A prehung door comes already hung on hinges in its own three-sided frame, usually with the knob hole drilled, so you install the whole unit in the wall opening. A slab door is just the door panel, with no frame or hinges, so it has to be fitted to a frame you already have. Slabs cost less and suit a same-size swap into a good, square frame. Prehung doors are easier to get right and are usually the better pick for exterior doors, new openings or a damaged frame.
- Prehung: door + frame + hinges, with hinge and lock prep already done. You replace the whole frame.
- Slab: the door panel only. You fit it to your existing frame, cutting hinge recesses and drilling for the lock if needed.
- Skill: slabs take careful carpentry to swing and close well; prehung units still need shimming, leveling and squaring, but the door-to-frame fit is done.
- Cost: slabs usually cost less to buy; prehung units cost more but save fitting work.
- Exterior doors: prehung is usually better, because the frame, seal and threshold come as one weather-tight unit (DOE says new prehung exterior doors should have weatherstripping installed).
- Interior doors: a slab works well for a same-size swap into a sound, square frame.
- Lily Ann Cabinets sells prehung 36" x 80" fiberglass entry doors, such as the Mahogany Castleview (in stock September 28, 2026; local pickup or delivery). We don't sell slab doors.
When you shop for a new door, you'll quickly run into two ways it can be sold: prehung or slab. They can be the same door, but they're very different to buy and install. Pick the wrong one and the door may not fit, or you may end up doing a lot more carpentry than you planned.
This guide compares the two fairly: what each includes, how hard each is to install, how the cost compares, and when to choose which. One thing up front: Lily Ann Cabinets sells prehung fiberglass entry doors, and no slab doors. We've still tried to give slabs a fair write-up, because for many interior doors a slab is the better choice. Lily Ann specs and stock below were checked on the live site on September 28, 2026.
Prehung vs. Slab Door: The Short Answer
A prehung door is a complete unit: the door is already hung on hinges in its own frame, ready to set into the wall opening. A slab door is only the door, with no frame and usually no hinges, and it has to be fitted to an existing frame. Choose prehung for exterior doors, new openings or a damaged frame. Choose a slab for a same-size swap into a good, square frame, especially indoors.
| Prehung door | Slab door | |
|---|---|---|
| What you get | Door, three-sided frame, hinges | Door panel only |
| Hinge recesses (mortises) | Cut in the door and frame | Usually you cut them |
| Knob/lock hole | Usually pre-drilled | Sometimes; sold with or without |
| Old frame | Removed down to the rough opening | Kept; the slab hangs in it |
| Weather seal (exterior) | Frame, weatherstripping and threshold come together | Relies on the old frame's seal |
| Handling | Heavy and bulky; two people | Lighter and easier to carry |
| Install skill | Shimming, leveling, squaring, trim | Precise carpentry to fit and hang |
| Price to buy | Usually more | Usually less |
| Best for | Exterior doors, new openings, damaged frames | Same-size interior swaps, custom or salvaged doors |
Sources: The Spruce's prehung vs. slab door guide and the U.S. Department of Energy's guidance on doors. Every product is different, so check the listing to see exactly what's included.
What Is a Prehung Door?
A prehung door is a door that's already hung by its hinges in a three-sided frame (two side jambs and a head jamb). It's sold as a complete unit. The Spruce describes it as a slab door that's already attached by hinges to its frame, sold "ready to go." Prehung doors are shipped strapped into their frames with spacers so the door can't shift or twist on the way.
According to The Spruce, a typical prehung door includes the door, the hinges, the frame, the frame pre-cut for the strike plate, the hinge recesses cut in the door, and a pre-drilled hole for the doorknob. It usually doesn't include the doorknob, the metal strike plate, paint or stain, fasteners or shims.
An exterior prehung door also has to seal out weather. The DOE says new prehung exterior doors should have weatherstripping already installed. Check the listing for the threshold and weatherstripping too.
As a real example, here's what comes with Lily Ann's prehung fiberglass entry doors, from the listings:
- Door: 36" x 80" fiberglass, already stained Tan Brown or Dark Brown
- Frame: 4-9/16" composite frame; the unit is 37-1/2" x 81-1/2"
- Rough opening: 38" x 82"
- Hinges: 3 oil-rubbed bronze hinges, already mounted
- Lock prep: 2-3/4" bore for an entry lock and deadbolt (locks sold separately)
- Swing: inswing, left or right hand
What Is a Slab Door?
