A smart lock is a motor, a battery and a small radio bolted onto hardware that was already in the door. The app is the easy part. What decides whether it still works next February is the door it went onto, and on a lot of Toronto houses that door has been quietly out of square for years.

Most smart lock complaints that turn into a service call are not software problems. The bolt binds, the motor stalls halfway, the batteries die in six weeks, the lock reports a jam every third time. Nearly all of it traces back to the door, the frame or the strike plate.

What a smart lock actually asks of the door

A key gives you leverage, and your hand reads resistance without thinking about it. You feel the bolt catch, you lift the door slightly on the handle, you turn a little harder, it goes. A motor does none of that. It turns until it hits a preset torque limit, then stops and reports a fault.

That is the entire difference. A door that was merely stiff with a key becomes unreliable the moment a motor is doing the turning. So before anything else, the test is simple: with the door standing open, throw the deadbolt by hand. It should move with one finger, smoothly, all the way out. Then close the door and do it again. If the second one is harder than the first, the door and the frame are not lined up, and no lock will fix that.

Backset, bore and the hole that is already there

Smart deadbolts are built around the two standard North American backsets and a standard bore. Older Toronto doors, particularly solid wood ones in pre-war houses, were often drilled by hand to whatever suited the hardware of the day. A retrofit onto one of those usually means enlarging or relocating the bore, and on a door with a narrow stile there may not be enough material left to do it safely.

Doors with a multi-point lock are their own category. The smart cylinder options that drive a multi-point gearbox are far narrower than the consumer shelf suggests, and a standard smart deadbolt is not one of them. Changing a lock on an existing door is straightforward when the prep matches and genuinely involved when it does not, and that is worth knowing before the box is opened.

The strike plate is where most of them fail

The bolt needs clearance in the strike. Not a lot, but some, and in every direction. When a door has settled, the bolt starts catching the lower edge of the strike hole. With a key you never notice, because you are lifting the handle slightly as you turn. The motor just pushes straight into the edge of the plate and stalls.

Enlarging the strike hole is the common field fix, and sometimes it is the right one. But if the bolt has moved more than a few millimetres, the strike is a symptom. The door has dropped on its hinges, or the frame itself has moved, and the honest repair is at the frame. Hinge screws that no longer bite, a jamb that has split behind the strike, a sill that has settled under one side of the opening all show up this way. Frame and jamb work is unglamorous and it is usually what makes the lock behave.

Toronto winter is the real test

Batteries in January

Alkaline cells lose capacity in the cold, and an exterior deadbolt on a north-facing door spends January sitting close to outdoor temperature. A lock that reports plenty of charge in October can drop to a low-battery warning in a single cold snap. That is normal battery chemistry, not a defective lock. It matters because a motor running on a weak battery produces less torque, which means the first thing a cold battery does is make a slightly stiff bolt into a stalled one.

Lithium cells hold up considerably better in the cold than alkaline. Whatever the lock takes, knowing where the mechanical key override is, and having one that actually works, is the part people skip.

Frost, swelling and seasonal movement

Wood doors take on moisture and give it back with the seasons. Steel and fibreglass doors move far less, but their frames still do, and so does the house. A door that fits in August is tighter in November. Add a weatherstrip that has gone hard in the cold and now resists compression, and the latch has to pull the door in against real force.

A motorised bolt cannot pull a door closed. If the door is not already sitting flush in the frame when it tries, it jams. The fix is the door and the seal, not the lock.

Retrofit or replace the whole lock

Retrofit units keep the existing exterior cylinder and deadbolt and drive the thumbturn from inside. The advantage is real: the mechanical lock is unchanged, your keys still work, and if the electronics fail the door still locks. The limitation is that they inherit whatever the existing deadbolt does, binding included.

Full replacement gives you a new bolt, a new strike and hardware designed for a motor. If the existing lock is old, worn or mismatched to the door, this is usually the better outcome. It is also the option that exposes any prep problems in the door, which is a reason to look at the door first rather than after.

Connectivity is a smaller question than it looks

Bluetooth-only locks talk to a phone standing at the door. Wi-Fi or hub-connected locks can be checked and operated remotely. Which you want depends on whether you actually need to let someone in while you are not home. What matters mechanically is that the radio does not change the motor, the bolt, or the door. A connected lock on a binding door is a binding door that now sends you notifications about it.

What to sort out before buying

• Throw the deadbolt by hand, door open and door closed. Any difference is an alignment problem.
• Check the hinge screws. A door that has dropped is a door that will bind.
• Look at the strike hole for bright scrape marks, which show you exactly where the bolt is hitting.
• Confirm the backset and bore match what the lock expects, and check the door stile is wide enough.
• Press the door closed by hand and see whether the weatherstrip is fighting it.
• Decide where the mechanical key lives.

None of that is exotic, and most of it takes ten minutes. The point is that a smart lock is a precision device being asked to operate a mechanism that was built to tolerate a human hand. Close the gap first and the lock is boring, which is what you want from a lock. Skip it and you have bought a notification system for a door that does not shut properly. If the door is already fighting you, sorting the door out is the step that makes everything after it work.

Frequently asked questions

Can a smart lock go on any door?

No. It needs a compatible backset and bore, enough stile width, and a door that closes without binding. Multi-point locks and some older hand-drilled doors need different hardware or prep work.

Why does my smart lock jam only in winter?

Two things stack up. Cold reduces battery output, so the motor has less torque, and seasonal movement plus a stiffened weatherstrip makes the bolt harder to throw. Either alone might pass. Together they stall the motor.

Will a retrofit smart lock fix a sticking deadbolt?

It will not. A retrofit drives the existing thumbturn, so it inherits the existing problem and usually makes it more obvious, because a motor has no judgement about resistance.

Does a smart lock need a new strike plate?

Often yes, and not only for alignment. A deeper or reinforced strike with longer screws into the framing is worth doing whenever the lock is off the door anyway.

What happens if the batteries die completely?

Most locks keep a mechanical key override, and many have external contacts that let you hold a battery against them to power the lock briefly. Both are worth testing once when the lock is new rather than at the door in the dark.