When you shop for doors, you meet two different products that share a name: a pre-hung door, which arrives with its frame attached, and a slab door, which is just the door itself. The distinction matters most when you plan to do the installation yourself, because buying the wrong type means the door may not fit the opening at all. Interior and exterior doors follow the same logic, with exterior units adding weatherstripping and threshold details. If you are replacing a door in an existing wall, the frame condition often decides the purchase; a wall with a sound frame can take a slab, while a rotten or out-of-square frame calls for a complete unit such as a split-jamb pre-hung door you install as one assembly.
What Is a Pre-Hung Door?
A pre-hung door is a slab attached by hinges to a three-sided frame, sold as one ready-to-install package. The factory does the critical alignment work: hinges are mortised, the strike plate is installed, the doorknob hole is pre-cut, and the frame is sized to the opening. You lift the unit into the rough opening, shim it plumb, and fasten it through the frame. Shipping protection matters with these units; manufacturers bundle them with polyester tension straps and plastic spacers so the door does not twist in transit.
What Comes in the Box
Pre-hung units include the door slab, hinges, frame, and a strike plate pre-cut for the latch. They do not include the doorknob, the surface coating, fasteners, or shims, so budget those separately. Exterior versions add a weatherstripped threshold and often pre-drilled hardware holes.
| Included | Pre-hung | Slab |
|---|---|---|
| Door leaf | Yes | Yes |
| Frame | Yes | No |
| Hinges installed | Yes | No |
| Strike plate | Yes | No |
| Doorknob | No | No |
| Shims and fasteners | No | No |
Why ‘Slab’ Means Two Different Things
The word slab causes confusion on construction sites because it names two unrelated things. In doors, a slab is a single solid door leaf with no frame. In concrete work, a slab is a horizontal structural element, such as the floor of a house or the deck of a parking garage. A comparison of waffle slabs versus ribbed slabs discusses the concrete version, which has nothing to do with door shopping. Keep the two meanings separate when you read product listings: a slab door order will not arrive with any concrete.
Split-Jamb Variants
Split-jamb pre-hung doors are built for walls of varying thickness. The frame comes in two halves that interlock in the middle of the wall, so the unit fits 4-9/16-inch interior walls and thicker exterior assemblies without custom milling. A single package includes both halves, which is what makes the unit feel ready to go.
What Is a Slab Door?
A slab door is a bare door leaf: flat stock, hinges not attached, no frame, no hardware holes beyond what the manufacturer mills. It is cheaper to buy and cheaper to ship, but every installation task moves to your workshop. You mortise the hinges, bore the lockset, plane the edges to fit, and hang the door in an existing frame.
When a Slab Door Makes Sense
Slab doors shine in three situations.
- The existing frame is square, solid, and worth keeping, so a slab replaces the worn leaf at a fraction of the cost of a full unit.
- You are building the jambs yourself in new interior work, and a slab lets you match custom casing and trim.
- You want specialty woods that a mill shop can supply as a slab, the only way to get the grain you want without paying for a full pre-hung assembly.
The Hanging Workload
Budget real time for slab installation. Mortising three hinges, boring a lockset, fitting the door to the jamb, and adjusting the reveal typically takes an experienced DIYer a full afternoon plus a chisel set, a router, and a boring jig. Get the hinges slightly wrong and the door binds or the latch misses the strike plate. For a first-timer, the framing and hanging details shown in a split-jamb pre-hung door installation tutorial clarify how the jamb, hinges, and casing interact, and that understanding carries over when you hang a slab in an existing frame.
Installation Requirements and Rough Openings
Installation difficulty separates the two products more than purchase price does. A pre-hung unit demands careful shimming and fastening but removes the precision joinery. A slab demands joinery but simplifies lifting: a hollow-core slab weighs 20 to 40 pounds, while a pre-hung exterior unit with frame and threshold can weigh 100 pounds or more and needs two people.
