Updated September 29, 2026 by Chris Horton. Decision help, not an installation method verdict. How we estimate costs
For homeowners deciding between a slab-only swap, a prehung unit and a full-frame replacement on an exterior door. Five steps. At the end you get the paths that fit what you described, the measurements still needed to lock the decision, the scope you should expect in each quote, and the questions to send installers. There is no universal winner. The right one depends on the jamb, the sill and the opening, not on which is cheapest on paper.
A slab is the door panel alone. A prehung unit is the door already mounted in a new jamb, delivered as one piece. A full-frame replacement removes the jamb and sill back to the rough opening and starts over with new flashing. In rising order of scope, cost and disruption.
Answer from what you can see and touch on the current door. Where you are not sure, choose Not sure: that becomes a measurement or an installer question, not a guess.
Step 1 of 5 · The door and the opening
The door and the opening
Start with what you have, not what you want.
Jamb and threshold condition
This is where slab, prehung and full-frame diverge. Look and touch, do not assume.
Hardware, hinges and lock
Slab-only feasibility depends on these matching between old and new.
What you want to change
Some upgrades force full-frame regardless of everything above.
Where you are, based on what you described
Installation paths
Fits your case means what you described points to this method. Worth investigating means it could fit but needs more information. Unlikely to help means what you described points away. Needs a professional means the choice depends on measurements a homeowner cannot reasonably take.
Scope differences to expect in the quotes
Measurements still required
Questions to send every installer
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This tool needs JavaScript. The framework is explained in our door replacement quote audit.
What this tool does, and what it does not
It can help you
- Name which installation paths fit what you described.
- Surface the measurements a slab-only decision depends on.
- Explain the scope differences between slab, prehung and full-frame quotes.
- Prepare the questions to send every installer.
- Recognise when the honest answer is that only an on-site pro can decide.
It cannot tell you
- Which method is right for your door. Only an on-site installer can decide with measurements.
- Whether the flashing behind the trim is sound.
- The cost of any method in your local market.
- Which installer to hire.
- Whether a specific slab door will fit your existing jamb without on-site measurements.
Where to go next
- Door Quote Analyzer — break down a written quote.
- Door Replacement Cost Calculator — published planning ranges.
- Front door replacement cost — the drivers.
- Patio door replacement cost.
- Door warranties explained.
- All doors guides and how we estimate costs.
About the author
Chris Horton writes UpgradeWorth’s homeowner decision guides. He covers how replacement projects are scoped, quoted and warrantied, with a bias toward what a homeowner can verify in writing rather than what a salesperson says at the kitchen table. UpgradeWorth does not sell leads, rank contractors or accept placement fees.