Locks explained
Smart Locks: Keypad, Fingerprint and App Entry Explained
A smart lock opens by code, fingerprint, phone app or fob, as well as or instead of a key. Some fit over your existing lock on the inside; others replace it. Look for the BSI Kitemark for smart locking devices, keep the cylinder graded, and check with your insurer. Fitting is charged by time, at £65 to £85 an hour (MLA price list, Checkatrade and Bark).
What kinds of smart lock are there?
- Keypad locks: a code entered on the outside. Some also take a card or fob. - Fingerprint locks: a reader on the outside that stores a set of prints. - App locks: controlled from a phone over Bluetooth, often with a hub for remote access and a log of who came in. - Combination locks: push-button locks, some with no battery at all, common on gates and internal doors.
Most combine two or more of these, and most keep a key override for emergencies. The searches "digital door lock" and "smart lock" cover the same ground, and the choice between them is really about how the lock fits your door.
Retrofit or replacement: which fits your door?
A retrofit smart lock clamps over the thumb turn of an existing euro cylinder on the inside. The outside of the door looks unchanged and the key still works, so the door's security is still the cylinder's grade. It suits renters and anyone who may want to remove it later, though it usually needs a thumb turn cylinder. A replacement smart lock swaps the cylinder, or the whole lock body, for an electronic unit with a keypad or reader outside. It changes the door's security, so its own grade matters. Multipoint uPVC and composite doors take both kinds; timber doors with mortice locks often need a different model or more work.
Which standard should a smart lock meet?
BSI runs a Kitemark for smart residential locking devices, built on TS 621, a technical standard written by the Door and Hardware Federation. It tests both the physical lock and its electronics, including resistance to attack and the device's encryption. If a retrofit lock leaves your existing cylinder doing the physical work, that cylinder should still be TS 007 3 star or Sold Secure SS 312 Diamond. A smart lock without any mark is not necessarily weak, but you have no independent test to rely on, and no standard to quote to an insurer.
What might your insurer say?
Home insurance policies were written around keyed locks, and many still name BS 3621 for timber doors or a graded cylinder for uPVC doors. A smart lock that replaces those may not match the wording, however well it is made. Before you buy, ask the insurer whether the lock you have in mind meets the policy, and keep the reply. Ask too how a claim would be handled if a code was shared or a phone was stolen. Wording varies by insurer, and this site has not checked policies one by one.
What about batteries, and when do you call a locksmith?
Most smart locks run on standard batteries and warn through the app or a light well before they go flat. Many have an emergency power point outside or a key override, so keep the key somewhere you can reach it. Fitting is charged by time: £65 to £85 an hour in the daytime (MLA price list, Checkatrade and Bark). A retrofit is short work; a replacement lock on a multipoint door can mean a new cylinder or gearbox, which the same sources price separately. Call a locksmith if the lock jams, if the door needs adjusting before any smart lock will run smoothly, or if you are locked out.
Common questions
Will a smart lock work if the battery dies?
Most give warnings well in advance, and many have an external power point or a key override. Check how your model handles a flat battery before relying on it as your only way in.
Can I fit a smart lock in a rented home?
A retrofit that clamps over the inside thumb turn leaves the outside of the door unchanged, which suits renters. Most tenancies still need the landlord's agreement for any change to the locks, so ask first.
Is a smart lock more secure than a key lock?
Not automatically. The physical lock still matters most. Look for the BSI Kitemark for smart locking devices, and make sure any cylinder behind a retrofit lock is TS 007 3 star or SS 312 Diamond.
Can a locksmith fit a smart lock I bought online?
Many will, charging by the hour. Send the model name first so they can check it suits your door and whether a different cylinder or gearbox is needed to make it run smoothly.