When your DIY project calls for the installation of a new door, you’ll want a base of knowledge about the two types of door units you can use: prehung and slab.
Interior door basics
Door installation can mean inserting a door into an existing door opening or existing door frame (these two terms are not quite synonymous), or it can mean installing a door in a wall that you are building from scratch.
- Installing into an existing door opening. This method applies when you have a door opening but no door frame or door itself. You will first need to build the door frame in the opening (most do this with door frame kits from a hardware store). Then you will install a slab door onto that new frame. You can also install a prehung door into the opening. Prehung door units come with a door slab already hung on frame hinges.
- Installing slab doors onto an existing frame. In many cases, you may have an existing door frame to work with. This means you can install a slab door onto the existing frame. You would buy the door slab, create a mortise for hinges, and then hang the slab on frame hinges.
- Building a door frame from scratch. If you are embarking on new construction of a wall, you will need to build a new door frame into that wall. This means you will build a door opening and either install a prehung door unit or hang a slab door.
What is a prehung door?
Prehung doors are special types of doors that come attached to an existing door frame. Rather than have to assemble a new frame within a door opening, you can install a complete prehung unit—including door slap, hinges, and frame—in one fell swoop.
Advantages of prehung doors
Contractors and DIY home renovators choose prehung doors for a number of reasons.
- They make great exterior entry doors. Exterior prehung doors are assembled to be weathertight at the factory. This spares you the extra work of figuring out how to weatherproof your doorway and cut out drafts.
- They can save you money. Prehung doors cost more off the shelf than slab doors. However you can end up saving money when it comes to installation fees. It might take a carpenter most of the day to build a door frame, chisel mortises, drill frame hinges, and successfully hang a door. Save on fees by letting that carpenter start off with a prehung unit.
- Quality control. The majority of prehung doors sold in hardware stores come from major manufacturers, which comes with a degree of quality control and precision manufacturing.
How is a prehung door installed?
Prehung doors slot into existing door openings. If you’re ready to install your own prehung door for a DIY project, follow this step-by-step guide as you work.
- Assemble equipment. To successfully install a prehung door, you will need the prehung door itself, wood shims, nails, a hammer, a hand saw, a circular saw, a file, sanding equipment, a tape measure, and a pencil. Depending on your door model, you may also need extra hardware like a strike plate.
- Unwrap the door. Keep the prehung door in its packing restraints until you are ready to install it. This will keep it stable and prevent it from swinging. (Prehung door frames can be surprisingly flimsy until they are bolted to a wall.)
- Prepare your rough door opening for installation. Your opening should be a half-inch wider and taller than the prehung unit you’re about to install. Make sure all surfaces are completely level with no twists and no nails or screws sticking out of the rough opening.
- Trim your door jamb to fit the opening. Use one of your saws, a file, or a sanding device to trim your door jamb to the necessary size. Plan on a two-inch gap between the bottom of your door and an unfinished floor, or a half-inch gap between the bottom of your door and a floor with finish.
- Level and attach the hinge side of the doorframe. Start installing the door on its hinge side. You can temporarily hold it in place using wood shims and finishing nails.
- Move on to the latch side. Once your hinge side is set in place, move on to the latch side of the doorframe. Once again use shims and finishing nails to attach the frame to the rough door opening.
- Attach the top of the frame. Insert a shim into the very top of the prehung unit. Nail it in with finish nails.
- Continue to add shims where needed. A typical prehung door will have wood shims every foot (twelve inches) to hold it in place and maintain its rectangular shape.
- Finish with plaster and trim. With the prehung door properly nailed into the rough opening, you’re ready to add plaster and door trim to finish the project on an aesthetic level.
What is a slab door?
Slab doors are door panels that arrive detached from a door frame. They can function as both interior doors and exterior entry doors. Some come with pre-drilled mortises for hardware like door hinges, door latches, and faceplates. Others come as solid wood slabs and the installer must chisel out their own mortises.
You get a lot of options when it comes to slab doors.