Walk into any Home Depot or Lowe’s millwork aisle and you’ll see two flavors of interior doors stacked side by side: prehung units with frames and hinges, and bare panels leaning against the wall. Those bare panels answer the question of what are slab doors. A slab door is simply the door panel itself, sold without a frame, hinges, or hardware. You buy slabs when you’re keeping the existing jamb and just want to swap out the door face, and that decision can save you $80 to $250 per opening over a prehung replacement.
The Anatomy of a Slab Door
A slab is the rectangular panel between the jambs. It has no jamb assembly, no hinges, no strike plate, and no hardware bore unless you order a pre-bored option. You’ll receive a flat panel measuring something like 30×80, 32×80, or 36×80 inches, with thickness of either 1-3/8 inch for interior or 1-3/4 inch for exterior applications.
Slabs come in three construction grades. Hollow-core slabs from brands like Masonite or JELD-WEN run $35 to $90 and weigh 18 to 22 pounds. Solid-core slabs filled with composite particleboard cost $80 to $250 and weigh 45 to 70 pounds. Solid wood slabs from Sun Mountain or Trustile push $300 to $1,500 and need two people to hang.
Slab Door vs Prehung Door: Which Saves You More
The financial calculation is straightforward once you know the existing condition of your jambs. A prehung door from Masonite at Home Depot runs $140 to $400 with primed jambs, hinges, and a bore for the lockset. A comparable slab runs $65 to $200. The difference covers the jamb assembly plus factory hanging labor.
Prehung wins when you’re replacing rotted, cracked, or out-of-square jambs, or doing new construction. Slab doors win when the existing jambs are plumb, square, and structurally sound. Realistically, in a house under 30 years old with no settling issues, slabs work for at least 80 percent of door swaps.
Sizing and Pre-Bore Decisions Before You Buy
Measure the existing door, not the opening. Standard interior sizes run 24, 28, 30, 32, and 36 inches wide by 80 inches tall. Closet doors often come in 24 or 28 inches. Bedrooms and bathrooms usually hit 28 or 30, and main passage doors typically run 32 to 36.
Decide whether you want the slab pre-bored for hardware. A 2-1/8 inch bore at 36 inches from the bottom with a 1 inch edge bore fits standard Schlage, Kwikset, and Baldwin levers. Pre-bored slabs save you 20 minutes per door and the cost of a $30 boring jig. If you’re matching an existing privacy lock or installing a Emtek mortise set, order the slab blank.
Hinge Mortising and the Tools You Actually Need
The trickiest part of hanging a slab is matching the hinge positions to the existing jamb. Lay the new slab flat against the old door, align bottoms and latch edges, and trace each hinge location with a sharp pencil. Confirm a 3/16 inch gap at top and bottom for swing clearance.
Cut the hinge mortises with a sharp 1-inch chisel and a mallet or use a Porter-Cable 59370 hinge butt template kit ($85) with a router. The mortise depth must match the hinge leaf thickness, usually 1/8 inch. A loose-fitting mortise lets the door sag within a few weeks. Stanley 3-1/2 inch residential hinges run $4 to $8 each.
Step-by-Step Slab Installation
Here’s the workflow that takes a confident DIYer about 45 minutes per door once you’ve done one or two:
- Remove the old door by tapping hinge pins up and out.
- Set the new slab on shims so it sits in the rough opening with the right reveal.
- Mark hinge positions from the existing jamb, not the old door, since old doors sag.
- Cut hinge mortises with a chisel or router template.
- Install the hinge leaves on the slab edge with #9 x 1-1/4 inch screws.
- Lift the slab onto the jamb hinges and drop in the pins.
- Check the reveal at top, latch, and bottom. Adjust with one long screw per hinge if needed.
- Mark and bore the latch strike if not pre-bored.
- Install the lockset and test the strike alignment.
Common Slab Door Materials and Their Best Uses
Different rooms call for different slab constructions. A hollow-core flush slab works fine for a closet or a guest bedroom but transmits sound badly. A solid-core slab from Masonite’s Heritage line ($120 to $180) blocks 28 to 32 STC, suitable for bedrooms and home offices. MDF panel slabs from JELD-WEN’s Conmore or Cambridge lines run $90 to $160 and paint beautifully.
For pantries and laundry rooms, a glass-insert slab brings in light without sacrificing privacy. Frosted or reeded glass options from Krosswood Doors start at $220. Exterior slabs use fiberglass from Therma-Tru ($350 to $900) or steel from Pella ($250 to $600) and require weather-stripped jambs already in place.
Common Mistakes That Ruin a Slab Install
The biggest error is buying a slab that’s slightly smaller than the opening and trying to shim the hinges to compensate. The door will look acceptable but the latch will refuse to align after a few seasons. Always buy a slab equal to or up to 1/4 inch larger than the existing door, then plane the edges to fit.
The second classic mistake is forgetting to bevel the latch edge by 3 degrees toward the strike side. Without that bevel, the door binds against the jamb stop as it closes. A sharp block plane removes the material in three or four passes. Finally, prime all six edges of any wood or MDF slab before hanging. Untreated edges absorb humidity, swell within months, and cause the door to stick every summer.
