips and will split casing if driven near the edge. Blunt the tips of hand-driven hails by tapping the tip with a hammer or by cutting the tip off with wire cutters.
2. Protect your fingers. Cut a narrow strip of cardboard. Poke your finish nail through the cardboard. While hammering, hold the cardboard and not the nail.
3. Plastic “Nail Grippers” are also available. They do an even better job of holding a nail firmly so it’s easier to position, start, and drive the nail. Plus, a Nail Gripper protects the casing from a missed hammer blow, or from driving the nail too far and striking the casing. ( $3.50)
4. For small pins and brads, use a Thumb Saver. ( $12.50/pair) This long-handled tool, with a strong magnet, secures any size nail and makes it easy to place hard-to-reach fasteners. It’s very handy for assembling picture frames, too.
5. Set all hand-driven nails. Drive each nail almost flush with the casing. Don’t hit the casing with a hammer. Instead, stop when each nail is 1/8 in. to 1/4 in. proud (above) the casing. Set each nail so the head is slightly beneath the surface of the casing. Use a nail set smaller than the size of the nail head.


Click the following link for the final part of “Casing Doors,” which will cover pre-assembly: casing and jigs!


14 Responses to “Casing Doors: Part 3”

  1. Sternberg

    I use cyanoacrylate glue on miter joints any more. I have found I can glue them together on the floor and carry them to be installed and they withstand some pretty rough handling.
    I can get a better installed joint that way.
    ‘I usually paint on a “size” coat on the end grain, and minute before final gluing and clamping on horses. They are ready to carry to install in about a minute.

  2. Sternberg

    This is the only picture I could find quickly of miters that I did that way, while it was in work.

  3. gary

    I usually rotate the nail so that the sharp edge cuts the wood fibers rather than rive them. Anyone can apply casing to a wall flush with the jambs. The challenge is to deal with glued drywall and out of plumb walls. I have used a simple wood block or combination square to mark reveals. No need for a plethora of special purposed tools.

  4. jim Caldwell

    Nice set of articles, I wanted to give you one more tip for the nailing/setting. I take a door shim and cut a 1/8″ notch about 1/2 way up the shim, or at about the 1/8″ or less thickness. I start my nail then slide the shim over the nail and hammer the nail flush with the shim.
    this leaves the nail 1/8 proud and prevents hammer lollies. I then set the nail in the normal fashion.

  5. Bill M

    I have a friend who has been doing work for me in preparation for selling my condo. He does some good work but I wondered if these two casing transitions could be done better. The picture here is of the casing for a bi-fold door that is too close to the front door. Is there a more creative and attractive way to transition this? The second is of scribe trim on my slider door and its transition to the casing around the door. Same questions: is there an alternative to what you see here? I appreciate the comments!

    • Gary Katz

      Yes, there is an alternative to what I see in your photos. But the alternative involves more than just the casing and baseboard. From what I can gather looking at the photo of your bifold door, you have bigger problems than just trim. But since your photos are both shot pretty close-up, I can’t tell just how involved those problems are. And I don’t want to see wider photos. Stuff like that upsets me–kind of like watching movies that have too much bloody violence. They keep me awake at night. :)
      Good luck!

  6. Bill

    Hi Gary,

    Ha! I gathered as much. The condo has some, shall we sy, “unique” features. Still, the condo is comfortable for folks who like condo living.

    So, could a more attractive solution be to bevel the edges on both pieces? Would it be practical to build out the jam on the left side in order to get a piece of casing? BTW, there are two other locations in the house where the carpenter had to rip the casing to make it fit. And the new tub I had put in 8 years ago? They had to cut a hole in my neighbors wall in order to hook up the plumbing, Or so they said.

    Thanks for you help.


    • Gary Katz

      I’m not sure if it would be practical to build out the jamb. Though that would be one fix. Raising the jamb would be another fix–so the casing would align at the head. But I don’t know if you have the room to do either. And frankly, I don’t want to know and neither do you. I suspect this is a rental? So just paint it and stop asking questions about it! :)

  7. Bill Milhoan

    Hi Gary,

    Thanks for your thoughts. I appreciate it.

    Nope. Not a rental…we are not permitted to rent out our units for the fear of what it could do to the property value. Another story…

    Take care,


  8. San Francisco Photographer - John

    Great post! I’ve always wondered about putty vs caulk. I fill nail holes with putty, and when I do have gaps between miters, I’ve been filling with putty. I seal the trim against the wall with caulk, but then I’ve seen a local GC team fill everything with caulk. And I’ve seen bad seems where the caulk seems to expand and bulge out over time. In other homes I’ve seen putty harden at joints and loosen up to eventually falling out. I know there is a max gap specified for most putties, but I never quite knew all the other true fine craftsmen approach to this sort of thing.

  9. Dave Joson

    What style of door molding did you install in your demo? I have been looking for that molding style everywhere without luck!
    Thanks, Dave

    • Gary Katz

      That’s a very common profile, call “Three Step”, at least that’s what we call it on the west coast. WindsorONE makes that pattern with a square edge, as part of their Colonial Revival collection–

  10. Michael B. Hess

    “Tack the leg casing to the jamb…Place the first nail about 4 in. below the miter. Drive a second nail about 8 in. below the first nail.”

    I’m using old-fashioned hammer and nails. What size nail do I use to attach the side casing to the jamb? I’m thinking 4D, but I’m wondering if that’s the correct size. Thanks in advance.


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