The biggest reason this is a simple operation is that these doors come prehung. What this means is the door is already hung in its jamb. The hinges are mortised into the door and jamb and screwed in place. The door is held in position by the hinge pins, leaving the perfect reveal around the door and the jambs top and sides. The holes are also bored for the lockset and if necessary, for the deadbolt too. Exterior doors come in wood, fiberglass, and the most popular, steel. The two sizes are normally used for exterior doors are 32″ and 36″. With the sizes of today’s furniture and appliances the smart choice is the 36″ door. The standard height for a door is 6’8″ but taller ones can be special ordered.
The exterior trim comes nailed to the jamb. This trim, called brickmoulding, is mitred and already installed, saving the installer(s) another step. These doors also have an aluminum threshold already attached to the legs of the jambs. All these things make the door and jamb one cohesive unit.
The standard jamb size is 4 and 1/2 inches wide. With the demand for a higher insulation R value in exterior walls, 2×6 framing is being used more frequently. Jambs to fit these walls, 6 1/2 inches, are becoming more common. Jamb widths can be made to order for whatever a projects needs are and would cost more.
To install an exterior door, first check to see if the rough opening is correct. The width of the opening should be 2″ wider than the door itself (38″ for a 36″ door, 34″ for a 32″ door). For a rough opening height 83″ will suffice for most door manufacturers. Also check to see if the framing and floor is reasonably plumb.
Door installation is easier with 2 people but can be done alone. Put the door in the opening from the outside. If you are working alone, tack the door to the wall through the brickmoulding, not driving the nails home. I like to use galvenized ring shank splitless nails that are used for cedar siding. They don’t split the wood and the smaller heads are not as obvious to the eye. The ring shank feature gives them great holding power.
With the door tacked in the opening, go to the inside of the door and check the reveals around the door. There should be about an eighth of an inch all around the door. Shim the jambs of the door so the reveals are right. Check the door jamb on the hinge side for plumb. If it is not plumb, then the floor is out of level. One jamb leg or the other will need to be shimmed so the threshold is level. Now readjust the reveals by moving the door and jambs sideways in the opening to a point where the reveals are right. Once the door and jamb are in position, shim the jamb at each hinge and at the strike, top and bottom on the strike side. Nail the shims in place by nailing through the jamb, through the shims and into the framing. Check the door swing to see if it opens and closes properly. If all is well, go outside and nail through the brickmould using the splitless nails to nail the door frame to the house.
Most door manufacturers provide long screws that replace some of the shorter screws in the hinges on the jamb. The top hinge is the most important place to use one or two of these screws.
These screws go through the jamb and into the framing and keep the door from sagging over time.
Most doors come with an adjustable threshold. This may have to be adjusted up or down to create an airtight seal.
With the door securely in the opening, it is ready for door hardware installation.