 Opening up a wall to create a new doorway can put a whole new spin on the way traffic moves through your home, sometimes making rooms more accessible and therefore usable. But before you cut a hole in a wall to add a doorway, be clear about what you might encounter.
Walls conceal a host of surprises, including wiring, pipes, and ducts that almost inevitably end up being just where you want the door to be. Investigate where these or similar obstructions are located before determining where your new opening should go. See more about Locating Pipes & Obstructions in a Wall. If you find pipes, ducts, or extensive wiring in the way, the easiest and least expensive option may be to modify your plan for the door's location.
Rerouting utilities can be quite involved and is often a job for a contractor, unless you are comfortable with a variety of do-it-yourself tasks. This type of construction usually requires a permit and is regulated by local building codes.
It is relatively easy to replace a window with a door. For instance, if your breakfast room has a 6-foot-wide sliding window that overlooks the backyard, you could replace it with a 6-foot sliding door. The framing, hidden behind the drywall, is already nearly complete. To prepare the area, you would just remove the window, the wall's surface material, and the studs below the window.
It is also fairly simple to install an interior door if the wall is not a bearing wall. Most interior walls, called partition walls, do not carry the weight of the roof framing, though a major central wall, such as that along a hallway, is likely to be bearing. The project shown here depicts the installation of a door in a non-load-bearing partition wall.
Doors are sold individually or as pre-hung systems, which come already hinged in a jamb and frame. The latter one is the easiest type to install. When you buy a pre-hung door, the manufacturer can provide you with the rough opening dimensions necessary for the structural framing. Normally, you will need to remove the wall covering for at least the rough opening plus 3 inches on each side and across the top for framing. If the door is going into a bearing wall, the rough opening may need to be even taller to allow for a header.
Often it is best to remove the wall covering from floor to ceiling between two bordering studs that will remain in place. Add 6 inches to the rough opening width, center this dimension on the wall where you want the door, and mark both sides. From those marks, tap a nail through the wall covering, working away from the center, to find the nearest studs (the new king studs). Lay out vertical cuts centered on these studs.
To remove drywall, just cut along your outline with a utility knife and pry the cut panels off the studs. To remove plaster and lath, cut through the lath with a saber saw or reciprocating saw equipped with a blade made for the job be sure to wear safety glasses, a dust mask, and gloves. To prevent unnecessary vibration, hold the saw's foot plate firmly against the plaster. Then use a prybar to pull down chunks of the plaster and remove the lath from the studs.
Finally, be aware that when you remove a section of wall to install a new doorway, the floor must be finished where the wall once stood.
| 1. After covering the floor with a drop cloth, use a sharp utility knife to score deeply into the drywall along your vertical layout lines. Make several passes if necessary to cut all the way through the material. Remove the drywall. | 
| | 2. Use a reciprocating saw to cut off the studs that are located within the new opening. (Note: If the wall is a bearing wall, the ceiling must be supported first.) Twist the stud pieces, and pry them away from the plates. |  | | 3. Mark the placement of new studs on the plates, using a pencil and a square. Where the doorway will go, cut away the plate using a reciprocating saw. Be sure the remaining parts of the plate are fastened firmly to the floor. |  | | 4. Toenail the new king studs to the plate (cut them for a tight fit). It's easiest to pin the stud in place with 8d nails at the front and back edges before toenailing each side with two 10d nails. Make sure the studs are plumb before nailing them at the top. |  | | 5. Nail the trimmer studs to the king studs, and then nail a flat 2-by-4 header across the top, driving two 16d nails down through each end and into the tops of the trimmers. | 
| | 6. Measure for short cripple studs between the header and the top plate. They should be positioned to maintain the typical stud spacing of 16 inches from center to center. |  |
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