Fit a Slab Door Into an Existing Jamb
The jamb and casing are fine, the door is not. A bare slab from the store fitted to the frame you have — hinge mortises cut to match, lock bored, edges planed until it swings clean.
JMB Builders will fit a slab door to an existing frame anywhere in the Twin Cities metro. We transfer the hinge locations from the old door, mortise the new slab to match, bore for the knob and latch, bevel the strike edge and plane it to an even gap all the way around, then hang it and set the strike. Priced per door, quoted from photos within one business day.
- Priced per door, slab fitted to your jamb
- Hinges mortised, lock bored, edges planed
- Quote from photos in 1 business day
- Licensed MN contractor BC809005
A slab is a door with nothing on it: no jamb, no hinges, no holes. It is the cheapest way to replace a door, and the hardest way to hang one, because every cut has to line up with a jamb that somebody else built years ago. The hinge mortises on the jamb are wherever they are. The strike is where it is. The head of the jamb might be an eighth out of level. Fitting the slab means making the new door agree with all of that.
We do it the old way. The old door comes off and goes on the bench next to the new slab. Hinge locations are transferred, mortises cut with a router or a chisel to the exact hinge size, the lock bore drilled at the same height and backset so the existing strike still works, the strike edge beveled about three degrees so it clears the stop, and the edges planed until there is an even gap at the top and both sides. Then it goes on the hinges and gets adjusted until it latches with a light push.
What you supply
- The slab: same width and height as the old door (or larger, we can trim), same thickness (1-3/8 interior, 1-3/4 exterior)
- Hinges if the old ones are worn or a different finish; same size as the jamb mortises, usually 3-1/2 or 4 inch
- Knob or lever set, and deadbolt if it is an exterior door
- Your paint or stain color if the slab comes primed and we are finishing it; painting is quoted as a separate line
What JMB supplies
- Removal of the old slab and its hardware
- Hinge mortises cut to match your jamb, lock and latch bores at the right height and backset
- Edges planed and beveled, bottom cut for clearance over the finished floor
- Reuse or replacement of the strike plate and adjustment so the latch catches
- Jamb repair when a hinge mortise is chewed out or the screw holes are stripped
- Photos of the finished door in your job folder
- Painting or staining the new slab when you want it done, quoted as its own line
How it is priced: per door
Quoted in writing from your photos within one business day. What moves the number:
- Hollow-core vs. solid-core or solid wood slab; solid doors take longer to plane and hang
- Whether the slab has to be cut down in width or height to fit the opening
- Number of hinges (two on older interior doors, three on most, four on tall or heavy doors)
- Condition of the jamb: stripped hinge screws, split mortises or a racked frame add time
- Exterior slab with a deadbolt bore, weatherstrip and sweep vs. an interior door
- Number of slabs in the same visit; a whole-house slab swap is cheapest per door
Send a photo of the old door open, showing the hinges and the edge with the latch, plus the width, height and thickness on a tape.
How long it takes
One interior slab: two to three hours. A whole-house slab swap: four to six doors a day. Exterior slabs with a deadbolt and weatherstrip take longer.
How your project works
- 1
Send photos, get a written quote
Send three photos of the space and a sentence about what you want. You get a clear, itemized quote within one business day. We only come out to measure first when the job needs a tape measure — no pressure, no games.
- 2
Pick materials, or bring your own
We help you choose profiles and materials that fit the house and the budget, or match your existing millwork exactly — or you buy the door or trim yourself and we install it. Everything is confirmed before the crew is scheduled.
- 3
Clean, precise installation
The crew shows up on time, protects floors and furniture, and installs with tight joints and consistent reveals. Photos of the finished work go in your job folder.
- 4
Walkthrough and invoice
We walk the finished work with you. If anything is not right, we fix it before we call the job done. Then one invoice, paid by check or direct deposit — no card fees, no payment links.
Situations and options
Match the old door exactly
The most common case: a damaged or dated slab in a jamb that is fine. We copy the hinge and lock layout from the old door onto the new slab so the existing jamb, strike and stop are untouched.
Hollow-core to solid-core swap
Same jamb, quieter room. A solid-core slab is heavier, so we check the hinge screws are biting solid wood, sometimes swap to three hinges, and plane the edges carefully because a solid door does not forgive a tight margin.
Non-standard old doors
Older Twin Cities homes have 78-inch doors, 1-3/8 exterior doors and odd widths. We cut a standard slab down to size, keeping the panel layout centered, and re-cap a hollow-core slab if the cut removes the bottom rail.
When the jamb is too far gone
A jamb that is split at the hinges, kicked out at the strike or racked more than we can plane around is not worth fitting a slab to. We tell you, and quote a prehung unit instead so the new door has a square frame to live in.
Fit a Slab Door Into an Existing Jamb: questions, answered
Can you install a slab door in my existing jamb?
Yes. That is what a slab install is: your jamb, casing and strike stay, and the new door is fitted to them. We mortise the hinges to match the jamb, bore for the knob and latch at the same height and backset as the old door, plane the edges for an even gap and hang it. Priced per door across the Twin Cities metro, quoted from photos within one business day.
How do I know what size slab door to buy?
Measure the old door itself, not the opening: width, height and thickness. Interior doors are usually 1-3/8 inch thick and 80 inches tall; widths run 24, 28, 30, 32 and 36 inches. Buy the same size, or the next size up if the old door has been trimmed a lot, and we cut it to fit. Check the hinge size too; a 4-inch hinge will not sit in a 3-1/2 inch mortise without cutting.
Do you have to cut new hinge mortises on a slab door?
Yes, on a true slab. Some stores sell slabs that are pre-mortised and pre-bored to a standard layout; those only work if your jamb matches that layout, which is rare on an older house. We lay out the mortises from your jamb, cut them to the hinge's depth and radius, and the door sits flush without binding.
What if the existing jamb is out of square?
Most are, a little. We plane the slab to follow the jamb so the gap looks even even if the frame is not perfect, and we can shim behind a hinge to pull the door into line. If the jamb is racked enough that the door would need a wedge-shaped cut, or the hinge side is split and the screws will not hold, we tell you and price a prehung unit instead.
Can you hang a slab door and reuse my old hinges and knob?
Usually. Old hinges that are not bent or worn go right back on, which keeps the mortise layout simple. Knobs come off and go on the new slab as long as the bore size and backset match what we drill, which they do on standard hardware. If the finish is worn or you want levers, buy new hardware before install day and we put it on.
Can a hollow-core slab be trimmed to fit a shorter opening?
Up to a point. The bottom of a hollow-core door has a solid rail that is only an inch or so tall. Cutting less than that is fine. Cutting more removes the rail, so we cut the rail free of the skins, glue it back into the door and clamp it. It is a normal part of fitting slabs in older homes with 78-inch openings.
Get a written quote for this job
Three photos and a sentence is enough. You hear back within one business day. Or text the photos to 763-204-2099.
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Read morePage reviewed September 24, 2026 · JMB Builders LLC, MN license BC809005 · All doors pages
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