How to do modern interior window trim (extension jamb)?

Question

I have traditional interior window trim in my bedroom:

and want to replace them with extension jambs for a more modern look:

I’ve never done window trim and have never worked with drywall before but have seen a couple of great tutorials.

The reveal on my window measures 2”-2.5”. I’m pretty confident I can tear up the old trim, install corner beads if the drywall edges/corners are unfinished, lay down two coats of drywall compound (basically do a drywall return), and then cut-to-fit the extension jambs.

But I’m wondering how to get uniform spacing between the extension jambs and window frame.

Any additional tips? This project seems straight forward enough but I’d just like to cover my bases.

Answer 1

If the look you want is modern trimless, be careful on how you remove the jamb extensions. It looks like the window jamb may go over the wood jamb extensions.

You will not need to add drywall to the returns. Add plywood instead, this way you can add 3/4" 1/2" or 1/4" where needed and add shims if things are at an angle. Then add your corner bead to that, or even this...

Image courtesy Lowes

That way when the finished wood jamb is in place, the reveal, will be consistent all the way around and the dimension you wish to see.

When adding plywood or solid wood fillers you may need to keep it flush with the existing drywall to give either the corner bead or L bead some backing since it will be difficult to add a small sliver of drywall to the edge. It would be unnecessary to cut back the drywall, just to add more.

The L bead has a raised edge so the nail heads are below the raised edge so the nail heads do not get into the finish. This would all depend on what you have to work with. The standard corner bead may be the better choice.