Installing a Prehung Entry Door
by Lee Wyatt
(last updated December 30, 2013)
Prehung entry doors are becoming more and more popular a choice among homeowners as a means to increase their home energy efficiency. Installing a prehung entry door may seem like a lot of work at first, but all it really takes is about three hours of time for even the most novice of DIYer's. Here are some simple instructions that you can use to help ensure that you are installing a prehung entry door the right way, the first time.
- Tin snips
- Carpenter's level
- Pry bar
- Circular saw
- Caulking gun
- Wood chisel
- Drip edge
- Casing nails
- Wood shims
- Silicone caulking
- Prepare the opening. It may be necessary to prepare the opening for your new door. This would entail that you remove the old door, and ensure that the opening will be the same size as your new door. As you are removing the old door, make sure that you also remove the old door frame, since the new prehung door comes with frame already attached.
- Test fit the door. Place the new door into the rough opening, and see if it will fit into the rough space. Use a level to help ensure that the door is plumb. If necessary, you may need to apply a few shims to the lower side of the door jamb to make everything plumb. Make any adjustments that are necessary to ensure that the doorjambs are square with each other, and then double check to make sure that the door is centered.
- Trace the molding outline. Along the outside frame of your new doorframe, take a pencil and trace the molding. If you have any vinyl or metal siding, make sure that you make the outline a little larger to allow for the extra trim that will be required.
- Cut along the outline. Remove the door from rough opening, and plug the circular saw into the outlet. Make sure that you have your safety glasses on, and then begin to cut into the siding following the outline. Make sure that you have the depth set on your circular saw to the same thickness as the siding that you have on your home. You do not want to cut any deeper than that. As you are cutting the outline out, make sure that you do not cut into any sheathing, and that you do not cut into any corners. Rather, finish just short of the corners, and then finish the corners by using a wood chisel.
- Make a temporary door. Make an temporary door by placing a piece of drip edge into the siding at the top of the opening. Do not nail the drip edge. This will help prevent any creepy crawlies, and excessive moisture from getting into your home.
- Double check the opening. Double check the opening for your door, and if necessary enlarge it to fit your door. Once again, remove the door from the opening, and apply some caulking to the bottom of the doorsill. Make sure that you use enough caulking by applying several beads, and that you are also caulking underneath where the jamb and molding will be.
- Center and plumb the door. Reinstall the door, and make sure everything is centered and plumb. Check to make sure that the doorjamb is plumb along the hinge side of the door using a level. Screw the hinge jamb in place, temporarily, by driving two #8 3-inch drywall screws through it. The first one should be about two inches above the hinge, and the other two inches from the center hinge. Recheck to make sure everything is still plumb, and if necessary loosen the screws a little to become plumb again.
- Shim the interior of the door. Go inside your home, using another door, and insert some shims into the gaps behind hinges, and between the jamb and framing. This will help stabilize the door while you are working. To get the tightest fit, take two wedge shaped shims, and place them together to form one on flat shim. Use cedar since it is more weather resistant than other woods.
- Remove brackets and some of the screws. Remove the retaining brackets that are still on the door, and then test to see if the door will open and close properly. Once it does, go ahead and open the doorway and remove two of the screws from the top hinge. Replace these screws with long anchor screws. These anchor screws should have come with the doorway, but if not then only purchase screws that are the length recommended by the manufacturer. Otherwise, you may end up causing unnecessary damage to the door.
- Anchor the molding. Anchor the molding to the framing members by using some 10d galvanized casing nails. Drive these nails every 12 inches around the door frame. Use a nail set to ensure that you drive the nail heads below the wood surface of the molding.
- If possible, adjust the threshold. Some doors will come with an adjustable threshold. If yours does, adjust it as necessary according to the manufacturer's instructions to provide a tight seal.
- Cut the shims and apply caulking. Cut any shims so that they are flush with the door frame. When doing this, make sure that you use a utility knife to avoid any unnecessary damage. Fill any nail holes, and the exterior of the door frame with caulking to provide weather tight seal.
- Replace casing. Inside your home, replace the casing of the interior doorjamb. If the casing happened to get damaged during the removal, this would be the time to replace it with new casing.
- Install the door locks and strike plate. Install the door locks for you new door, as well as the strike plate. Congratulations, you are now finished with your project.
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