A slab door is the door panel by itself, with no frame, no hinges and no hardware. It's meant to hang in a frame you already have, or one you build. Some slabs come with the knob hole already drilled and some don't. On a typical slab, you cut the hinge recesses yourself to match your frame.
The Spruce lists a typical slab as including only the door and, if you choose it, a pre-cut knob hole. It doesn't include the doorknob, strike plate, finish, hinge recesses, hinges or shims. Some sellers will machine a slab for hinges and a lock for an extra charge, so read the listing closely before you order.
A door that isn't prehung is simply called a slab, or a slab-only door.
Not to be confused with: in kitchens, a "slab door" means a flat cabinet door with no raised or recessed panel. That's a door style, not a way of selling a door. If that's what you're after, see shaker vs. slab cabinets.
Installation: Which Is Easier?
A prehung door is usually easier to get right, because the hardest part, fitting the door to its frame so it swings and closes well, is already done. It's still real work:
- Remove the old door, trim and frame down to the rough opening. The DOE notes you'll need to take out the existing frame before installing a prehung door.
- Set the new unit in the opening, then shim it so it's plumb, level and square. The frame has to be as square as possible so the door seals tightly and swings properly.
- Fasten the frame through the shims into the wall framing.
- For an exterior door, seal the gap between the frame and the rough opening and threshold with expanding foam before the inside trim goes on. Go easy, especially on a wood frame, so the foam doesn't push it out of square.
- Put the trim (casing) back on and install the lockset.
The Spruce's tips: keep the shipping straps and clips on until the unit is in the opening, so the door can't swing open on you. And plan on two people: prehung units are heavy and awkward, and exterior ones especially so.
A slab door takes more skill. You have to trim it to fit the old frame, cut hinge recesses that line up with the frame's hinges, and drill for the knob and latch if they aren't pre-drilled. The Spruce says it takes "a steady hand, a good eye, and plenty of practice," and that it's easiest when the new slab is exactly the same size and layout as the old door. A new slab is flatter and truer than a salvaged one, which makes it easier to hang.
Cost: Which Is Cheaper?
A slab door usually costs less to buy than the same door prehung, because you aren't paying for the frame, hinges and factory fitting. The Spruce says slabs "often cost much less" than prehung units.
The total cost can flip, though. With a slab, you may pay for hinges, a lockset and a lot more fitting time, or a carpenter's time. With a prehung door, you pay more up front but skip most of the fitting, and on an exterior door you get a new frame, seal and threshold at the same time. Prices vary widely by size, material and glass, so compare real quotes for the doors you're considering.
Common Problems with Prehung Doors
Prehung doors aren't foolproof. The most common problems:
- Weight and bulk. They're hard to move, may not fit in a small car, and need two people to set in place.
- A flimsy frame before it's installed. The frame only gets rigid once it's shimmed and fastened in the wall.
- No guaranteed swing. A prehung unit installed out of plumb or square can still bind, rub or not latch. Careful shimming fixes most of this.
- Foam pushing the frame. Too much expanding foam can bow a wood frame out of square, which is why DOE says to apply it carefully.
- More demolition. You have to remove the old frame and trim, so it's more work if your existing frame and casing are in good shape. The Spruce's rule of thumb is not to buy prehung if you already have a good frame with casing and trim, unless you plan to strip it to the studs anyway.
Exterior vs. Interior Doors
Exterior doors: prehung is usually the better choice. The Spruce says most retrofit exterior doors come prehung, and that prehung exterior doors come weather-tight off the shelf, while a weatherproof exterior slab is hard to install unless you're very experienced. The DOE puts it simply: when you buy a door, it will probably be prehung.
Interior doors: slabs make more sense. Interiors are more forgiving because there's no weather to seal out, and a slab is a good fit when you're swapping a door into a frame that's still sound. The Spruce also points out that slabs give you more design freedom, since antique and salvaged doors almost always come as slabs.
Prehung or Slab: Which Should You Choose?
- Choose prehung for an exterior door, a new opening, an old frame that's damaged, warped or out of square, or if you'd rather not cut hinge recesses and drill lock holes.
- Choose a slab if the existing frame is in good shape and square, the new door is the same size as the old one, you're comfortable with careful carpentry, or you want to reuse a salvaged or custom door.
- Replacing several interior doors? Many people use slabs where frames are good and prehung units where frames are damaged. There's no rule that every door in the house must be the same type.
