What a prehung unit and a bare slab each include, when your existing jamb is sound enough for a slab, and how the installed cost really compares.
Buy a prehung door if the existing jamb is rotted, racked, or you want to change the door's size — the unit arrives already hung in a new frame with a new sill and weatherstripping. Buy a slab if the jamb is sound and square, because you keep the frame and only swap the door.
When a contractor quotes a new front door they are quoting one of two very different products. A slab is the door panel by itself — no frame, no hinges mortised, no sill. A prehung unit is the door already hanging in a brand-new frame, hinges mortised at the factory, sill and threshold attached, weatherstripping in place. Everything else about the quote — labor, warranty, how long you have no front door — follows from that one choice.
In windows, an insert replacement drops a new window into the frame already in the wall, while a full-frame replacement strips the opening back to the rough framing and rebuilds it. The tradeoffs are identical. A slab is the insert: you reuse the existing frame and jamb, so it is cheaper, faster, less disruptive, and completely dependent on the existing frame being sound. A prehung unit is the full-frame: new frame, new jamb, new sill. It resets the opening, which makes it the only version that fixes rot, water damage, or an opening that has shifted out of square.
The reason full-frame wins arguments in windows is the reason prehung wins them in doors: an insert or a slab inherits every problem the old frame already has, and hides it behind something new.
Just the panel. To install it a carpenter must make the new door match the frame already in your wall: mortise the hinge gains to line up exactly with existing hinge positions, bore lockset and deadbolt holes at existing heights, trim the edges so the reveal is even on all four sides, then bevel the latch edge so the door clears as it swings.
Slabs make sense in a specific situation: the jamb is dry and solid, the sill intact, the opening square, and you are keeping the same size and swing. That is a real and common situation, especially in newer homes or where a previous owner already replaced the frame.
An assembled system. ProVia publishes exactly what ships: the door already assembled inside the frame, a pre-finished slab and frame with matching touch-up color, pre-cut casing, aluminum cladding for the brickmold, mull covers for transoms or sidelites, a pre-installed threshold, pre-installed hinges and accessories with the lockset packed separately, and an optional installation kit with insulation, caulk, screws and shims (provia.com/doors/prehung).
The practical point: the hard alignment work — hinge placement, reveal, latch geometry, threshold seal — was done in a factory on a jig, not on your porch. The installer's job becomes setting a known-square unit plumb and level and flashing it so water leaves the building.
It also means the jamb is part of what you are buying, and jambs differ. ProVia offers four frame materials with different warranty terms: FrameSaver full wood, PermaTech composite, FusionFrame composite, and a steel L-frame. The two composite frames are warranted against rot and decay for as long as the original purchaser owns and lives in the home, while the steel L-frame and its components carry five years (ProVia entry door warranty card, 1/28/26). If your old jamb rotted once, the material of the new one matters.
A slab only works on a jamb that is sound, square and unmodified. Any one of these rules it out:
Five minutes with a tape, a level and a screwdriver:
Fail any of those and you are buying a prehung unit, whatever the sticker price says.
The slab is the cheaper object. The slab job frequently is not the cheaper job. The fitting risk sits with labor rather than materials, because every 1/8 inch the old jamb is off is absorbed by hand-planing, shimming or re-mortising. You also inherit the old weather seal — the existing weatherstripping, sill and threshold, which are the exact parts that fail first and cause the drafts most people are replacing the door to fix. Hardware rarely lines up, because older hinge spacing and lockset heights routinely differ from what a stock slab is machined for. Factory finish usually is not included either: ProVia's warranty requires primed slabs be finished with a high-quality exterior-grade paint or stain within 90 days of installation. And warranty coverage narrows, because manufacturer warranties are largely written around complete door systems — slab, frame, sill, weatherstripping and glass together — so if you buy only the slab, the parts that manage water sit outside the warranty.
Most installers quote prehung, and the reason is water rather than upselling. The parts keeping water out of the wall — sill pan, threshold, flashing behind the brickmold — are all part of the frame. An installer reusing your jamb is warranting their work on top of someone else's assembly and cannot see what is behind it. Prehung also gives a predictable factory-square unit, which makes labor estimates reliable.
That said, a contractor quoting prehung pricing over the phone has not inspected anything. Ask for the jamb, sill and squareness to be checked in person, and ask which specific answer changed after they looked. If the jamb genuinely checks out, a slab is a legitimate lower-cost path and a good installer will say so.
Replacing an entry door is also worth doing well for a reason that has nothing to do with the door itself: steel entry door replacement recoups 216.4% of its cost at resale according to the 2025 Cost vs. Value Report, the highest cost-recouped figure the report tracks. ©2025 Zonda Media, a Delaware corporation. Complete data from the 2025 Cost vs. Value Report can be downloaded free at www.costvsvalue.com.
Prehung is the doors version of a full-frame replacement; a slab is the doors version of an insert. If the jamb is dry, square and unmodified and you are keeping the same size and swing, a slab is the cheaper, faster and entirely reasonable choice. If the diagonals are off by more than a quarter inch, a screwdriver sinks into the jamb or sill, or there is water staining on interior trim, the cheaper object becomes the more expensive job — and prehung is what actually fixes the opening.
Get Door Replacement Quotes →These are the questions homeowners ask most often before starting this project - what it costs, how long it takes, what a fair quote looks like and which details change the price. Each answer below is written to stand on its own, so you can read just the one you need.
