Smart lock installation runs smoothly on a door that already has a standard deadbolt prep, and turns into a carpentry job on a door that doesn't. Four measurements decide which one you're facing: door thickness, backset, crossbore diameter, and the room around that bore. Take them before you buy, because the lock has to match the holes already in your door, not the other way around.
Call a licensed local locksmith now for a fast quote on smart lock installation, or to confirm compatibility on a door you're unsure about.
What Smart Lock Installation Actually Involves
A smart deadbolt is a deadbolt first and a connected device second. The mechanical half is identical to deadbolt lock installation and repair on any bored door. The bolt assembly slides into the 1 in. hole through the door edge, faceplate set flush into a shallow mortise. The exterior keypad or cylinder plate covers the 2-1/8 in. crossbore. The interior housing, holding the motor and batteries, mounts over that same bore inside, joined through the door by a ribbon cable or a pair of posts. Two long screws clamp the halves together, a tailpiece engages the bolt, and the strike plate goes into the jamb so the bolt throws fully without dragging.
On a door already prepped for a deadbolt, that runs 20 to 40 minutes. On a door with no deadbolt hole, add boring with a hole saw and a door jig plus chiseling the jamb for the strike. Any flat "30-minute install" figure describes the first case and leaves out the second.
The electronic half, and what your house has to supply
Only after the hardware is mounted does setup begin: batteries, a keypad code or app pairing, then the radio. Settle the radio question before you order, not after.
- Bluetooth-only locks work from your phone at the door and nothing else. No opening it remotely, no guest codes issued from work.
- Wi-Fi models join 2.4 GHz networks, not 5 GHz. If your router hides both bands behind one name, you may have to split them temporarily to get the lock connected.
- Z-Wave and Zigbee locks need a hub. Budget for one if you don't already run a home automation system.
- Thread and Matter locks need a border router in the house, usually a recent smart speaker or hub rather than anything in the lock's box.
- Batteries sit in the interior housing. Check whether the model takes AA cells or a proprietary pack, and whether there's an exterior contact for jumping it when they die.
A locksmith fits and aligns the hardware. Network pairing is normally yours to finish.
The Four Measurements to Take Before You Buy
Tape measure, five minutes. Write the numbers down and check them against the lock's spec sheet before you order anything.
1. Door thickness
Measure the door edge, not the frame. Interior doors are typically 1-3/8 in., exterior doors 1-3/4 in. Most smart deadbolts cover 1-3/8 in. to 2 in., and some ship a spacer kit for reinforced slabs. Too thin and the through-screws bottom out before the halves clamp down. Too thick and neither the screws nor the cable reach.
2. Backset
Backset is the distance from the door edge to the center of the crossbore. On North American residential doors it is almost always 2-3/8 in. or 2-3/4 in. Many deadbolt latches adjust to cover both, but plenty are sold at a fixed size. Measure to the center of the hole, not the near edge, or you'll be off by more than an inch.
3. Crossbore diameter
The crossbore is the round hole through the face of the door, and the US residential standard is 2-1/8 in. Older doors, imported slabs, and some replacement doors come with 1-1/2 in. bores, which no standard smart deadbolt will cover. Enlarging one takes a hole saw run in a door jig, cutting partway from each face so the veneer doesn't blow out. Done freehand, it tears the face, and the escutcheon won't hide the damage.
4. Bore-to-edge spacing
The edge bore should be 1 in. across, with a mortise sized for a standard 1 in. by 2-1/4 in. faceplate. Then check the face has room for a smart lock body, which is far larger than a plain deadbolt ring. Standard center-to-center spacing between a knob bore and a deadbolt bore is 5-1/2 in. Where the two sit closer, or a glass lite, narrow stile, or applied molding crowds the bore, a tall keypad housing overhangs the trim and won't sit flat.
Retrofit Over Your Existing Cylinder vs a Full Lock Replacement
Smart locks split into two product categories, and your measurements route you to one of them.
A retrofit-over-cylinder unit replaces only the interior thumbturn. Your exterior cylinder, keyway, and keys stay exactly as they are, and a motorized adapter grips the thumbturn spindle and turns it from inside. It suits a deadbolt that's in good shape, a rental where you can't change exterior hardware, or a house already keyed alike. The conditions attached are real:
- The deadbolt must be single cylinder, key outside and thumbturn inside. A double-cylinder deadbolt gives the adapter nothing to grab.
- The thumbturn shape has to fit the supplied adapter. Oversized, decorative, and flush-mount turns often don't.
- The bolt must already turn smoothly with two fingers. A retrofit motor magnifies a sticky lock's problems, it never fixes them.
- You need clearance around the interior plate for a housing several inches across, including from any return wall.
A full-replacement smart deadbolt swaps out everything, bolt included, and needs all four measurements to line up. Choose it for an exterior keypad, a fresh cylinder, or a bolt that currently drags. It also lets you standardize keying while the door is apart, worth doing alongside any door lock repair the door already needed.
