California building code dictates that any entry door connecting a garage to a house must be fire-rated. The minimum rating is 20 minutes, meaning the door can withstand and prevent heat and fire from breaching through the door for that long. Fire-rated doors come pre-hung, meaning the door, sill, jambs and brick molding come as a pre-assembled unit. A fire-rated door may be made of steel or wood, but either way, they are very heavy, so having a person assist you in lifting and positioning the door is helpful.
Measure the rough opening in the wall framing to ensure it is large enough for the height, width and depth dimensions required to install the door. These dimensions are printed in the instructions that came with the door.
Place multiple beads of polyurethane caulk under the door sill or on top of the framing on which the door sill will sit. Place a bead of polyurethane caulk along the back side of the brick molding.
Lift the door into position from the outside, and place it in the rough opening. Push the door so that the brick molding is flat against the garage-side wall.
Pre-drill 1/8-inch holes through the hinge-side jambs near each hinge. Place the level along the hinge-side jamb to check that it is plumb left to right as well as forward and backward while facing the door. Drive a 3-inch screw through each pre-drilled hole and into the wall framing. Do not tighten the screws all the way.
Place tapered shims immediately above and below the screws. Adjust the shims in or out to take up the slack between the jamb and the wall as necessary, while ensuring the jamb is perfectly plumb. Tighten the screws. The screw heads should be slightly below the surface of the jamb. Trim the excess material from the shims by first scoring the shim with a utility knife, then snapping the excess off at the scored line.
Pre-drill holes in the latch-side jamb in the approximate locations as you did on the hinge-side jamb. Check the jamb for plumb as you did on the hinge side. Measure from the top left corner of the door frame to the bottom right corner. Then measure from the top right corner to the bottom left corner. These two measurements should be exactly the same for the door to be square.
Screw 3-inch exterior screws through the pre-drilled holes into the wall framing, but do not screw them in completely. Install tapered shims as necessary to fill the void between the jamb and the wall framing, then screw the screws in completely. The screw heads should be slightly below the surface of the jamb.
Remove the transport or shipping latch from the latch pocket. Install the door handle, latch kit and deadbolt, if provided, according to the manufacturer's instructions. Open the door and check that it closes completely on its own and latches shut, as it should due to the self-closing latches. If the door does not latch shut on its own, adjust the spring tension in the latches according to the manufacturer's instructions. There are several styles, so adjustment techniques may vary.
Shoot finishing nails through the brick molding with a nail gun, then apply polyurethane caulk around the edge where the brick molding meets the garage wall. Spray fire-rated expanding foam to fill the cavity between the door jamb and the wall framing. Do this from inside the house. When the foam has fully cured, trim away the excess with a utility knife so the foam is flush with the edge of the jamb.
Measure and cut interior trim to cover the gap between the edge of the jambs and the interior walls of the house. Cut the molding with a miter saw and install the trim with finishing nails.
Apply paintable, stainable wood putty to cover the screw heads in the jambs. Sand the putty flush when it is dry, then paint or stain to match the rest of the jamb.