A smart lock that is fitted well is invisible and reliable. One that is fitted onto a door that was not quite right eats batteries, jams, and reports locked when it is not. Almost every long-term smart lock complaint traces back to something that should have been checked before buying.
The short answer
Before ordering anything, check three things: what type of lock your door has and whether the model supports it, whether the door closes and locks freely by hand with the door shut, and whether the door thickness is within the lock’s range. A door that is stiff to lock by hand will be worse with a motor, and no smart lock fixes a misaligned door.
The pre-purchase checks
- Lock type. Euro cylinder, mortice, rim cylinder, multipoint and deadbolt are all different, and smart locks are made for specific types. Multipoint locks, common on uPVC and composite doors, need a model made for them.
- Door thickness. Every lock specifies a range. Composite and uPVC doors are often thicker than the wooden doors a lock was designed around.
- Backset measurement. The distance from the edge of the door to the centre of the cylinder. Get this wrong and the lock will not fit.
- Does it lock freely by hand? With the door closed, turn the key. Any stiffness is the motor’s problem later. Fix the alignment first.
- Is there room inside? The interior unit is bulky. Check it clears the door frame, any furniture behind the door, and the door opening fully.
- Wi-Fi at the door. Front doors are usually far from the router. Check the signal there before assuming remote features will work.
Test the door by hand first
Open the door and turn the lock. Then close it and turn the lock again. Any extra resistance with the door closed means the strike plate is misaligned, and that must be fixed before fitting anything motorised.
Fix the alignment now, not later
Mark where the bolt hits with pencil lead on its end, then adjust or enlarge the strike plate so the bolt passes freely. Tighten the hinge screws while you are there, since a dropped door is the usual underlying cause.
Measure the door thickness and backset
Write both down and check them against the lock’s specification before ordering. These are the two measurements that decide whether it fits at all.
Check the Wi-Fi signal at the door
Stand at the door with the door closed and run a speed test. Front doors are often at the edge of coverage. If the signal is poor, plan for a hub, a mesh node nearby, or a lock that uses a low-power protocol through a hub rather than Wi-Fi directly.
Check what is behind the door
The interior unit is substantially thicker than a normal thumb turn. Open the door fully and check it clears the wall, and check nothing hangs on the back of the door in its way.
Decide about the key
Some smart locks retain the existing cylinder so keys keep working; others replace it. If other people have keys, or you want a physical backup, that decides which type to buy.
Fit it with the door open
Do the whole installation with the door open so nothing can lock you out mid-job. Run the calibration routine before closing the door for the first time.
Test thoroughly before relying on it
Lock and unlock twenty times from the app, from the keypad, and by hand, with the door closed. If it hesitates or retries even once, go back to the alignment.
Never fit or test a smart lock with the door closed and no key accessible. Keep a physical key outside the door or with someone else until you have confirmed the lock works reliably. Being locked out by a half-configured smart lock is a genuinely common and entirely avoidable experience.
Rented homes and shared doors
Check your tenancy agreement before changing a lock. Many require landlord permission, and some require the original lock to be reinstated when you leave. Locks that fit over the existing thumb turn without replacing the cylinder are the usual answer for rentals, because they leave the outside of the door and the existing keys untouched.
For a shared entrance in a block of flats, a smart lock on the communal door is generally not yours to fit, and the flat door is where these are practical.
Use lithium batteries from the start, particularly on an exterior door. They hold voltage far better under the brief high-current pulses a lock motor draws, and they perform dramatically better in cold weather, which is exactly when a lock is most likely to fail.
After fitting
- Run the calibration routine, and run it again after any adjustment to the door.
- Set the auto-lock delay long enough that the door is genuinely closed before the bolt fires.
- Fit a door sensor if the lock supports one, so auto-lock only triggers on a properly closed door.
- Keep a physical key somewhere accessible outside the house.
- Note the emergency power method: many locks have external contacts where a battery can be held to provide enough power to open them.
- Check battery level monthly for the first few months to learn how fast it actually drains.
Will a smart lock fit my door?
It depends on the lock type, the door thickness and the backset. Measure all three and check them against the specification before ordering, since these are the things that make a lock physically incompatible.
Do I need to fix my door before fitting one?
Yes. If the door is stiff to lock by hand with the door closed, a motor will struggle far more than your wrist does. Adjust the strike plate first.
Can I fit a smart lock in a rented home?
Check your agreement first. Locks that fit over the existing thumb turn without replacing the cylinder are the usual answer, since they leave the outside of the door and existing keys untouched.
What happens if the batteries die while I am out?
Most locks have a physical key override, and many have external contacts where you can hold a battery for emergency power. Find out which yours has before you need it.
Will my existing keys still work?
Depends on the model. Some retain the existing cylinder and keys; others replace it. Decide this before buying if other people hold keys.
The bottom line
Test the door by hand with it closed before you order anything, because a stiff door is the root of nearly every long-term smart lock problem and fixing the strike plate is a twenty minute job. Measure the thickness and backset, check the Wi-Fi at the door, and fit the whole thing with the door open. Keep a key outside until you have tested it properly.
