Installing Problem Free Prehung Doors

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Materials Needed:

  1. 1Tape Measure
  2. 2Framing Square
  3. 3Level
  4. 4Electric Drill / Screwdriver
  5. 51/8' Drill Bit
  6. 6Hammer
  7. 7Water Base Putty
  8. 8(17) 3' Installation Screws
  9. 9Quality Exterior Grade Caulk
  10. 10Hand Saw
  11. 11Router (recommended) or Chisel
  12. 12Wood Shims
  13. 138p Finish Nails
  14. 142 Galvanized Dry Wall Screws

About the Material

This product is extruded using the latest vinyl blended Composite Cellular PVC Technology. The frame and material have been thoroughly tested for better stiffness than traditional 100% PVC foam profile, The PF Frame composite doorframe provides superior performance, with high durability and low maintenance, offering a Hydroshield feature compared to traditional PVC or wood doorframes. The frame can be installed with standard carpenter tools.

Prepare the opening

All I here is it’s harder for a carpenter to install doors after floors are installed. It’s human nature to seek the easier softer way, but it only makes common sense that you install floors first then have a skilled carpenter to put door frames on top of floor, then trim around door last. Cover floor for protection where needed. I'm replacing an interior door - including the original jamb - in my house with a new 30' pre-hung door. With the jambs, the new door is 31 3/8' wide. However, the original rough opening is between 32 1/2' and 32 3/4' wide, leaving me a big gap between the old frame and new jambs. Some exterior pre-hung doors come with brick molding already attached. Depending on the fit of the jamb to the frame, it may be necessary to remove this molding. Should this be necessary or desirable, place a small block of wood on the back side of the molding and tap lightly with hammer working around door until molding comes off. Hanging interior prehung doors can be somewhat challenging. Don't underestimate the complexity of the job by any means. Fortunately, though, it requires a few simple tools and a minimum of.

Always prepare the opening before you attempt to set the jamb.

Before you attempt to set a jamb make sure the rough opening is square, plumb, and in the same plane. Any issues left uncorrected will become bigger problems later.

Correct Cross Leg
If you set a jamb into an opening with cross-legged walls, the door won’t lay flat against the jamb and the door stop. You might even think the door is warped, when it isn’t. There are two ways to check for cross-legged walls.

Drive a nail or screw into each corner of the rough opening, then run a string around the four screws, creating an X at the middle of the doorway (Fig.1).

The two strings should touch each other at the X (Fig.2). If they don’t, try to move the walls at the bottom of the opening—just a little. Use a small sledge hammer and a block of wood and tap the bottom of each wall lightly. You want to move each wall a little at a time until the strings touch or are close to touching. Don’t worry about getting it all. You can correct crosslegged walls when you set the jamb, too.

You can also check for cross-legged walls by cross sighting a jamb. If the jamb isn’t in a narrow hallway, stand to one side of the rough opening and sight across the edge of the jamb nearest you to the opposite edge of the jamb farthest from you (Fig.3). You’ll need to move your head in order to sight along both edges. Once your head is positioned, look up and down the edge of the nearest jamb. The edge of the farthest jamb should remain parallel. If it doesn’t, the walls are cross-legged; you can see how much the walls must be moved in order to correct the condition.

  1. Level the floor
    Don’t wait until the jamb is in the opening to level the floor. Instead, place a level on the floor and shim it until it is level (Fig.4). If you’re installing the door on a finished floor—like stone, tile, or hardwood, you can measure the thickness of the shim and cut that amount off the opposite leg. If the flooring isn’t installed, leave the shim in place and set the jamb on top of it.

  2. Shim the rough opening
    Most rough openings are framed too big and must be shimmed in before setting the jamb, otherwise piles of shims must be inserted between the jamb and the framing. Use plywood squares to shim in the rough opening so that the ‘corrected’ rough opening is 1/8” wider than the outside dimensions of the door.

  3. If the door is in a hallway or other critical location, be sure to center the corrected rough opening, so that casing and drywall reveals will be equal on both sides of the finished door.

  4. DO NOT SHIM BEHIND THE HINGES.Shimming behind the hinges before setting the jamb will prohibit you from making critical adjustments to hinge gaps and will prevent you from making necessary adjustments to strike gaps.

Pin the door in the opening

Place the jamb in the opening, and then remove the fastening screws or temporary latch. Insert two shims at the top of the jamb on opposite side of the head jamb. These two shims will safely secure the jamb and the door in the opening (Fig.5). Adjust the top of the jamb so that it is flush with both sides of the wall—or as close as flush as possible, so that installing the mitered casing will be easier (Fig.6).

The first five fasteners

Install the first five fasteners in precisely the correct locations and in exactly the right order. Otherwise, you may not be able to adjust the door properly.
*Note: In this instructional example, we are driving screws through pre-drilled, counter-sunk holes in the face of the jamb. Instead, drive 15ga finish nails at each location, or drive screws close to the shoulder of the lower rabbet, where the kerf-in weatherstripping will hide the screws.

Fastener #1
Drive Fastener #1 up near the top of the hinge jamb—as high on the jamb as possible (Fig.7). Do not shim behind Fastener #1. Shims are already installed at the top of the jamb.

Fastener #2
Drive Fastener #2 up near the top of the strike jamb—as high on the jamb as possible (Fig.8). Do no shim behind Fastner #2. Shims are already installed at the top of the jamb.

Fastener #3
Fastener #3 must be driven at the very bottom of the hinge jamb, as close to the floor as possible (Fig9). But before driving Fastener #3, correct any remaining cross-leg. Move the bottom of the hinge jamb in or out of the wall until the door is lying flat against the strike jamb. If the jamb is severely cross-legged, don’t try to correct it entirely on the hinge jamb—you can still correct cross-leg before driving Fastener #4 (this is especially important with pairs of doors). You may need to insert an additional shim to back up the jamb before driving Fastener #3 .

