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Installing Interior Doors

Interior Door

Repairing, repainting or restaining your old interior door may still fall short of your decorative standards. Should this be the case, simply replace it. Learn what's involved in installing or replacing an interior door.

Tools & Materials

Use this checklist when you go to the store and purchase your items.


Considerations for Interior Door Replacement

When you replace a door, the preliminary work has already been done for you. There's already a hole where you need it. You can install the new door in one of two ways:

  1. If the existing jambs are ruined, out of plumb or just plain ugly, install a prehung door unit, which comes attached to its jambs with the hinges already in place. If the door is properly sized for your door opening, all you'll have to do is square the assembly with shims and nail it into place.
  2. If the door jambs are in good shape and the door itself is all that needs to be replaced, you can purchase a door blank or slab to replace the one you're removing. This is just the door itself with no associated trim; sized to fit into the existing door jambs. The doorframe, jambs and existing trim remain intact. This may seem like the easiest option, but unless you have finish carpentry experience, it's actually easier to install a prehung door unit. Installing only the door requires you to locate and mortise slots for hinges and bore knob and latch holes to align with the existing strike plate.

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Interior Door Materials

There are four basic types of doors: hollow-core, solid-core, solid wood and medium-density fiberboard (MDF).

Hollow-core doors are a popular option for many do-it-yourselfers. These are priced for the budget-conscious and are light and easy to handle. They come with either smooth or molded surfaces. Smooth doors have a stain-grade veneer of import hardwood plywood, oak or birch, so you can stain or paint it to match your decor. The surface of a hollow-core molded door is made of hardboard molded into a multipanel design. The most popular style is the traditional six-panel, but other classic styles are also available. Hardboard is a durable material that resists shrinking and swelling. The paintable surface has a wood texture, providing the look of wood-paneled doors for a budget price.

Solid-core interior doors look and feel like solid wood doors, but they feature a wood fiber core. These offer greater sound-deafening properties than hollow core doors and can withstand rougher treatment. Although not classified as fire doors, they also offer extra fire protection. The solid-core door offers the style and properties of a wood door without the cost.

Solid-wood panel doors can be stained or painted for a rich finish. Solid wood has natural sound-deadening qualities that keep the noise in or out. The properties that give wood its character may determine if these doors are an option in your home. These are heavy and you may need an extra hand to install them, but the weight gives solid wood doors a stable feel. Wood swells and shrinks over time and with humidity changes, so more precision is required during installation. Oak and white pine doors are very popular, but other types of wood are available through special order.

MDF is a waste-wood product that's made with fine wood fiber. The product is environmentally friendly, durable, easy to paint and is easily milled with power tools.



Installing a Prehung Door

Door installation can be fast and easy if the rough opening is properly measured and framed. When replacing an existing door, the rough door opening should be two inches wider and one inch taller than the finished door dimensions, unless otherwise specified by the door manufacturer. This extra spacing allows you to adjust and plumb your new prehung door assembly in case the opening isn't square. Once the door is properly installed, the gap around the edges within the jambs at the top and sides will be equal. The door should swing into the room against the nearest wall and take up as little living space as possible. Closet doors are an exception: They should swing outward to maximize closet space.

Since plaster and drywall have different thicknesses, different jamb widths are required. Measure the wall's finished thickness before purchasing a door. Prehung doors may come either with split or flat jambs.


Prehung Doors With Split Jambs

Remove all packaging materials, blocks and nails from your door assembly and separate the jambs.


Step 1

Place the closed door in the rough opening and center it. Use a level on the hinge side of the casing to align it vertically. Tap shims into place between the door jamb and the rough framing to make the jamb plumb.


Step 2

To hold the door in place, nail through both the jamb and shims into the wall stud near the top hinge using an 8d finish nail. Any nails that you drive through the jambs should also go through shims behind the jamb. This is necessary to prevent distortion of the jamb in the nailed area, which could cause the jamb to bow outward at the nails.


Step 3

Do the same for the other hinges.


Step 4

Check the door's alignment with a level again before continuing around the door jamb, installing shims and nails in the same manner. The space between the jamb and door should be the same for the entire length of the unit.


Step 5

With a saw, trim any shims that protrude from between the jambs and framing to allow the second jamb to be installed. Be careful to avoid damaging the jamb or wall. Slide the second jamb and casing unit in place against the first.


Step 6

Nail through the center of the stop and jamb to secure the second jamb. Align the nails with the ones you installed in the earlier steps to ensure that the nails will go through the shims as well.


Step 7

Nail the casings to the wall at 16-inch intervals with 4d nails. Use a nail set to recess the nail heads.


Step 8

Install the doorknob. The holes for the knob and latch assemblies should already be cut for you.