Doors a Standard Smart Deadbolt Will Not Fit
Some openings sit outside the bored-door standard entirely, and no amount of measuring changes that.
Mortise locks. The lock body lives in a rectangular pocket cut into the door edge, so there's no 2-1/8 in. crossbore to mount to. You need a smart mortise body sized to the existing pocket, or a motorized replacement for the mortise cylinder. Both are specify-and-order jobs, not shelf purchases.
Multipoint locks. Lift the handle and a gearbox throws three to five points at once: hooks, rollers, or shootbolts into the head and sill. A standard smart deadbolt turns one bolt and cannot drive that gearbox, so bolting one on gives you app control of a single point while the rest of the door stays disengaged. The real paths are a motorized euro cylinder that drives the existing gearbox, a replacement motorized gearbox, or a separate auxiliary smart deadbolt bored above or below the handle.
Euro cylinder doors. Composite, fiberglass, uPVC, and aluminum entries often use a profile cylinder passing straight through the door, sized in millimeters from the center fixing screw, commonly 92 mm between cylinder and handle spindle. That hardware has no US deadbolt prep and takes euro-format smart cylinders instead.
Handlesets. The deadbolt and the grip share one exterior escutcheon. Pull the deadbolt for a round smart lock and you're left with a mismatched plate, and on interconnected models, a linkage that no longer works.
Narrow-stile, glass, sliding, and storm doors. Aluminum storefront stiles, full-glass doors, patio sliders, and storm doors lack the material depth a bored deadbolt needs, and take purpose-built hardware.
Door material matters less than most people expect. Steel and fiberglass entries usually have an internal lock block and a standard bore, though some manufacturers still restrict their locks to wood doors on the spec sheet. Hollow-core interior slabs are the real problem, since there's often no solid block behind the bore for the screws to grip.
The Pre-Purchase Smart Lock Compatibility Checklist
Run these eight checks with a tape measure at the door. Each line routes you to outcome A, B, or C below.
| Check | How to take it | Passes if | If it fails |
|---|---|---|---|
| Door thickness | Tape across the door edge | 1-3/8 in. to 2 in., or the lock's stated range | Look for a thick-door or spacer kit, otherwise outcome C |
| Backset | Door edge to the center of the face bore | 2-3/8 in. or 2-3/4 in., matched by the lock or its adjustable latch | Any other figure means plugging and moving the bore: outcome C |
| Crossbore diameter | Straight across the round hole in the face | 2-1/8 in. | 1-1/2 in. or odd: enlarge with a door jig, or keep the existing lock and go outcome A |
| Edge bore and faceplate | Across the edge hole, then the plate itself | 1 in. bore, 1 in. by 2-1/4 in. faceplate | A different plate shape usually just needs re-chiseling: outcome B |
| Face clearance | Bore center to knob bore center, and bore to nearest glass stop or stile | About 5-1/2 in. between bores, lock body clear of glass and molding | Housing overhangs trim or glass: pick a compact body, or go outcome A |
| Existing lock type | Look at both faces and the door edge | Single cylinder deadbolt, key outside, thumbturn inside | Double cylinder: outcome B only. Mortise, multipoint, euro cylinder, handleset: outcome C |
| Door construction | Tap the face and inspect the edge | Solid wood, solid core, or steel and fiberglass with a lock block | Hollow core, full glass, narrow aluminum stile, slider, storm door: outcome C |
| Bolt and strike | Throw the bolt with the door open, then closed | Identical effort both ways, two fingers | Any added resistance closed: fix the strike or the door before buying |
Outcome A, retrofit over your existing cylinder. Your deadbolt is single cylinder, turns freely, and you'd rather not touch the exterior. Confirm interior clearance and thumbturn shape against the product page.
Outcome B, full-replacement smart deadbolt. All four measurements match a stock lock. Order it, and plan on 20 to 40 minutes with a screwdriver.
Outcome C, no standard smart deadbolt fits this opening. The prep has to be modified, or the door needs a different class of hardware. Have a locksmith look before you buy anything, since the fix depends on parts you can't identify from a product listing.
Why a Motorized Bolt Needs Tighter Strike Alignment Than a Manual One
This is the step most installs skip, and most smart lock complaints trace straight back to it.
With a manual deadbolt, your thumb and wrist supply whatever force the bolt needs. A misaligned strike just means you lean on the door and turn harder, and you may never register it as a fault. A motor has a fixed torque budget and no shoulder to lean with. When the bolt scrapes the strike, it stalls or drags, and you get:
- A bolt that stops half thrown, so the door reports as locked in the app while the frame is barely engaged
- Jam and obstruction errors, and auto-lock that fails silently overnight
- Battery life measured in weeks instead of months, because every cycle fights friction
- Stripped drive gears over a season or two
Test alignment before you mount anything electronic. Throw the existing bolt with the door standing open, where it should move with two fingers and no resistance. Close the door and throw it again. If the effort changes at all, the strike is off. Rub the bolt end with pencil graphite, close the door, throw the bolt, then read the scrape mark on the strike plate to see which way it's fighting.
