Exterior Door Frame Construction Specs

Wall Thickness

• The standard factory-built door frame is designed to fit inside the standard outside wall. With a measurement of 4 1/2 inches in thickness, the door frame fits perfectly into the common home. Any more than that and the builder must special order doors to fit properly. The 4 1/2 inches is derived from the 4 inches of thickness the building structure has used (typical 2-by-4-inch board construction.) One-half inch represents the thickness of the drywall board used to line the inner walls of the home. If the walls are not built to these specifications, then the door frame will not fit.

Materials

• Use of specific 10d nails are required, according to Handy American, for nailing down the door frame to the framework of the house. In addition, several tools are needed for specific jobs, like a hammer or nail gun, tape measure, saw and a pencil for markings.

King Studs and Headers

• A header is the extra wood that fills in the area between two king studs and above the door frame. The header rests on jack studs at each end. The jack studs and king studs when nailed together provide extra thickness and added stability for the door. The header is made with two 2-by-10-inch planks sandwiching 1/2-inch plywood to match the width of the 2-by-4 studs. The actual measurements for a 2-by-4 are 1 1/2 inches thick by 3 1/2 inches wide.

Natural Elements

• It is wise to consider local weather conditions before installing a frame. In an area that receives heavy amounts of rain annually, pressure-treated lumber is a better choice. Not only does the chemical layer of the wood resist rotting, it also wards off some common insects. Moisture in between the framework can lead to mold and mildew -- a bacterial growth that is fatal to some people when inhaled through the walls. Cypress and cedar are two common woods that resist moisture absorption, necessary in high humidity areas.