Framing the Rough Opening
The rough opening must be plumb, level, and square before either product goes in. For a pre-hung unit, the frame is built to a standard size, so the opening must match within about 1/2 inch total. For a slab, you fit the leaf to whatever opening exists, which forgives framing errors but transfers all that adjustment work to the installer.
Doors and Slab-on-Grade Foundations
Exterior doors in homes built on concrete slabs sit directly on the foundation, and the slab condition affects the door’s performance. A floor slab that slopes, spalls, or wicks moisture ruins thresholds and weatherstripping within a few seasons. Understanding slab insulation fundamentals, including perimeter versus full under-slab insulation strategies, matters here because an uninsulated slab edge stays cold in winter, and that cold travels up through the door sill and into the entry.
Thresholds and Weatherstripping
Set the threshold on a solid, level bearing surface, seal the joint between threshold and slab with a flexible exterior caulk, and leave the sill pan flashing in place. A 1/8-inch gap under the door is normal; a gap at the threshold corners is not, and it will leak air and water.
Cost Comparison
Price is the reason most people first compare these products. A basic hollow-core slab door can cost $30 to $80, while the same door as a pre-hung unit runs $80 to $200. Solid-core slabs start around $100, and pre-hung solid-core or exterior units climb from $200 to $600 or more. The installed cost narrows the gap: paying a carpenter to hang and fit a slab can equal the difference in purchase price.
| Item | Slab door | Pre-hung door |
|---|---|---|
| Typical purchase price | $30-$100 | $80-$600+ |
| Hardware | Knob, hinges, and tools extra | Knob only |
| DIY installation time | Half to full day | 2-4 hours per door |
| Pro installation cost | Higher per door | Lower per door |
The Hidden Costs
Slab buyers pay for tools and mistakes. Hinge mortising jigs, lockset boring kits, and router bits add $100 or more if you do not already own them. A mis-hung door that binds or leaks costs time to correct, and a damaged slab is rarely returnable. Pre-hung buyers pay a higher purchase price but face fewer tool costs, since the precision work is already done.
Foundations and Door Budgets
On a house with a concrete slab, door replacement sometimes exposes foundation issues that belong in the budget. Cracks at the threshold, uneven bearing, and settlement all trace back to how the slab was built. Reviewing slab foundation design, construction, and best practices for concrete slab-on-grade systems helps you tell a cosmetic crack from a structural one before you spend money on the door.
Energy Performance and Comfort
Door performance is a big part of a home’s air-sealing story. A pre-hung exterior unit ships with factory weatherstripping, a bottom sweep, and a threshold designed to close the gap; a slab retrofit depends on whatever weatherstripping you add afterward. In energy terms, the frame and sill matter as much as the leaf.
Air Sealing at the Entry
Check four points on every exterior door:
- The gap under the leaf, where a sweep or threshold seal closes the draft.
- The hinge-side jamb, where warped casing opens a visible crack.
- The latch-side stop, where the door meets the frame.
- The threshold, where cold air rides in over the sill.
A dollar’s worth of foam tape or a new door sweep fixes most drafts. On cold-climate homes, the entry floor is a thermal weak point even with a good door.
Radiant Slab Homes
In houses with in-floor radiant heat, the entry door interacts with a heated slab. The threshold must tolerate the slab’s movement and temperature, and the slab itself needs correct insulation placement to keep heat in the floor rather than leaking out the edge. Choosing the right foam board when insulating under a radiant slab keeps the entry comfortable and stops the door sill from becoming a cold bridge.
Choose the product that matches your skill level, your frame’s condition, and your budget. A slab door rewards a careful woodworker with the lowest material cost; a pre-hung unit rewards almost anyone with a faster, more predictable installation. On slab-built houses, pair the door decision with a look at the foundation underneath, because the two work together. The same concrete slab foundation design and construction best practices that keep a floor level also keep its doors closing straight for decades.