Fastener #4
Fastener #4 must be driven at the very bottom of the strike jamb, as close to the floor as possible (Fig.10). But before driving Fastener #4, correct any remaining cross-leg. Move the bottom of the strike jamb in or out of the wall until the door is lying perfectly flat against the strike jamb. If you’re installing a pair of doors, be sure that both doors are flush from the top to the bottom before driving Fastener #4.

In order to maintain a consistent and acceptable strike gap approximately 1/8”, you may need to insert an additional shim to back up the jamb before driving Fastener #4.

Prehung Exterior Doors

Fastener #5
Fastener #5 corrects a serious issue with pre-fit doors—especially heavy pre-fit doors. The weight of a door will pull down on the top hinge, placing the top hinge under tension. That tension will increase the hinge gap above the top hinge (Fig.11). If the hinge gap above the top hinge is not corrected, it maybe not be possible to correct the strike gap and the door may rub against the strike jamb.

To relieve the tension on the top hinge and jamb, replace one of the top hinge screws with a screw long enough to penetrate the jamb and the wall framing (Fig.12).

To relieve the tension on the top hinge and jamb, replace one of the top hinge screws with a screw long enough to penetrate the jamb and the wall framing (Fig.12). Do not torque this screw too much or the door will be jamb bound. A slight amount of pressure on that screw will correct the top hinge gap (Fig.13). And in the future, that screw can be loosened or tightened to correct the fit of the door in the event the home settles.

Support the hinge jamb

Insert pairs of shims—one from each direction—above and below each hinge, and every 12” on center (o.c.). Drive fasteners below the shims, not through the shims. The shims may have to be adjusted in order to improve the fit of the door (Fig.16).

Shim the strike side and head

Insert shims every 12”. o.c. behind the strike jamb, and shim behind the lockset and dead bolt locations, too (Fig.17). Drive fasteners below the shims, not through the shims. Do not drive fasteners near the lockset or deadbolt locations.

Shim the head jamb so that the head gap is even across the top of the door.

Q. I want to save some money on an upcoming project. It seems to me that I could successfully hang interior prehung doors if I had some guidance. Surely it can't be that hard to do. Of course I want the doors to operate smoothly from now on. What must I do to get trouble-free door operation?

A. Hanging interior prehung doors can be somewhat challenging. Don't underestimate the complexity of the job by any means.

Installing Problem Free Prehung Doors

Fortunately, though, it requires a few simple tools and a minimum of materials. You'll need a 2-foot level, a 4-foot level, a hammer, a nail set, a screw gun, a small square, a bundle of wood shims, a pound of 8-penny finish nails and several 3-inch-long drywall screws.

With prehung interior doors, much of the work is already done for you. But there are still steps you must take to get a perfect fit.

Typically the manufacturer will leave some extra length on each of the side jambs. This is done so you can adjust for a floor that is out of level across the width of the door opening. Checking the floor is the first thing you'll want to do.

You do this with a 2-foot level. If the floor is out of level across the opening, one of the jamb legs, the one on the high side of the opening, will need to be shortened. If you fail to make this adjustment in length, one of the jamb legs will end up floating in the air as you begin to secure the jambs to the rough opening.

The door slab itself is almost always perfectly square. The trick is to adjust and support the jamb in the rough opening so that the spacing between the jambs and the door is consistent all the way around the door.

You start the job on the hinge jamb. Use the 4-foot level to check the hinge-side rough opening to see if it is plumb. If it is out of plumb, try to measure how much and where it is out of plumb. You will need to know this information so that you can insert the proper amount of shims between the jamb and the rough opening as you start to hang the door.

Position the door and the jamb in the rough opening, and use one or two 8-penny nails to temporarily tack the hinge jamb into place. Use the level and necessary shims to get the hinge jamb as plumb as possible.

Be sure that the doorjambs are flush with the finished wall surfaces on both sides of the wall. Ideally, you would like to see the jamb project beyond the finished wall surface by about 1/32 of an inch.

Slide shims as necessary between the jamb and the rough frame at each hinge location. Tack the door in place with additional nails and close the door.

Stand on a ladder and check the top of the door to see if the spacing between the door and jamb is equal across the entire width. It should be an 1/8-inch gap or so. You should have a similar gap on the hinge side. If the top gap is not consistent, you need to readjust the length of one of the side jambs.

Once the size of these gaps is the same, it's time to work on the latch or doorknob jamb. Simply slide shims between the jamb and the rough opening until the gap is consistent and the door operates smoothly. If you are satisfied, nail the jamb in place at the shim locations. The space between the shims should not exceed 24 inches if possible.

How To Install A Not Prehung Door

The key to years of trouble-free service is to screw the hinge jamb to the rough opening. Without screws, repeated operations can cause the door to sag slightly.

I prefer to hide the screws behind the hinges. To do this, remove the screws from one hinge at a time on the doorjamb. Gently pry the hinge out of the jamb, and install a long drywall screw through the jamb into the solid wood of the rough opening. It's an old carpenter's trick I learned long ago.

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Prehung Exterior Doors With Glass

Write to Tim Carter, c/o The Chicago Tribune, P.O. Box 36352, Cincinnati, OH 45236-0352. Questions will be answered only in the column. For step-by-step photos of Tim hanging an interior door and other tips on trouble-free doors, please send $3 to the above address. Ask for Builder Bulletin No. 370. Want to talk to Tim? Call him from 9 to 11 a.m. Central on Saturdays toll-free at 888-737-1450. Surf with Tim at www.askthebuilder.com.