Prehung Doors With Flat Jambs

Remove braces and nails using a claw hammer.


Step 1

Place the closed door in the rough opening and center it. Use a level on the hinge side of the casing to align it vertically. Tap shims into place between the door jamb and the rough framing to make the jamb plumb.


Step 2

To hold the door in place, nail through both the jamb and the shims into the wall stud near the top hinge using an 8d finish nail. Any nails that you drive through the jambs should also go through shims behind the jamb. This is necessary to prevent distortion of the jamb in the nailed area, which could cause the jamb to bow outward at the nails.


Step 3

Do the same for the other hinges.


Step 4

Check the door's alignment with a level again before continuing around the door jamb, installing shims and nails in the same manner. The space between the jamb and door should be the same for the entire length of the unit.


Step 5

Trim any shims that protrude from between the jambs and framing to allow the door trim to be installed. Be careful to avoid damaging the jamb or wall.


Step 6

If necessary, miter the door casings and nail them in place. Nail every 16 inches using 4d finish nails. Set the nail heads.


Step 7

Install the doorknob. The holes for the knob and latch assemblies should already be cut for you.



Installing a New Door in an Existing Frame

If you've decided to replace only the door, not the jambs and trim, the most important job will be measuring. You must replace the old door with another of exactly the same size. (Unless, of course, the old door didn't fit well.) Keep in mind that this is a more difficult project than installing a prehung door, since the hinge relief mortises must be cut with precision. Installation of a doorknob is also more involved with this method.


Step 1

If the old door fit well, measure it down both sides and across the top and bottom. The door's corners should be close to square, but don't make that assumption. If the old door doesn't fit well, measure the opening across the top, bottom and along both sides.


Step 2

Draw a sketch of the door or opening on a piece of paper, and label each side with its corresponding measurement. Take this paper with you when you purchase your door so the sales associate can help you find a door that's the right size.


Step 3

It may be necessary to trim the new door to size. Also, if the door frame is out of square (if you get different values for corresponding measurements of the door or opening edges), it may be necessary to fine-tune the fit before installing the door. You'll have to do this at home.


Step 4

Remove the old door from the opening by unscrewing the hinges from the back edge of the door. Don't take them loose from the door jamb.


Step 5
Temporarily Support the Door on Wedges to Check for Fit

Check the fit of the new door in its frame by temporarily putting it in place and supporting it on wedges. There should be a clearance at the top and sides of about 1/16-in. The clearance below the door should be about 1/4-in, or a little more for doors that must swing over carpeted floors.



Step 6

If the door scrubs against the jambs in a place or two, or if the top of the door is out of line with the top of the opening, fine-tune the fit by shaving the door edges in those areas with a sharp plane. Bear in mind that wood expands in high humidity. You don't want a wooden door so tight in the frame that it will catch on rainy days.


Step 7

After the door is properly fitted and temporarily wedged in place in the frame, use a 4d nail or a quarter to maintain the right gap at the top. Transcribe the position of the hinges onto the door. Be careful, because the hinges must be placed exactly.


Step 8

From outside the door, while it's still in place and against the hinges, pencil a mark down each hinge where it meets the door face. By measuring the distance from this mark to the edge of the hinge leaf, you'll determine the width of the hinge relief mortise for each hinge.


Step 9

Remove the door.


Step 10

Using the marks you placed to align the hinges and the measurements of the hinge leaf, mark the location of the hinge relief mortises on the door edge.


Step 11

Remove one of the hinge leaves from the doorway by pulling the hinge pin. If the pin isn't removable, remove the entire hinge. Use your hinge or hinge leaf as a guide in the next several steps.


Step 12

Scribe along these lines with a sharp knife, and carefully remove the waste wood with a chisel to the depth of the hinge leaf. The hinge should be able to fit into the mortise so that its leaf is flush with the edge of the door.


Step 13

Again using your hinge leaf as a guide, mark the location of the pilot holes for the attachment screws in each of the relief mortises. Drill a 1/8-inch pilot hole for only the center screws of the top and bottom hinges.


Step 14

Reinstall the hinge or hinge leaf on the door frame.


Step 15

Shim the door in place at a right angle to the door frame. You may need a helper to do it. The door should fit right up against the hinges with the hinges recessed inside the hinge relief mortises, just as if the door were actually attached and open. Install the center screw only for the top and bottom hinges.


Step 16

Check the door operation. It should open and close smoothly. If the door strains against the hinges when closed, insert thin cardboard shims under the hinges and try again. When the door operates smoothly, install the rest of the hinge screws.


Step 17

Install the doorknob. This will require that you accurately locate and bore holes for the placement of the knob and latch assemblies.


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