Most of the time, putting a smart lock on a door is a twenty minute job with a Phillips screwdriver. The rest of the time it turns into an afternoon of measuring, muttering, and a trip to the hardware store for a longer set of screws. The difference has very little to do with which lock you bought. It comes down to the door.
So before anything else, go and look at the door. Four measurements decide how your smart lock installation is going to go, and all four take about five minutes to check.
Start with the door, not the lock
Open the door and look at the edge, where the bolt comes out. You are checking for these things:
- Backset. The distance from the edge of the door to the centre of the round hole where the deadbolt sits. In US homes it is almost always 2 3/8 inches or 2 3/4 inches. Nearly every consumer lock ships with an adjustable latch that covers both, so this is rarely a problem, but it is worth knowing which one you have.
- Door thickness. Standard exterior doors are 1 3/4 inches. Interior and some older doors are 1 3/8 inches. Most locks handle anything from 1 3/8 to 1 3/4 inches out of the box. Thicker than that (solid wood doors, doors with added cladding, some security doors) and you need a manufacturer’s extension kit, which is worth ordering at the same time as the lock rather than three days later.
- Cross bore diameter. The big round hole through the face of the door. The standard is 2 1/8 inches. The smaller hole in the edge of the door, where the bolt slides, is 1 inch.
- What is on the door right now. A round single cylinder deadbolt above a handle is the easy case. A rectangular plate running down the edge of the door means a mortise lock. Several bolts firing at once when you lift the handle means a multipoint lock. Those last two are a different conversation, covered further down.
If your door has a standard bore and a normal deadbolt, you are in the easy 80 percent and you can stop worrying. If it does not, better to find out now than with the old lock already in a bag on the floor.
There are only three kinds of installation
Every smart lock on the market falls into one of three installation types, and the type matters more than the brand.
Retrofit: you only touch the inside
The lock replaces the thumbturn on the interior side and drives the deadbolt you already have. The exterior cylinder stays where it is, your keys keep working, and nothing about the outside of the door changes. August and SwitchBot built their reputations on this design.
No drilling, no new hardware on the street side, and it comes off in ten minutes leaving no trace. That last part is why it is the standard answer for anyone who does not own the door. If that is your situation, the renter’s guide to smart locks goes through it properly.
The trade off is that you inherit whatever is already on your door. A stiff, badly aligned deadbolt stays stiff and badly aligned, and now a small motor has to fight it. Retrofit locks fail on bad doors more often than they fail on their own.
Full replacement: the whole deadbolt comes out
The old deadbolt, bolt and strike plate all come out, and the new lock goes into the existing holes. Schlage, Yale, Kwikset and most keypad locks work this way. You get a keypad or a fingerprint reader on the outside, a proper new bolt, and hardware that was designed as one piece.
This is the version most people picture, and on a door with standard prep it is genuinely simple. You are not making new holes, you are swapping what sits in the ones already there.
Everything else
Mortise locks, multipoint locks, sliding patio doors, glass doors, and doors with no bore at all. These are real jobs, not screwdriver jobs. A mortise lock sits in a rectangular pocket cut into the edge of the door, common in pre war homes and older apartment buildings, and the number of consumer smart locks that fit one is small. Multipoint locks, usually on European style or newer patio doors, need a matching motorised unit rather than an add on.
None of this is impossible. It is just the point where paying a locksmith stops being an admission of defeat and starts being the sensible option.
What you actually need
For a standard replacement: a #2 Phillips screwdriver and a tape measure. That is the honest list. Add a pencil and a small level if you like things straight, and a hand drill if the frame screws need persuading.
Skip the cordless drill for driving the lock’s own screws. The plastic housings on the interior escutcheon crack easily and the torque is very hard to feel through a drill. Hand tight, then a quarter turn.
Replacing a standard deadbolt, step by step
- Take out the two long screws on the interior side of the old deadbolt. The inside and outside halves come apart. Keep the old lock somewhere safe until the new one has worked for a week.
- Take out the two screws holding the bolt assembly in the edge of the door and slide the bolt out.
- Take off the strike plate on the frame. Look at the hole behind it. If the paint or wood is scuffed on one side, your bolt has been rubbing, and that will matter later.
- Slide the new bolt in. Check the orientation: most bolts are stamped with an arrow or the word UP, and fitting one upside down is the single most common way to end up with a lock that jams on the second day. Adjust the backset first if yours is the collapsible kind.
- Fit the new strike plate. If the lock came with 3 inch screws, use them. They reach past the thin door jamb into the framing behind it, which is the difference between a lock that resists a kick and one that does not. This costs nothing and takes thirty seconds.
- Feed the exterior half of the lock through the door, making sure the tailpiece or spindle passes through the slot in the bolt. Hold it flush.
- Mount the interior half, start both screws by hand, then tighten them alternately a little at a time so the plate pulls up square. Overtightening one side first is what makes keypads sit crooked.
- Before the batteries go in, close the door and throw the bolt by hand. It should slide the whole way with no lifting, no shoving, and no resistance at the end of travel. If it does not, fix that now.
- Put the batteries in and let the lock run its calibration. Most locks learn the travel of the bolt on first power up, so the door needs to be closed and the bolt able to move freely for it to learn the right thing.
