Replacing an interior door is one of the projects that intimidates DIYers more than it should — until they pick the wrong style of door for the situation and end up with a multi-day frustration project. What is a prehung interior door matters because it’s the difference between a 90-minute install and a full-day project that requires a router, chisel set, and a finish carpenter’s eye. A prehung door is a complete door assembly — door slab, frame, jamb, and hinges — already assembled at the factory. You install it as one unit, plumb and shim the frame, nail it in, and trim it out.
Prehung vs. Slab: The Core Difference
A slab door is just the door panel — no jamb, no hinges installed, no doorknob holes drilled. A prehung door arrives with everything pre-assembled. Choose based on your situation:
- Prehung: Use when the existing frame is damaged, the rough opening is to-spec for a new install, or you’re framing new openings
- Slab: Use when the existing jamb is straight, square, and in good condition and you just want a new door
Prehung doors run $100 to $400 for hollow-core interior, $200 to $700 for solid-core, plus delivery if too big to fit in a car (most are). Slab doors run $40 to $250 for hollow-core, $100 to $400 for solid-core.
Anatomy of a Prehung Door
A prehung door includes:
- The door slab itself (hollow core, solid core, or solid wood)
- A three-piece jamb: two side jambs and one head jamb, joined at the corners
- Three hinges (or two on shorter doors) attached to both the door and the jamb
- A pre-bored 2-1/8 inch hole for the doorknob and a 1-inch latch hole edge-bored
- A strike plate mortise cut into the latch-side jamb
Most prehung doors do NOT include casing (the decorative trim), the doorknob, or the strike plate hardware itself. Add those to your shopping list separately.
Sizing a Prehung Door
Standard interior prehung doors come in widths of 24, 28, 30, 32, and 36 inches, with 80 inches the standard height. The “32-inch door” refers to the door slab width — the rough opening (the framed hole in the wall before the door goes in) needs to be 34 inches wide and 82.5 inches tall to accommodate the jamb and shims.
Standard rough opening formula: door width + 2 inches, door height + 2.5 inches. Measure your existing rough opening before buying — closing in 1 inch on a too-wide opening is easy, but a too-small opening means cutting studs.
Door Swing: Left-Hand vs. Right-Hand
Order the wrong swing and you’ll be returning the door to the lumber yard. To determine swing:
- Stand on the side of the door that allows it to swing TOWARD you
- If the hinges are on the left, it’s a left-hand door
- If the hinges are on the right, it’s a right-hand door
Some manufacturers further distinguish “inswing” vs. “outswing,” but for interior doors this matters less than for exterior. Sketch your floor plan, mark the wall, and indicate which way the door should open before going to the store.
Core Type Matters More Than Style
The single most important spec to upgrade is the door core. Three options:
- Hollow-core ($75 to $150): Honeycomb cardboard interior; light, cheap, sounds hollow when tapped
- Solid-core ($150 to $300): Particleboard or MDF interior; heavier, blocks sound much better, feels substantial
- Solid wood ($250 to $700): Real wood stiles and rails; best sound blocking and visual quality, expensive
Solid-core is the sweet spot for bedrooms, bathrooms, and offices where sound privacy matters. The STC (sound transmission class) jump from hollow-core (about 17) to solid-core (about 28) is dramatic.
Top Prehung Door Brands
- JELD-WEN: The Home Depot mainstay; consistent quality across price points, available in most styles
- Masonite: Lowe’s primary supplier; molded panel doors with consistent factory primer
- Bayer Built: Higher-end primed and pre-finished options; popular with custom builders
- TruStile: Custom solid-wood doors; lead time 4 to 8 weeks, premium pricing
For most renovations, JELD-WEN or Masonite covers the range from budget builder-grade to mid-tier solid-core at competitive prices.
How to Install: The 90-Minute Version
Tools you’ll need: 4-foot level, hammer, finish nail gun or 8d finish nails, shims (cedar wedge shims, $4 per bundle), and a utility knife.
- Remove the existing door, jamb, and trim from the opening
- Check the rough opening for square (diagonal measurements should match within 1/4 inch) and plumb
- Slide the prehung door assembly into the opening from the hinge side first
- Place shims behind each hinge location on the hinge-side jamb; check plumb with the level
- Nail through the jamb and shims into the framing with 8d finish nails
- Shim the latch-side jamb at the top, middle, and strike plate — aim for an even 1/8 inch gap between door and jamb (a quarter coin works as a feeler gauge)
- Nail through the latch-side jamb at each shim location
- Trim shims flush with the wall using a utility knife
- Install casing trim on both sides of the door
Common Installation Mistakes
- Not checking plumb in two planes: The jamb needs to be plumb both vertically and perpendicular to the wall surface
- Skipping shims at the strike plate: The door will sag and stop latching properly
- Nailing too tight before checking: Test the door swing before driving final nails
- Using construction adhesive on the jamb: Makes future repairs impossible
If the door binds when closing, the jamb isn’t plumb. Loosen the offending nail, re-shim, and check again. A correctly hung door swings smoothly with no tendency to drift open or closed when released halfway.
Casing and Finishing
Casing comes in two forms: pre-mitered casing kits (about $35 to $80 per door) that include the corners precut at 45 degrees, or by-the-foot trim that you cut yourself. The kits are fool-proof but limit your trim choice. By-the-foot 3-1/4 inch colonial casing runs $1.20 to $2.50 per linear foot.
For paint-grade doors, use Sherwin Williams Emerald Urethane Trim Enamel ($85 per gallon) — it self-levels for a brush-stroke-free finish and resists yellowing on white doors. Apply two coats over the factory primer.
Hardware Selection
Standard 2-3/8 inch backset doorknobs fit most prehung doors. The Schlage F-Series ($35 to $80) and Kwikset SmartCode ($45 to $130 for keyless) cover the mainstream. Match finishes across the home for visual cohesion — switching between satin nickel and matte black on the same floor looks jarring.
Understanding what a prehung interior door is — and when to choose one over a slab — saves time, money, and the frustration of a project that goes sideways. For most homeowners replacing existing damaged frames or adding new openings, prehung is the right call. Choose solid-core for any room where privacy matters, measure the rough opening before buying, and invest in proper shims and a long level. Done right, a prehung door installs in under two hours and looks like a professional’s work.
