Doors are built to last. However, there are times when an interior door in your home may need to be replaced i.e. if there has been some damage to the door or you would like to upgrade your home by replacing the doors with new doors for aesthetic or functional purposes.

Regardless of your choice of doors, there are some things that you need to know about interior door installation before you begin.

Time Required

custom interior door install by trim team

Replacing interior doors takes time and skill to ensure proper installation. You can expect a contractor to take anywhere from 20 minutes to an hour to install a pre-hung door, depending on whether the framing is correct and everything else is okay. If this is not the case, it may take longer. If you intend on doing the task yourself, give yourself ample time.


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Installing a pre-hung door can be a time-consuming task, particularly if you have never installed a door before. In fact, it can be frustrating for an experienced builder.


The cost to install a pre-hung door can vary dramatically depending on where the door is to be installed, the quality of the door and whether or not you are hiring a contractor for the job. However, it is safe to say that the average labour cost for installing an interior door can be anywhere from $150 to $300. This is in addition to the cost of the door.

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An interior door can cost anything from $60 to $200 based on the quality of the materials used. And that the determining factor is whether the door is hollow or solid core. The higher-priced doors tend to be of higher quality and durability so it’s necessary for you to weigh the pros and cons to assess what type of door you need.


Being able to install an interior door successfully depends on having the right tools to accomplish the task. To install your interior door, you will need:

interior doors installation by trim team
  • 18-volt ONE+ cordless AirStrike 18-Gauge Brad Nailer with sample nails
  • 16 oz raw claw hammer
  • 9 in. Torpedo Level
  • 15-inch contractor cedar shim
  • 12 in. Wonder Bar Pry Bar
  • Safety Glass Scraper with 5 Blades

What Is a Pre-hung Door?

Pre-hung doors come already attached to a door frame. This makes it easy for you to install the door and as long as you have an understanding of what you’re doing, you can do this relatively easily by following proper instructions. Slab doors I also are often commonly known as blank doors, require a little more work because they do not have any part of the door attached.

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Slab Doors are typically less expensive because you do much of the labour-intensive part yourself. While pre-hung doors cost more but are easier to install. So in choosing whether you would like a pre-hung door or a slab door, consider how much skill you have and whether you anticipate any issues that require expertise. This can involve damage to the door that may make removing it and installing a new one more complicated.

Common Mistakes to Avoid When Ordering Pre-hung Doors

Pre-hung doors are designed to create an easy installation process. However, there are a number of mistakes you should avoid making.

Taking Wrong Measurements

Measurements for installing interior doors

This can be a very expensive error to make. That’s why it’s always important whenever you are doing home improvement projects to double-check your measurements, always. You need to purchase pre-hung doors that will actually fit into the space and if your measurements are off by just a little, you can find yourself with a door that does not open or close properly. We always advise buying pre-hung doors that are smaller, this way you can fill in the gaps by extending the jamb – much simpler to do than widening your doorframe.

Foregoing Shims on Pre-Hung Doors

photo of wood Shims for interior door installation

This is a common error that people make. Simply because they may not be familiar with how to use shims. Shims make all the difference when installing an interior door and ensures that the door fits into the larger frame and fills any gaps. If you notice gaps that are larger than a quarter of an inch anywhere around your door, nail the shims in place.

Not Locating the Studs

interior door install by trim team

it’s possible to install a pre-hung door without screwing into the studs, however, this may cause the door jambs to warp or pull away over time. When you use a stud finder to locate the studs, you can locate them easily. They should be located 12 to 16 inches apart.

How to install an Interior Door (step by step tutorial)

Determine Your Door’s Handedness

trim team installed interior door

First, inspect the old one and the new one to make sure that the “handedness” matches. This is very important because it will affect the look and efficiency of your door. Stand in the doorframe and put your back along the hinges. Check to see what side the door knob is. If the hand of the door knob is on your right, that means it is a right-handed door. And if it’s on your left, it is a left-handed door.

Removing the Door

Just make sure that you have the appropriate tools to remove the door. You will need a screwdriver, hammer and a pry bar. When removing the existing door, be sure to exercise caution.

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  • Step 1: First, take off the hinge pins using a screwdriver and hammer.
  • Step 2: Remove the door from the door frame carefully.
  • Step 3: Remove the hinge plates and strike plate from the doorframe and loosen the trim using a putty knife.
  • Step 4: Use a pry bar to separate the trim but doing so carefully so as to avoid damaging the wall. This requires a lot of patience and care. Examine your trim and if it is in good condition, you can simply reuse it if you are installing a prehung door and a one-piece jamb door. A two-piece chapter already comes with the trim attached to it.
  • Step 5: Pull the side jambs away from the studs and then do the same for the head jamb.

Thinking of painting? If so this is the best time to do so. Perform repairs or touchup work on the wall if necessary. Whatever changes need to be to the wall or doorframe need to be done before installing a prehung door. Remember to be careful and take your time to avoid damaging the wall during the installation process.

Positioning the Prehung Door

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With the old door removed, the next step is to align the new door and so that it fits perfectly within the door frame. To do this, slide the prehung door into place and place it in the opening, sliding in until the jamb fits nicely within the door. Make sure that the door opens the way it should. It’s important to note that prehung doors tend to be heavy, so it’s best to have someone close by to assist you as needed.

Add Shims

One important thing about the door is to make sure that it is straight. You can use a level to do this and add shims to adjust the level and make sure that the jamb is aligned correctly. The door frame is a little smaller than the opening, which makes adjustment possible. Slide the shims under the side jamb until they are level with the head jam. Fill in the sides using the shim to fill in the side jams and the studs to fill in any space between them.

photo of wood Shims for door installation

At the hinge, beginning from the bottom and making your way to the top of the jamb, shim between the hinges and the studs, making sure to position the shim so that approximately half of the shim is above the hinge. This will be helpful when it comes to nailing. Look for the side where the latch is on and shim at the same places and at the latch level. Then reassess the level of the door.

Nail Door Frame to Studs

custom interior door installation

To do this, drive two #8 finishing nails through the frame, shims and into the studs. Do this about an inch from each edge of the jamb, and about 1 1/2 inches above each other. Be sure to open and close the door and check to see that there are no issues. If there are, make the necessary adjustments before driving the nails all the way in.

Installing Door Trim

Once you have nailed the trim to the jamb and stubs, you need to drive #6 finishing nails through the trim and into the studs that are behind the wall, being sure to space the nails approximately 16 inches apart. If there are any shims that are overlapping or exposed, be sure to trim them with a knife, breaking them along the line.

modern interior door by trim team

Next, cut and install the trim on the second side of the door the same way you did on the first side. Once the door is hung, the next step is to attach the back plates and door knobs. Ensure that the knobs are screwed on tightly securely but not too tightly. And you’re done!