A door jamb is also known as a door frame and is a simple and basic home construction job that requires a few standard tools and a bit of home carpentry skill. This is a home improvement project that can be completed in an afternoon.
Step 1 – Measure Opening
Measure the opening you intend for the door. Standard door widths are 24, 30 and 36 inches wide. Standard interior door height is 80 inches. You will need to construct your opening to accommodate the size door you intend to install. Also, when measuring for the door opening, add 6 inches to the width to accommodate the door framing, and 1 inch to the door height also to accommodate framing. Mark cutting lines.
Step 2 – Saw Opening
Using a reciprocating saw or circular saw, cut the opening for the new door. Carefully insert the blade at the beginning of your door opening. Cut both sides and then the top until you have the entire door opening cut. Push through and remove the wall board.
WARNING: Before cutting, take time to ensure that you will not be cutting into a wall area that contains plumbing or electrical wiring or other detrimental structures that would prevent placing a door in that location.
Step 3 – Install Framing Boards
Measure and cut 2 x 4-inch boards. These will be used as door studs along the side of the door opening. Insert the studs into the door opening. Double the boards on each side of the door opening.
Step 4 – Install Header
Cut two 2 x 4-inch boards to length to form the header of the door. Use nails or screws to attach these two boards together. Measure from the ceiling to the top of the header. Cut three studs to this length. These will be your cripple studs. Nail one stud on each side of the door opening between the header and the ceiling and the third cripple stud in the center of the header, placed from the header to the ceiling. Nail the studs with the nails at an angle for extra strength and to attach them to the ceiling.
Step 5 – Cut Door Frame
Using ¾-inch lumber, construct a frame for the opening. The width of the boards should include the actual frame, plus the thickness of wall covering materials (wall board, paneling or other materials). You will need to cut a total of 4 framing supports, 2 for the sides and 1 for the top and 1 for the bottom of the door frame.
Step 6 – Install Frame
Nail the framing piece that goes along the header first. Next, temporarily nail one side framing piece in place and then the other. Use the carpenter square and level to make sure that the framing is square and plumb before firmly nailing the framing permanently into place. If needed, add shims to bring the pieces into square and plumb before nailing with finish nails. Once you have the top and sides in place, then attach the bottom framing piece into place.
Step 7 – Finish Door Jamb
With the frame complete, then you can install any desired molding to complete and finish the entire door jamb. Nail the molding with countersunk finish nails.