- Test it fifteen times, half of them with the door closed and half with it open, before you trust it with your keys on the other side.
Twenty minutes, give or take. If it is taking an hour, something in step 3 or step 8 is the reason.
Fitting a retrofit lock over the deadbolt you have
Shorter, but with one step people skip.
- Test the existing deadbolt first, with the door closed, by hand. This is the step people skip. If it needs a shove or a lift, the motor will need one too, and it does not have a shoulder.
- Unscrew the interior thumbturn and take it off. The exterior cylinder stays put.
- Fit the mounting plate over the existing tailpiece, using whichever of the supplied adapter plates matches your lock brand. Do not tighten fully yet.
- Check that the plate is level and the smart lock body will clear the door frame, the handle below it, and any weather stripping. Then tighten.
- Clip the lock body on, add batteries, and run the calibration with the door closed.
- Throw and retract it ten times from the app before you rely on it.
If your deadbolt is old, sticky or misaligned, fix it before fitting anything electronic to it. Twenty minutes with a chisel and a file on the strike plate now saves you a lock that mysteriously jams every third week in February.
A door with no hole at all
If there is no deadbolt on the door yet, you are doing carpentry before you do any smart lock installation. It needs a 2 1/8 inch hole saw for the face of the door, a 1 inch spade bit for the edge, a chisel for the bolt plate and strike mortises, and the paper template that comes in the box taped exactly where you want it.
It is doable, and plenty of people do it well the first time. But a hole saw wandering off centre on a door you cannot replace is a genuinely bad afternoon, and it is the one part of this job where a mistake is permanent. On a rental, do not do it at all. On a fire rated door, do not do it either, since cutting one voids its rating.
The things that actually go wrong
After the lock is on, almost every complaint traces back to one of five things, and only one of them is the lock’s fault.
The strike is not aligned. By far the most common. The bolt catches the edge of the strike hole instead of sliding into it, the motor stalls, and the app tells you the door is unlocked when it is jammed halfway. The fix is to file the strike hole slightly, or move the plate a few millimetres, so the bolt drops in without touching anything.
The door has moved. Wooden doors swell in humidity and sag on their hinges over the years. A lock that was fine in October starts stalling in March. Tighten the top hinge screws first, using longer screws into the framing, before you blame anything electronic.
The door is thicker than the lock expects. The screws will not reach, or they reach but the two halves never pull flush. Stop and order the extension kit rather than forcing it, because a lock mounted under tension will bind eventually.
The batteries are the wrong ones. Alkaline AAs are what these locks are designed for. Rechargeable cells sit at a lower voltage and lithium primaries can sit higher, and some locks read either as a fault or report a full charge right up to the moment they die. Check the manual and use what it says.
It works, but nothing else can see it. The lock itself is fine, but your phone loses it as soon as you walk away, or your voice assistant never finds it. That is a radio problem, not an installation problem, and it depends on whether the lock talks Bluetooth, Wi-Fi, Z-Wave, Thread or Matter, and whether you have the bridge it needs. Our guide to smart locks that work with Google Home covers what each one requires.
Doing it yourself or paying someone
For a straight deadbolt swap on a normal door, paying someone is hard to justify. It is two screws, a bolt, and a strike plate.
For a door with no existing bore, a mortise lock, a multipoint patio door, a metal door, or a fire rated door, a locksmith is worth the money. Typical US pricing runs somewhere around 80 to 200 dollars in labour for a straightforward installation, more if the door needs prep work, and rates vary a lot by city and by how urgently you need it done. Get the quote confirmed against a photo of your actual door before booking, because the price of a bore job and the price of a swap are not close.
One more case for hiring out: if you rent, and your lease requires the original hardware to be reinstated when you leave. Having someone competent take it off and put the old lock back is cheaper than losing a deposit.
Common questions
How long does it take?
Fifteen to thirty minutes to swap a deadbolt, ten to fit a retrofit lock over one that already works. An hour or more if the door needs new holes cut, and longer if you are doing that carefully, which you should be.
Add another ten minutes for the app: creating the account, pairing, updating the firmware, and setting up whoever else needs access.
Do I need to remove my existing lock?
Only for a full replacement. Retrofit locks keep the existing deadbolt and cylinder entirely, which is also why your old keys keep working and why nothing changes on the outside of the door.
Will it still work if the batteries die?
Depends on the lock. Models that keep a keyway on the outside can always be opened with the physical key. Keypad only models usually have contacts on the underside for a 9V battery held against them, enough to get you in and turn the lock once. Check which of the two you are buying before you need to find out, and keep a physical key somewhere outside the house either way.
Can I install one on a rented apartment door?
Usually yes, if you choose a retrofit model that only replaces the interior thumbturn, and if you keep the original parts. Building doors and shared entrances are a different matter and normally need the landlord’s agreement. The renters guide goes through what is reversible and what is not.
The short version
Measure the door before you buy the lock. Choose retrofit if you cannot change the outside of the door, full replacement if you can. Use the long screws in the strike plate. And test the bolt by hand, with the door closed, before you ask a small motor to do it for you.