Do I need to remove drywall before casing an opening?

Question

The entry/opening to my dining room is currently finished with drywall. I am looking to add casing to up the esthetic. I am wondering if I can nail the jambs over the drywall or if I have to remove the drywall and nail directly to the header and wall studs. Thanks in advance for the advice.

Answer 1

No, removing the drywall isn't required.

It will narrow the opening slightly but you should have no issues nailing it over the drywall. Think about how standard doors are trimmed out, over the drywall.

You might want to run some 2" nails through the jamb (depending on your material thickness) though so you have good penetration and your trim doesn't come loose.

Answer 2

You don't need to remove the drywall, but I strongly encourage you to remove the corner bead. It adds substantial thickness to the opening and taper to the wall. Run a long straightedge across the wall and the opening to see what I mean. There will be ski jumps at each side of the opening which make it difficult to achieve a reasonably square jamb/casing/wall interface.

So...

1. Lay your casing against the wall in its final resting place and put some masking tape markers at the outer edge.
2. Cut through the drywall mud about 1/2" inside that tape line on all faces of the drywall to a depth of about 1/8". This will prevent excessive damage and create a clean line on which your casing will rest.
3. Using a hammer and a flatbar or other prying tool, dismount the corner beads. If they're screwed on, pull the screws first. Nails can usually come off with the bead strip.
4. Scrape away any remaining loose material and vacuum up the mess.

Now you can case the opening without goofy angles, and your jambs will be the appropriate depth. Also, you might decide that removing the jamb-side drywall is easy enough at this point that you'd rather regain the inch of opening width. A few nails or screws and it's out, though you'll probably have to trim back the wall-side drywall too.

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Trim Tips

• Don't use a lot of nails through the jamb. They really show due to the way light travels between rooms. Six is plenty, and 18 gauge is best in a 2" length. The casing provides much of the mounting stability.
• Shim for plumb. Use a long level to assess the rough framing and add shims to deal with lean and twist as needed. You want the jamb plumb and square with the wall (disregarding any remaining ski jump).
• Skip nails altogether in the head jamb unless it's over 36" wide. Set the side jambs, then shim the head jamb down tight on it. The casing does the rest.
• Use 1¼" or 1½" nails through the casing into the jamb, and 2" or longer through the casing into the framing.