How to Install a Pre-hung Entry Door
Updated: Dec 5, 2022
Want your home to make a good first impression? Start with the entryway. Replacing an old, leaky exterior door with a modern pre-hung entryway upgrade can give your home a fresh look and increase its energy-efficiency.
Removing the Old Door
To take off the old door, start by disassembling the lockset then removing the hinge pins (starting at the bottom). Lift the door out of place, then pry off the old trim. To remove the old jamb, cut through any nails or screws by running a reciprocating saw blade between the jamb and the house framing.
The rough opening needs to be around 1 to 2 inches wider than the door you are going to install, allowing room for adjustment and shims. Clear the rough opening of any broken fasteners, insulation or old caulk. (If the rough opening is too large, you can add boards to the framing.)
Installing the New Door
Fitting the new door in place is usually a two-person job, because one installer needs to be on the outside and the other inside to make adjustments. First, remove any cardboard packing or nails that hold the new door to the pre-hung jamb. Do not, however, remove the plug that connects the latch to the jamb, because this keeps the door closed during installation to keep the jamb in its rigid, rectangular shape. (Note: Most doors available from home centers are "pre-hung," which means the door comes attached to a door jamb designed to create a tight weather seal around the opening.)
Place the door/jamb combo in the rough opening by tilting or sliding it into position. Make sure the hinge side of the door is perfectly vertical. When you have it lined up and have determined no major problems with the fit, apply caulk/sealant beneath the door seal. Reposition the door along the hinge side and fix it in place by tightly placing shims around the frame to hold its position. (Note: If the entry door is exposed to rain, add a sill pan or extra flashing beneath it to protect the subfloor from water damage.)
With the door in place, start at the top and measure carefully with the level. You can fill gaps between the door jamb and the rough opening using wood shims. A shim is a tapered wedge used for making slight adjustments to door frames and windows, to make them plumb and level. When the shim and the frame are correctly positioned, drive a screw through the jamb into the frame to hold it in place.
Repeat the process around the door frame, inserting more shims to hold it securely while checking for level and plumb as you go. This may require a lot of readjustments, but take your time and do it right.
Once the frame is held firmly, open and close the door to make sure everything fits. Inspect the top of the door to make sure it closes correctly with no gap. If you find errors, go back and make adjustments. You might need to add more shims on the latch side of the jamb to help the door align correctly. Make adjustments until the door closes properly and the gap at the top is even, then fasten through the shims into the stud framing. To give the hinges extra strength, you can place shims behind them and hold them in place with longer hinge screws driven into the studs.
When the door is fully installed, it’s a good idea to apply expanding foam in the gap between the jamb and the rough opening. Be sure to use a low-expanding formula specifically designated for doors and windows.
Finally, install your trim package of choice and seal all seams with a flexible, paintable, weather-proof caulk. Prime and paint the trim, install your doorknob or handle-set, then the job is done.
Getting the new door to fit perfectly square and plumb can be a challenge, especially for inexperienced installers. Here are a few pro tips to help get the door to fit.
Gap Too Tight on the Side?
If a bowed jamb above the top hinge creates a gap that’s too tight on the strike side, drive shims between the framing and the hinge side of the head jamb until the gap is equal all around. (A bowed jamb is more common on the hinge side, but you also can use this trick to adjust the opposite side.)
Gap Too Tight at the Top?
If the gap above the door is too tight on one side, then insert a flat bar beneath the jamb on the tight side. Raise the jamb until the gap is even, then fasten in place.
Door Sill Not Level?
In older houses, you might find the door sill is not level. If the height difference between the two sides of the door is significant, the door won’t open and close correctly. Use a level to see if the floor is flat. If it’s not level, insert shims beneath the level until the bubble centers in the vial.
When the bubble reads level, measure the gap between the level and the floor. Use a hand saw (or circular saw with fine-toothed blade) to trim that measurement off one side of the door jamb so the pre-hung door will have an exact fit within the rough opening. Be careful—the side that will be on the higher side of the sill is the side that needs to be shortened.
Brick Molding in the Way?
Pre-hung doors commonly include pre-attached brick molding, which is wood trim surrounding the jamb to conceal gaps. The molding, however, interferes with insertion of adjustable wedge-shaped wood shims from both sides of the door (as they were designed to be used). You might prefer to pry off the brick molding, install the door with shims, then reinstall the molding.
The photos show a recent door installation in Alabama, where Jeff Winkle and his Highland Properties crew found that the molding interfered with the painted brick surrounding
the rough opening. Their solution was to remove the molding, rip it to a narrower size, then reattach it. Once the door was installed, caulked and painted, the alteration to the
brick molding became invisible.
Editor's Note: You can reach Jeff Winkle and Highland Properties at (205) 281-4125. Special thanks to the homeowners Paula and Michael Laney for help with this article.
Door Installation Aids
The AirShim is a contractor-grade inflatable air wedge for door, window and cabinet installations. It’s designed to replace damaging pry bars and temporary wood shims. It allows a single installer to position and hold items in place, saving jobsite time and labor costs by providing a much-needed extra hand in installations. It's perfect for window and door installations, and for positioning appliances and equipment. Use it anywhere you need to lift and align objects. The AirShim is certified for a 300-lb. load rating and has an internal stiffener with a rounded corner so it fits into tight 3/32-in. gaps without folding. When inflated, its 2-1/2-in. gap-spanning capacity means greater lifting or pushing range and more versatility on the job or around the house. Visit www.calculated.com.
TopStar Fastening System
Available from U2 Fasteners, the TopStar Fastening System utilizes an ingenious two-piece “screw within a screw” to reduce labor for the plumb installation of door and window frames (jambs) and built-in cabinets. When locked, the Top Star screw gets driven into the material, and when unlocked, the fastener’s inner screw turns independently from the outer portion for easy adjustment without shims.
First, drill a 5/16-in. pilot hole in the jamb then use U2’s Crown bit to drive the Top Star through the door frame and into the rough-opening until flush with the jamb. Then, slide off the crown to reveal the inner star bit and use it to adjust the Top Star’s inner screw, which moves the jamb in and out of the opening until plumb. This system is designed to make door installation faster than using wood shims to make fine adjustments. When installed with the Top Star system, if a door goes out of plumb over the years, use the Top Star screw to adjust it back to plumb position. Visit www.u2fasteners.com.