If there is already a doorway between the house and the new addition you merely need to alter the frame to the size of your interior door, install an interior threshold and jamb, and hang the new door.
If you opted to move or enlarge the door, you will need to cut a new doorway or possibly even take out the entire common wall.
Whether you are using the same door, creating a new doorway, or removing the entire wall, strip exterior siding from house wall and re move insulation, wiring, or other obstructions.
When installing a new door, be sure of its exact size before framing rough opening. The rough opening is typically 2 inches wider than the door, to allow for two jambs, each ¾-inch thick, plus clearance. The height is typically 6 feet 10 inches above the subfloor to accommodate a 6-foot 8-inch door plus 2 inches for jamb, finish flooring, and clearances. Be sure to allow 1 additional inch for tile or for thick carpet.
Creating a New Doorway
If possible, the hinge side of the door should be located against an existing stud that's plumb. Otherwise, you must cut and toenail a new king stud, allowing 1½-inches inside for trimmer stud.
Cut and facenail trimmer stud in place (usually 82 inches long).
Mark location of opposite king stud on top and bottom plates by measuring from first trimmer stud a distance equal to rough opening plus 3¼-inches. Then install second king stud.
Cut 2 by 4 trimmer for second king stud. Its top should be level with top of first trimmer. Do not install yet.
Mark intermediate studs for cutting by marking each king stud where top of header will be and snapping a chalk line between the two marks. Then measure, cut, and install header. Snug it up against intermediate studs by setting one end on in stalled trimmer and forcing up other end with new trimmer.
Nail header and install cripple studs above both ends of it. Then toenail other cripple studs in place and remove the section of soleplate between trimmers.
Creating a Large Opening
Whether the beam for a large opening is installed when the walls are framed or after the shell is completed depends on the width of the opening and the structure of the house roof. If you are removing a bearing wall — one that supports the roof and /or any upstairs floors — get professional ad vice about shoring and removal techniques. If not, follow these steps.
Begin by erecting temporary shoring on the house side of wall to hold up ceiling joists that might be sup ported by wall. Support overhanging rafters on addition side similarly. Be sure temporary shoring has foundation support.
Mark dimensions of new rough opening on top plate and soleplate.
Remove studs. Cut and remove soleplate and top plate at marks. To prevent having to toenail rafters again, leave cap plate undisturbed unless it's necessary to remove it so bottom of beam will have sufficient headroom (minimum 80 inches).
Next, install studs or 4 by 4 post to support one end of beam. Cut similar support to size for other end, but don't install yet. Measure and cut care fully to allow for exact thickness of beam, excluding notches. It is also important to check under floor for support (minimum 4 by 4) directly beneath new posts all the way to foundation.
Notch ends of beam, if necessary, to clear top plates as it's snugged up against cap plate. (This step will not be necessary if there is room to conceal beam above new ceiling by resting it on top plates.)
With helpers, lift beam into place so one end rests on top of post you installed. Snug other end up by tap ping second post into position under it with sledgehammer.
The final step is to nail beam securely to any framing it supports. Use metal connectors to tie it to posts and top plates.