How Door Frames Are Built

Choosing quality lumber is the basis of a good door frame.

Door frames are essential to the security of any home. Construction of the door frame begins in the wall framing process. Making sure that all framing members are square, plumb and level. Accuracy in the width of the opening is key to proper installation of the door jamb, sill and threshold.

Wall Framing Studs

Door frame construction begins with two pairs of studs. They are cut to length to inch fit between the top and bottom plates of the wall, typically 93 inches. The two outside studs are called king studs, and they are spaced 3-½ inches wider than the outside of the door jamb. The inside pair of studs are known as the jack studs, and they are spaced ½ inch wider than the outside of the door jamb.

Door Frame Headers

Door frame headers are built in two ways. Simple passage door headers are double 2-by-4s, one on top of the other. They are installed with the edges of the 2-by-4 flush with the faces of the jack studs. A single 2-by-4 can be substituted in a passage door with a short stud above running from the top of the single header to the top plate of the wall. This stud is called a cripple. Headers for exterior doors are constructed by sandwiching ½ inch plywood between two 2-by-6s. They are installed between the jack studs with the 6-inch face running up and down ½ inch above the jamb head.

Door Sill

Door sills are the foundations of door frame construction. They are typically made from 2-by lumber: 2-by-6 sills for 2-by-4 frame walls; 2-by-8 sills for 2-by-6 frame walls. The sill is attached to the sill plate of the wall with either nails or screws. The sill sits below the threshold, with the jambs resting on top.

Door Jambs

The door jamb is the inside frame that directly surrounds the door. Most doors today are installed hinged into a pre-hung jamb. The jambs are the vertical side pieces of the inside frame. A small flat molding attached in the middle of the jamb is known as the door stop and does as its name suggests.

The tops of the jambs are attached to each other with a header that is usually notched into the side jambs. The jamb is spaced off of the jack studs with cedar shims and nailed or screwed to them for support. The jamb header is likewise screwed to the frame header.

Door Threshold

The seal at the bottom of an exterior is called the threshold, or door saddle. Thresholds, like sills, are not typically installed on interior passage doors. The threshold is generally the same width as the door jamb frame and ranges from 1 to 2 inches. The threshold is attached to the sill with screws. In a pre-hung jamb, the threshold comes attached to the bottoms of the two side jambs. The top of the threshold usually houses a vinyl weatherstrip that covers the installation screws when installed. The bottom of the door seals to keep out the weather.

References

• Finish a Basement: Door Framing
• Building Door and Entryways: Craig Weis, Sterling Pub, 1996