No weird angles or expensive rosettes to buy here. Just cut the two vertical side pieces of casing so that they reach (but do not extend beyond) the top of the door opening.

Then cut a header piece (the horizontal top piece) so that it equals the horizontal door opening + the twice the width of a side casing + plus some whatever extra amount that tickles your fancy.

Butted door casings have a utilitarian look that can look cheap.  So, use real moldings, not dimensional lumber (i.e., 1×4s).

By that last time, I’m talking about the extra amount that extends beyond the side casings. It can be anything you want, but you’ll probably not want to go crazy here. This is all for show, and gives your butted door casing a little fancy finish: a quarter-inch on each side is enough.

Admittedly, mitered casings are not too hard. For goodness sake, it’s just a 45 degree angle cut.

But for some reason, those mitered casings sometime go wrong. Something is out of square—the door framing, your brain, or something—and those two angles just don’t come together.

Butted door casings save you from all that. The horizontal and the vertical door casings meet at a 90 degree angle. Except, of course, there is a blank space where they are supposed to meet. Hard to describe, so look at the image above. So in that blank space you drop a corner block, or rosette. Rarely do you have any gaps with this butted door casings plus rosette design. Terminology: this isn’t really a true butted door casing—that’s another thing we cover—but it’s just what I call it.

But, yes, like anything, there are some drawbacks with the butted door casings plus rosette design:

• Those rosettes can be expensive.
• This style tends to be more classic and traditional. If you have a contemporary style house, this may not work.