What to Measure Before You Buy
What you measure depends on which type you're buying.
- For a slab: measure the old door's width, height and thickness, and where the hinges sit from the top and bottom. Also note the backset (how far the knob hole sits from the door's edge). Our passage door lever, for example, fits a 2-3/8" or 2-3/4" backset on doors 1-3/8" to 1-3/4" thick.
- For a prehung unit: measure the rough opening with the old frame removed, the thickness of the wall, and which way the door swings. Then match the rough opening on the spec sheet. For a 36" x 80" Lily Ann door, that's 38" x 82".
Lily Ann's Prehung Entry Doors
All of Lily Ann's entry doors are prehung fiberglass units. These 36" x 80" doors showed In Stock on September 28, 2026:
Entry doors are local orders only: pick up at a Lily Ann showroom (Adrian, MI or Clearwater, FL), or we deliver within 200 miles of one. Locks are sold separately; we carry an entry door lockset in left- and right-hand versions. To finish the inside once the frame is in, we also carry primed MDF door casing (local orders only). See the full range on our entry doors page.
A Third Option for Interior Openings: A Barn Door
If you're replacing an interior door and don't want to deal with hinges at all, a sliding barn door skips the hinged-door question. It hangs from a track on the wall above the opening. Lily Ann's knotty pine barn door is 37" wide, 84" tall and 1-3/8" thick, unfinished and ready to paint or stain, with hardware sold separately (local orders only). Barn doors trade some privacy and sound control for saved floor space; see sliding barn doors vs. traditional doors for the pros and cons, and how to install a barn door for the steps.
The Takeaway
A prehung door is the whole package, door and frame together. A slab is just the door. Slabs cost less and work well for same-size interior swaps into good frames, but they take careful carpentry. Prehung doors cost more but are easier to get right, and for an exterior door they're usually the better choice because the frame, seal and threshold come as one unit. Whichever you choose, measure first, and match the numbers to the listing.
Replacing a front door? Shop Lily Ann's prehung fiberglass entry doors.
Frequently Asked Questions
Prehung doors cost more than slabs, and they're heavy and bulky, so moving and setting one usually takes two people. You also have to remove the old frame and trim, which is extra work if your existing frame is in good shape. And a prehung door can still bind or fail to latch if it isn't shimmed plumb, level and square.
Sometimes. Slab doors are sold both with and without a pre-drilled hole for the doorknob, so check the listing before you order. Even when the knob hole is drilled, a typical slab doesn't come with hinge recesses cut, a strike plate or a knob.
Slab doors are usually cheaper to buy, because you aren't paying for a frame, hinges and factory fitting. The Spruce says slabs often cost much less than prehung units. But a slab can take more labor, hinges and hardware to hang, so compare the total cost of the finished job, not just the door.
The most common problems come from installation. A frame that isn't shimmed plumb, level and square can make the door bind, rub or not latch. Too much expanding foam can push a wood frame out of square. The frame is flimsy until it's fastened in the wall, and the unit is heavy and awkward to handle.
A prehung door is usually easier, because the door is already fitted and hinged to its frame. You still need to set, shim and fasten the unit. Hanging a slab means cutting hinge recesses, drilling for the lock and fitting the door to an existing frame, which takes careful carpentry. A slab is easiest when it's the exact same size and layout as the old door.
It's called a slab door, or just a slab. It's the door panel by itself, with no frame or hinges. In kitchen design, "slab door" also means a flat cabinet door style, which is a different thing.
Usually not. The Spruce lists hinge recesses (mortises) and hinges as things a typical slab door doesn't include, because they have to line up with the hinges on your existing frame. Some sellers offer slabs machined for hinges, so check the listing. Prehung doors come with the hinge recesses cut and the hinges mounted.
A pre-hung door is a door that's already hung on hinges in its own three-sided frame. It's sold as one unit, usually with the knob hole drilled, and it's installed by setting the whole frame into the rough opening. Lily Ann's entry doors, for example, come hung on a 4-9/16" composite frame with three hinges and a bore for an entry lock and deadbolt.
If the old frames are sound and square and the new doors are the same size, slabs are usually the cheaper choice, as long as you're comfortable cutting hinge recesses and drilling for the latch. If a frame is damaged or out of square, or you want to skip the fitting work, use a prehung door there. Mixing both in one house is fine.
Comments