Unless your house is very old, you’ll have little problem finding a door to fit. The most common door height is 80 inches, although most are available 78 inches tall as well. Common interior door widths are 24, 28, 30, 32, and 36 inches. Height and width are often stated in feet and inches: 2-6 for 30 inches or 3-0 for 36 inches, for instance. Before you begin your DIY door installation, remove the old door and check that the doorway is square. If not, scribe and plane the door. If the doorway is well out of square, remove the casing, cut through the nails holding the jambs, and reattach the jambs so they are square. Now you’re ready to get started. We’ll show you how to install a door into your home’s existing opening. Editor’s Tip: If you have more than one or two doors to hang, consider investing in a hinge-mortising jig, which is a template for guiding a router to cut perfect mortises for hinges. Several models are available. The simplest (and least expensive) ones cut one mortise at a time, leaving the placement of the matching mortise up to you. More complex jigs come with multiple templates that will position matching mortises on the jamb and door edge. Most hinge-mortising jigs work with a router equipped with a template guide. The guide could be a roller bearing on the bit or a metal collar attached to the router’s base that surrounds the bit and runs along the mortise template. If the opening is finished only with drywall, you might be able to treat it as you would a rough opening and install a prehung door. If the rough opening was framed to a standard size and 1/2-inch drywall was used, check to see if the opening is square. If it is you can nail the door frame directly against the drywall opening. Otherwise, you’ll need to remove the corner bead and the drywall from the jamb and header faces to make room for shims. Check carefully for nails, then lay out the hinge mortises on the jamb. Rout close to the layout lines. Finish the mortises with a sharp chisel. Hold the door in the opening with shims and transfer the marks. After the door is hung and the lockset installed, rub a little lipstick on the bolt to mark the jamb for the strike plate. Using a spade bit, drill a 1-inch hole for the bolt; mortise the strike plate into the jamb with a chisel.
