How to Make a Frame for a Slab Door

Measure the door opening from side to side at the top, middle and bottom. The sides will be wall studs. Because houses are rarely at perfect right angles, measure in more than one location. Use the smallest measurement for your frame width. Similarly, measure the door height from header beam to floor on the left, right and in the middle. Use the smallest of these measurements for your frame height. Now measure the wall thickness. Standard wall thicknesses are 4 9/16 inches or 6 9/16 inches, including ½-inch drywall on each side. Getting these measurements right is extremely important. Measure everything at least twice.

Buy two wooden side doorjamb boards the same width as the opening thickness and ¾-inch thick. They will be about 82 inches long and have a pre-cut notch, or dado, in the top to accommodate the top frame board. Saw them to the door height measurement.

Buy a wooden top frame board that's ¾-inch thick and the same width as the jamb boards. Saw it to the door frame width minus the thickness of the doorjambs at the top dado cuts.

Buy a slab door with a width equal to the width of the door opening minus 1¾ inches to allow for the width of the doorjambs plus 1/8 inch on each side of the slab door. The slab door height should be equal to the height of the opening minus 1 inch, allowing ¾ inch for the top frame board and 1/8-inch clearance at the top and bottom. You may have to cut a slab door to size to make it fit.

Set the door on its opening edge with the hinge edge up. Make a mark 5 inches from the top for the top edge of the top hinge. Make a mark 10 inches from the bottom for the bottom edge of the bottom hinge. Place a hinge with its top edge at the top mark and trace the outline of the hinge leaf. Place a hinge with its bottom edge at the bottom mark and trace its leaf outline.

Measure the thickness of a hinge leaf. Score the outline marks on the door to the same depth as the leaf thickness, using the utility knife. With a rubber mallet lightly tap a sharp wood chisel into each outline every ¼ inch along the edge of the door as deep as the hinge leaf thickness. Gently tap the chisel to remove the wood inside the outlines to create a flat recess for the hinge leaves. This is a delicate operation. The leaf recesses must be the exact size of the leaves and completely flat.

Place the leaves in the recesses and mark the screw holes. Remove the hinges and drill pilot holes slightly smaller than the hinge screws at the marks. Replace the hinges and screw them to the door.

Center the hinged side of the door with the hinge side doorjamb. Leave 1/8 inch between the dado cut at the top. Trace the free hinge leaves onto the doorjamb. Repeat steps 6 and 7 to attach the hinges to the doorjamb.

Seat the top board into the dado at the top of the hinged doorjamb. Attach it to the doorjamb with two or three 2-inch deck screws. Seat the other end of the top board in the dado cut in the free doorjamb and attach it with two or three more deck screws.

Cut two pieces of doorstop trim to the inside height of the door frame. Cut a third to the top inside width. Use a miter saw to cut the top corners of the long pieces and both corners of the small piece at 45-degree angles so they fit together snugly. With the doorjamb assembly lying on the floor with the door on the bottom, place the doorstop trim pieces along the sides and top of the frame on top of the door. Wedge small pieces of scrap cardboard between the door and the trim pieces. Nail the trim to the doorjamb with 1-inch brads. The door frame is ready to install in the opening.