Whether purchasing an interior or exterior door, most are marketed as “pre-hung;” a single unit complete with frame. Hinges are usually already installed on the door; the door already attached to a frame.

Pre-hung interior doors usually arrive from the factory with double-headed nails driven through the frame and slightly into the edge of the door. This is to hold everything in place during shipping. The nails should be removed before installing the door.

Exterior doors, on the other hand, come with a retaining bracket. This should be left in place until installation is nearly complete.

While height is fairly standard, doors do come in a variety of widths. The opening should be prepared and framed in such a manner that whatever width door you have chosen will fit into the opening with minimal shim requirement.

Standard pre-hung doors have 4½ -inch jambs for use with 2x4 framing and ½-inch wallboard. If your walls are thicker, you will need to special order doors to fit. Or else fur the door jamb out flush with the wallboard using jamb extensions, or furring strips.

Whether installing a door in a partition wall (non-load bearing) or in an exterior (load bearing) wall, the principle is the same. The rough opening is framed using a king and jack stud on each side, with a header and cripple studs above. Working out from the door, the door jamb will be shimmed and nailed to the jack studs on either side. The jack studs will hold up the header. The king studs run along side the jack studs, from bottom plate to top plate.

The header bears all of the weight of the structure that is directly over the door. The load is transferred to the header by short cripple studs between the header and the top plate; jack studs transfer the weight down to the bottom plate.

Measure Accurately

The rough opening after framing needs to be the width of the door and frame (the frame is also referred to as the door jamb), allowing an extra ½-inch on each side and above the door. Also keep in mind that 2x4 studs are not 2x4-inches in measurement. They are actually closer to 3 ½-inches by 1 ¾-inches; this can vary slightly due to shrinkage.

For accuracy, mark the width of the door at the desired position on the sill plate, plus the additional ½-inch on each side. Mark the width of your jack studs (measure the actual studs you plan to use), and then do the same for the king studs.

For example: for a 4-foot pre-hung door (measured from the outside jamb on one side to outside of the jamb on the other side) you will add 1-inch (1/2-inch for each side), plus 3 ½-inches for the thickness of the two jack studs (1 ¾-inches each; but be sure and use the actual measurement for the studs you will be using), plus 3 ½-inches for the thickness of the two king studs; 1¾-inches per side. But again, use actual measurements.

The first set of marks should be 4-feet apart, the next set should be 4-feet, 1-inch apart; the next set should be 4-feet, 4 ½-inches apart. The final marks should be 4-feet, 8-inches apart.

Any framing studs located in the area included in the rough opening will need to be cut, and the bottom portion removed. You will need to allow for the height of the door plus ½-inch, plus the size of the header. For example, if you are using 2x6s for a header, you would need to include the 6-inch measurement (door height, plus ½-inch, plus 6-inches).

Since you will be removing the bottom plate and the door threshold will be sitting on the floor, you must measure from the floor to the cutting mark on the framing studs. Make sure that your line is plumb and square across the studs you will be cutting. What remains will become cripple studs between the header and top plate.

Beginning with the widest measurements, nail the king studs into place; running from bottom plate to top plate, flush with the out side marks. Make sure each is plumb before nailing. The jack studs must be cut to the proper length. Since they will sit on the bottom plate, you will need to allow for the thickness of the plate, as well.

The length of the jack studs will be the height of the pre-hung door set; to the top of the jamb, plus ½-inch, minus the thickness of the bottom plate. Nail the jack studs to the inside of the king studs.

Special Considerations - Balloon Framing

Different techniques are used for exterior home door installation, depending upon house structure type. Take a balloon frame house, for instance. Rough opening and how to install a door differs from a more modern house design. Follow the directions in this section for older home door installation success.

Almost all modern construction utilizes platform framing. However, older structures may have been constructed with balloon style framing, commonly used during the 1930s and 1940s.

When adding exterior door framing for a rough opening in balloon framing, follow this procedure:

• Remove interior walls to expose framing. Select two studs to use as king studs. The distance between the selected king studs must be at least 3-inches wider than the required rough opening. Measure from the floor; mark the rough opening height on the selected king studs.
• Determine the size header required. Using the marks on the king studs, measure up; mark the top of the header on the king studs, and on any studs in between.
• Cut open the subfloor and remove fire blocking with a reciprocating saw to gain access to the sill plate for installing jack studs. If more than one wall stud is removed, you will need to make temporary supports (see “Making Temporary Supports” for balloon framing).
• Cut the intermediate studs on the top header markings using a circular saw, but leave the king studs intact. Make additional cuts approximately 3-inches below the first cut, and 6-inches above the floor. Finish the cuts using a handsaw. Knock out the 3-inch sections with a hammer; remove studs with a pry bar.
• Cut jack studs to fit from the sill plate to the rough opening marks on the king studs, and then nail them in place to the king studs. Use10d nails spaced every 12 inches.
• Install the header on top of the jack studs. Nail it to jack studs, king studs, and cripples using 10d nails.
• Mark the rough opening width measurement on the header; use a plumb bob to mark the opening width on the sill.
• Install additional jack studs if necessary in order to frame the proper rough opening size. Toenail the jack studs to the header and sill plate.
• Install blocking between the primary jack studs and additional jack studs on each side of the opening using 10d nails. Make sure to install blocking at the location points of hinges and locksets.
• When you are ready to install the door, remove exterior wall surfaces. Cut the remaining ends of intermediate studs flush with the tops of the floor joists using a handsaw or reciprocating saw.
• Install 2X4 nailing blocks next to the jack studs and joists, flush with the tops of the floor joists. Replace fire blocking.
• Install plywood over the joists and blocks to make a level surface for the door threshold.

Adding the Header

Quick and to the point, this section on door header framing – for both a load bearing wall and non load bearing wall – tells how to gauge accurate door header sizing. It also includes information on door header construction; whether commercially manufactured or self-made.

When it comes to door framing for a non-load-bearing wall, standard 2x4 framing studs are adequate as a header. When framing in a load-bearing wall, however, special consideration must be given to proper header size. The width of the rough opening will determine the minimum header size for that width.

Headers can be obtained in the various sizes made from engineered beams, (constructed by laminating layers of wood together into a beam). Or they can be made by gluing and screwing framing lumber together with ½ inch plywood set between, using two 2x4s, 2x6s, etc. The piece of plywood is cut to the same size as the lumber. Width requirements are:

• Up to 3 feet – 2x4
• 3 to 4 feet – 2x6
• 4 to 6 feet – 2x8
• 6 to 7 feet – 2x10
• 7 to 8 feet – 2x12
• 8 to 12 feet will require special engineered wood header beams

The header should be cut to fit between the king-studs, resting on top of the jack studs. Nail through the outside of the king studs into the ends of the header using 10d nails. And then nail the jack studs and cripple studs to the header.

Using a reciprocating saw, cut the bottom plate flush with the inside edge of the jack studs, and remove it. The rough opening is now ready to receive the door.

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