When it’s time to replace an ailing door or perhaps upgrade to something new, for most applications your best bet is going to be a prehung door unit. A prehung door simply means that the door is already mounted onto the frame, which saves you all the work of mortising the frame and the door to receive the hinges. The door and the frame are also predrilled and mortised to receive the knob and strike, and exterior prehung doors also have the weatherstripping and sill attached.
While using prehung doors will greatly simplify your installation, you need to be certain that the door is correctly ordered to fit the opening. Home centers and lumberyards often have certain common sizes and styles of doors in stock, or you can special-order doors in a huge variety of styles and sizes to fit any opening in your home.
ORDERING YOUR NEW PREHUNG DOOR
When it comes time to order your new prehung door, you need to know several things:
1. The type of door: The obvious first thing is what type of door you want. Prehung doors are available in wood, wood composites, fiberglass and metal. You can choose between paint-grade and stain-grade doors, as well as hundreds of different styles. You will also have a choice between solid-core doors, which are heavier, quieter and more secure, and hollow-core doors, which are less expensive.
2. The size of the door: Doors are available in a wide range of standard sizes, and just about any custom size. However, the most common — and therefore the most reasonably priced — are in widths between 2 and 3 feet, in 2-inch increments. The standard height of a door will be 6 feet 8 inches; 7-foot doors are also commonly available, as well as other heights by special order.
Remember that when you specify a door’s size, you are referring to the door itself, not the overall size of the prehung unit. A common example would be a 2-6 6-8 door, meaning that the door will be 2 feet, 6 inches wide and 6 feet 8 inches high. Feet and inches are the most common way of specifying a door, but you will also see them referred to in inches — in this case a 30-inch-by-80-inch door.
3. The swing of the door: To determine this, look at the door as you walk through it, with the door opening away from you. If the hinges are on the left, it’s a left-hand door. If they’re on the right, it’s a right-hand door.
4. What type of frame you want: Frames are available in paint-grade wood or wood composites, stain-grain solid or veneered wood, and also metal.
5. The width of the jambs: The jambs are the three pieces of material that make up the frame of the door, and they need to be sized to the finished depth of the door opening. Probably the most readily available jamb size is 4 9/16 inches, which is sized for installation into a wall that is framed with 2 x 4 lumber and has a 1/2 inch of drywall on each side. Another common size is 6 9/16 inches, which is intended for use in walls framed with 2 x 6 lumber and having 1/2 inch of drywall on each side.
6. The bore: Prehung doors are also prebored to receive the doorknob. Most doorknobs are a standard size, so you typically don’t really need to worry about specifying the size or location of the bore. The exception to this is if you are reusing antique knobs, or if you are using certain high-end knobs that have a different bore size or backset (the distance from the edge of the door to the center of the knob). If you have any questions about whether or not the knobs you’ll be using are standard, be sure and obtain the knobs before ordering the doors, and have the doors bored accordingly.
7. Exterior doors: For exterior prehung doors, you will typically also get the sill, door bottom and the weatherstripping pre-installed, which is another great timesaver. The sill may be aluminum in either mill finish (silver) or anodized bronze finish, or it may be wood, typically oak or other hardwood. The door bottom is usually aluminum, and the weatherstripping is most commonly a fabric-covered foam that snaps into a slot in the frame, and is very effective at stopping drafts.
8. Special sizes: If you are framing or remodeling the wall where the door will go, ask your door supplier what size the opening in the wall should be to receive the new door. This is called the rough opening, and is usually about 2 inches larger in both width and height than the size of the door, which allows room for the frame and some extra space for shimming the door plumb.
If you are replacing an existing door, your best bet is to remove the old door and frame first, then get an exact measurement of the height and width of the opening, as well as the depth of the opening between the two finished wall surfaces. If you have these measurements for the door supplier, you’ll be assured of getting a door that fits the opening without any problems.
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