Changing locks when moving house — what UK homeowners and tenants should know

Moving into a new home is one of the most common reasons people call a locksmith, and for good reason: you have no real way of knowing how many keys exist for your new front door, who holds them, or whether they were ever all returned by a previous occupant, tradesperson or estate agent. Changing the locks is one of the simplest and most effective security steps you can take in the first week of moving in.

It is easy to assume this is overly cautious, but keys get cut for house-sitters, cleaners, ex-partners and tradespeople over the years, and not every one of them is accounted for when a property changes hands. A locksmith can either replace the existing cylinder entirely or, in many cases, simply have it re-keyed to work with a new set of keys — a re-key is often quicker and cheaper than a full lock replacement, provided the existing lock is in good condition and of a reasonable standard to begin with.

This is also a good moment to check what standard your locks are actually built to. BS3621 is a British Standard for five-lever mortice deadlocks: to carry the BS3621 kitemark, a lock has to meet a set of tested security requirements and, on a final exit door, generally needs a key to open it from both sides once locked. It is not the same thing as a legal requirement — there is no law that says your front door must have a BS3621 lock — but it matters for a very practical reason: insurance.

A large proportion of UK home insurance policies specify that final exit doors must be secured with a BS3621-approved lock, or an equivalent standard, as a condition of cover for burglary. If your locks fall short and you are burgled, an insurer can refuse or reduce a claim on the basis that the policy condition was not met — even if the break-in did not happen through the door with the non-compliant lock. It is well worth checking your own policy wording rather than assuming your locks are covered, and asking a locksmith to confirm the standard of what is fitted, or upgrade it, when locks are changed after a move.

If your new home has UPVC or composite doors, the relevant standard is usually slightly different — these doors typically use a multipoint locking mechanism with a euro cylinder rather than a mortice deadlock, and the security rating that matters is TS007, not BS3621. We go into this in detail, including why cylinder choice matters so much for these doors, in our separate article on UPVC door lock problems.

For tenants, the position is more nuanced, and this is genuinely worth checking properly rather than assuming — tenancy agreements and landlord obligations vary, and this article is general information rather than legal advice. As a starting point, locks and their condition are typically the landlord's responsibility to maintain, and tenants are usually expected to ask permission before changing locks themselves, partly because a landlord, letting agent or emergency contractor may need access. If you have safety concerns, for example after losing keys or ending a relationship with someone who had a copy, raise it with your landlord or letting agent directly, or contact a service such as Citizens Advice for guidance specific to your tenancy.

One practical trade-off worth knowing about BS3621 mortice deadlocks is that, because they are designed to require a key on both sides, they can raise a fire-safety consideration: if the key is not readily accessible near the door, escaping quickly in an emergency becomes harder. It is common practice to keep a key on a hook close to the final exit door, precisely so that security and fire safety are not in conflict, and a locksmith can talk through the options if this is a concern in your particular property.

Front door locks are usually the main focus after a move, but it is worth doing a quick walk around the whole property at the same time — checking that window locks, French or patio doors, and any side gate or outbuilding access are in good working order, rather than assuming security only needs attention at the main entrance.

Whether you own or rent, it is worth keeping a simple record of when locks were changed, who carried out the work, and to what standard — useful if there is ever a dispute over a deposit, an insurance claim, or simply so a future buyer or tenant knows the history of the property's security.

A qualified locksmith can advise on which standard applies to your particular doors and fit locks that meet it properly. Our directory lists locksmiths covering towns and cities across the UK if you are looking for someone local to handle a move-in lock change.

Frequently asked questions