Fixes, in the order a locksmith works through them: deepen or square up the strike pocket; reposition the strike plate, filling and redrilling the old screw holes so the new ones bite; fit a reinforced strike with 3 in. screws into the framing behind the jamb rather than the trim; shim the top hinge or run long screws through it to lift a sagging door back to square; plane a slab that has swollen or twisted. A door that binds seasonally will bind on the motor seasonally too, so solve it in the frame rather than in the app.
When to Handle It Yourself and When to Call a Locksmith
Do it yourself when all of these are true: the door already has a standard deadbolt prep, your four measurements match the spec sheet, the bolt throws freely with the door closed, and you're doing a straight swap or a retrofit over a healthy cylinder. That's a screwdriver, a tape measure, and half an hour.
Call a locksmith when:
- The door has no deadbolt hole and needs boring, particularly a metal-clad or fiberglass slab
- The crossbore is 1-1/2 in. or the backset is nonstandard, so a hole has to be enlarged or relocated
- The lock is mortise, multipoint, euro cylinder, or part of a handleset
- The bolt binds, the door sags, or the strike has to move
- You want the smart lock keyed alike with existing keys, or the house rekeyed at the same time
- It's a rental, an HOA-controlled entry, or a fire-rated door, where hardware changes can be restricted
- You're fitting several doors and want one key and one code system across all of them
Hire a deadbolt locksmith who bores, installs, and rekeys deadbolts and the drilling, jamb work, and keying happen in the same visit as the install, the part a general handyman quote usually leaves out. For what a single visit can cover, see residential locksmith services.
What Moves the Cost of a Smart Lock Install
On a door that's already bored, the lock itself is usually the larger share of the bill and labor the smaller line. No web page can quote your door, because the price turns on what has to happen before the lock goes on. What moves it:
- Whether the door is already bored, or needs a fresh crossbore, edge bore, and strike mortise
- Backset or bore mismatches that call for enlarging, plugging, or relocating a hole
- Strike and jamb reinforcement, worth adding while the plate is off anyway
- Door or hinge adjustment on a slab that sags or binds
- Mortise, multipoint, and euro cylinder work, which needs specified parts and lands well above a bored-door swap
- Number of doors, and whether they're keyed alike
- Programming and network setup, especially hub pairing or joining an existing system
- Minimum service call fees, plus after-hours and weekend rates
Ask for the quote split into hardware, labor, and door prep, then check it against locksmith cost ranges and service call fees before you agree to a number over the phone.
Smart Lock Installation FAQs
Will a smart lock fit any door?
No. A standard smart deadbolt needs a bored prep: a 2-1/8 in. crossbore, a 1 in. edge bore, a 2-3/8 in. or 2-3/4 in. backset, and a door 1-3/8 in. to 2 in. thick. Mortise, multipoint, euro cylinder, handleset, slider, and storm doors sit outside that standard.
Do I need a locksmith to install a smart lock?
Not for a straight swap on a door that already has a deadbolt and measurements matching the lock. Call one if the door needs boring, the bore or backset is nonstandard, the bolt binds, the lock is mortise or multipoint, or you want it keyed alike with existing keys.
How do I measure my door's backset for a smart lock?
Measure from the door edge to the center of the round hole in the face. It lands on 2-3/8 in. or 2-3/4 in., the only two common residential sizes here. Many latches adjust to cover both, but read the spec sheet rather than assuming yours does.
Can I put a smart lock on a double-cylinder deadbolt?
Not with a retrofit unit, since a double-cylinder deadbolt is keyed on both faces and has no thumbturn for the adapter to grip. A full-replacement smart deadbolt works, as it brings its own interior housing. Check fire code first, since keyed-both-sides locks on exit doors are restricted in many places.
Can I install a smart lock on a multipoint or French door?
Not a standard smart deadbolt. The gearbox throws three to five points when you lift the handle, and a bolt-on deadbolt turns only its own bolt. The real options are a motorized euro cylinder, a replacement motorized gearbox, or a separate auxiliary smart deadbolt bored above or below the handle.
How long does smart lock installation take?
Roughly 20 to 40 minutes on a door already prepped for a deadbolt, programming included. Boring a fresh door, enlarging a bore, moving a strike, or correcting a sagging slab adds an hour or more.
Take your four measurements first. If they match the spec sheet, the bolt throws freely with the door closed, and the radio suits your network, you're looking at a half-hour job. If anything is off, or the door is mortise, multipoint, euro cylinder, or a handleset, call a licensed local locksmith for a quote before you buy hardware you'll be returning.