Measure the door opening to determine the size of the door needed. Do not forget to measure the depth of the door in addition to height and width. Doors do come in different thicknesses, and the door must be correct in thickness to provide a good, energy-efficient seal. Get a door that is a half-inch shorter than the height and three-quarters of an inch narrower than the rough opening for the best height and width fit.
Establish which way you want the door to open. Stand at the opening with your back to where the hinges will go and picture opening the door from both sides of the opening. Select either a left- or right-hand opening door.
Stand the door into the prepared opening to check the fit. Make sure the door will clear the finished floor, measuring from the bottom of the sill to the bottom of the door. Measure the thickness of the flooring and compare the two measurements to see if the door will clear. If it will not, install a piece of treated wood thick enough to raise the door so it will clear and screw it into place.
Cut a pressure-treated two by six sub-sill using the skill saw. Check it for square and level. Use shims as needed to bring it to level, then screw it into place using a screw gun and galvanized screws.
Apply a bead of sealant the entire length and width of the sub-sill. Apply the same sealant to the sill of the pre-hung frame. Stand the pre-hung door into the opening from the outside and down onto the sill. Shim the door from the top to hold it in place. Use a level to adjust the door frame to plum and square.
Insert shims at the hinges, continuing to check for plum and square. Make sure there is clearance of one-eighth inch between the pre-hung assembly and the rough opening. Screw the hinges into the shims. Look to make sure there is an even gap at the door.
Things You Will Need
- Tape measure
- New pre-hung door
- Installation diagrams/instructions
- Work gloves
- Safety glasses
- Cordless screwdriver
- Skill saw
- Pry bar
- Caulk---to weatherproof the door
- Open and close the door, making any needed adjustments before adding trim and hardware.