How to Install an Exterior Prehung Door
Level
Square
Drift Pin
Hammer
Flat Bar
Reciprocating Saw (optional)
Hacksaw (optional)
Drywall Screws
Caulk
Phillips Screw Driver or Drill motor & Phillips Bit
Lockset
Shims
Window & Door Foam Insulation
First you have to decide the type and style of your new door. You have a choice of fiberglass, steel or a wood door. Steel doors and fiberglass are the most popular because of their thermo effeciency and they also have the largest selection of styles. You will have to visit a home improvement center to pick the style of door you want. You will want to measure your door and check the swing prior to your trip to the home improvement center. Measure the width and height of your door between the jambs (frame) for the width and from the sill to the head jamb for the height. We are assuming your door swings in for the benefit of figuring the swing. If you are standing outside and the door knob is on the right side your door is a left hand (/) swing and if the door knob is on the left side
your door is a right hand (\) swing. While checking the swing measure the width of the door jamb (frame) so the new doors jamb will match.
When your new door arrives you are ready to install it, but first measure it and check the swing before you start removing the old door. If everything is all right you are ready to procceed.
1) Remove the casing from the inside and the brick molding or casing from the outside of the old door. Remove the old door from the frame by removing the hinge pins with a drift pin. When removing the hinge pins leave the door closed, this will make it a lot easier. Then just turn the knob open the door and pull it out and seperate the hinges (be ready because the door could be heavy) You are ready to remove the frame. You have two options: Run a
reciprocating saw with a metal cutting blade between the jamb and frame to cut off nails (some times a hacksaw will work). When all the nails have been cut, push the door out from the top and remove it from the rough openining. If you don’t have a reciprocating saw and a hacksaw won’t work you will have to use a flat bar and pry the jamb out.
2) After removing the frame check the old sill and see if it’s sitting on the subfloor or is an extention of the subfloor. If the sill is sitting on the subfloor remove it and set the new door on subfloor, if the sill is an extention of the subfloor you will have to set the new door on it. Before installing the new door on the old sill check and make sure it’s not rotten, if it is replace it with treated lumber matching the size. Before replacing the sill check and make sure the frame work under the sill is level, if not shim the treated sill to level. Make sure to put a good adhesive caulk under the sill before installing to keep water and cold air out. If the old sill is okay and not to high for the new door but not level (same for unlevel subfloor) you will have to level the sill (metal sill attached to door) of new door while installing . Make sure to use a good quaility caulk between the metal door sill and the subsill (old sill).Now you want to check and make sure the opening
is square (the house may have settled). If the frame is slightly out of square, you may have enough clearance between the door jamb and the frame to square the new door with shims.
If not, you may have to realign the trimmer stud or shave them down with a reciprocating saw or a chisel.
3) With a square opening, half the battle is won (leveling sill is very important). Some door units are very heavy, and must be moved and installed with care to ensure the door remains aligned in the frame. You’ll need an assistant to help you install the door. Set the new prehung door in the opening (don’t forget to caulk under the sill) and put a square on the upper corner on the hinge side and move door until the door’s corners are square.
When the hinge side is plumb (check with level) drive two 3″ drywall screws through the jamb, into trimmer studs, about 2″ below the top and center hinge to temporarily set the door. Shim the hinge jamb with pairs of tampered shims or wood shingles placed directly behind the hinges. Next shim the latch jamb in the same way. Before procceeding, notice there is one screw missing on each jamb size hinge. You will find (3) extra 3″ screws loose with the door, these are to secure the door frame (through empty hinge holes) to spinner studs. When the door is properly aligned, drive these screws through each set of shims.
Using 3″ drywall screws secure the lockside jamb through the shims (at three locations). Remove prehang clips and open and close door, checking that it swings easily and makes uniform contact with the weather strip. If it doesn’t, remove the appropriate screws and realign the door and then rescure. If the door isn’t making good contact with weather stripping check to make sure you are plumb inside to outside.
4) Fill gaps between jamb and studs with window and door foam insulation and caulk brick mold and where the jambs and threshold meet the sill. Find the two rectangular foam weather seals with adhesive on one side and place them at bottom of jamb (one on each jamb) just inside of the door weatherstrip. Install lockset and install inside casing. Some doors require special preparation before finishing, so check the manufacture’s instructions before you paint or stain your door.
