Measure and cut the casing
Often referred to as door and window trim, casing hides the joint between the drywall and the door or window jamb. Spend some time at your local lumberyard and you’ll see all the styles and grades of casing, including the type that’s installed at the factory on many prehung doors. Solid wood casing can be used if you want to leave the wood natural. Paint-grade trim— made from MDF or from shorter pieces of wood that have been finger-jointed together—is also available and costs less. Some people prefer a plain, narrow, simple style, whereas others prefer wider, more complex profiles. Purchase 14-ft. lengths to minimize waste. Another option is to buy 7-ft.-long pieces that have a 45-degree miter precut on one end. These pieces are used to trim around doors.
PLAN FOR A REVEAL. When running casing, carpenters commonly leave what’s called a reveal, which simply means that one piece of wood is held back a bit so you can see the edge of the piece beneath it. The idea is to create a shadow line, which produces a sense of depth and adds visual interest. This is done even on simple trim in an affordable house. To mark the setback for the casing on the jamb, use an adjustable combination square. Set it at about 3/i6 in. to /4 in. in from the inside edge of the jamb—whether it is on a door, a window, or an attic access—and mark a pencil line in several places (see the illustration at right). With a little experience, you’ll be able to mark a setback by eye, without a square. The casing is cut and nailed to that line.
MARK AND CUT THE CASING. Now it’s time to cut the side and head casings to length. Cut and nail the casing with its thinner edge facing in, toward the door opening. The baseboard trim butts into the wide edge of the casing at the floor line. To find the length of a piece of side-jamb casing, measure from the floor to the horizontal reveal line at the top of the door or window. That measurement is the distance to the short point of the miter cut.
Another way to obtain this measurement is to hold a piece of casing alongside the door or
across the head jamb and mark the short end of the miter cut at the /4-in. reveal line (see the bottom left photo on p. 252). Make a diagonal mark on the casing to show which way to make the cut. Just make sure the mark will be cut off, so it won’t be visible once the casing is installed. Take the casing stock to the chopsaw and make the cut. Side casings are cut in pairs, one for the jamb on the right and one for the jamb on the left. Take your time. Work slowly. Make sure you are cutting in pairs.
The same technique can be used for windows with sills and jambs. Measure from the sill to the horizontal reveal on the head jamb (for side casings) and from one vertical reveal line to the other on the side jambs (for head casings). All these marks are made from heel to heel, or short point to short point, of the miter cut.
In theory, once you know the length of one piece of casing, you should be able to set up
Hand-nail trim with care. When using a hammer to attach trim to the wall, leave the finish nail about /8 in. proud of (higher than) the surface of the wood, then use a nail set to drive it about Уг in. below the surface. The hole will be filled with putty and sanded prior to painting. Take care not to miss the nail and leave a hammer track in the wood surface.
at the saw and cut every piece for doors and windows of the same size. This can eliminate repetitive measuring and lots of time spent walking back and forth to your saw. In practice, side casings may vary slightly in length. But small gaps at the floor line will be hidden by carpeting or cut to uniform distance to accommodate wood or other finish flooring. Find out what carpenters are doing in your area.