Why You Should Change the Locks Before Moving In (and How)

The keys handed to you at closing are almost never the only keys that exist. Over the years a house collects copies the way a junk drawer collects spare batteries: one to a neighbor for watering plants, one to a dog walker, one a teenager made and never returned, a couple cut for contractors, maybe a hide-a-key tucked under a flowerpot that nobody mentioned. You have no way to count them and no way to call them back. That is the whole case for resetting entry access on day one, before your furniture and your family are inside.

This guide stays narrow on purpose. It covers keyed and coded entry to the home itself: front and back doors, side and garage walk-in doors, gates, and the mailbox. It does not cover the broader move-in inspection (see our guide on what to inspect and fix before you move in), transferring or canceling a home-security alarm system (covered separately), childproofing cabinet and door latches for safety, or who to notify about your address change. Those are their own jobs. Here, the question is simple: who can still walk in, and how do you shut that down.

Why the Previous Owner’s Keys Are a Real Risk

The risk is not that the seller is plotting against you. The risk is that access spreads quietly and never gets cleaned up. A typical resale home has changed hands before, been rented or listed, hosted open houses, and been visited by service people who needed to get in. Real-estate professionals routinely note that you simply cannot know how many copies of the existing keys are circulating, which is why changing access is a standard first move-in task rather than a paranoid one.

New construction is not automatically safe either. Builders, framers, painters, inspectors, and the listing agent may have all used a construction key or a lockbox during the build, and those locks are sometimes set to a builder’s “construction keying” that you are expected to finalize. Treat a brand-new home the same way you treat a resale: assume access has been shared until you reset it yourself.

There is also a quieter, practical reason to act early. If an old key still works and someone lets themselves in without forcing a door or window, there may be no physical sign of a break-in at all. Insurers often look for evidence of forced entry when they evaluate a theft claim, so a door that was opened with a legitimate-looking key can complicate matters. Coverage terms vary by policy and state, so confirm what your specific homeowners or renters policy requires; the point here is only that “no broken window” is not the same as “no one got in.”

The cleanest rule of thumb: change the locks when you take possession, ideally before you move anything valuable inside. If that timing is not realistic, do it within the first few days. Every day you wait is a day the unknown copies still work.

Rekey vs. Replace vs. Smart Lock: What Each Solves

You generally have three ways to reset access, and they solve different problems.

Rekeying keeps your existing lock hardware but changes the inside so old keys stop working. A standard residential deadbolt or knob is a pin-tumbler lock: a row of small pins has to line up at a “shear line” for the cylinder to turn, and the cut of the key is what lines them up. Rekeying swaps those pins for a new set matched to a new key, which instantly voids every old key. Schlage’s own rekeying guidance describes this as repinning the cylinder so the lockset works with a single new key, and notes that a rekeying kit can set several locks in the home to one matching key. Rekeying is the move when your existing locks are in good shape and you mainly want the old keys to die.

Replacing means removing the whole lock and installing a new one. You choose replacement when the existing hardware is worn, damaged, mismatched, low quality, or simply old, or when you want to upgrade the deadbolt grade or the finish. It is more involved than rekeying because you are swapping the physical lock, not just its pins, but it gives you a clean, known-history lock with brand-new keys.

Smart locks (keypad or app-connected) change the question from “who has a key” to “who knows a code or has access in the app.” They let you hand out and revoke entry codes without cutting metal, which is genuinely useful when you expect cleaners, dog walkers, or guests. They are not automatically more secure than a good deadbolt, and they add batteries and electronics to maintain, but for ongoing access management they are hard to beat. Many keypad models still include a physical key as a backup, so the rekey-or-replace logic above applies to that backup cylinder too.

One compatibility note worth knowing before you buy: locks from different manufacturers generally cannot be rekeyed to share a key, so if your goal is one key for the whole house, plan around a single brand.

Don’t Forget These Access Points (Back Doors, Garage Entry, Gates, Mailbox)

People reset the front door and stop. Walk the perimeter and you will usually find more.

Every exterior door, not just the front. Back doors, side doors, basement walk-outs, and the people-door from the garage into the house all need the same treatment. The garage-to-house door is a common blind spot because it feels “interior,” but it is an exterior-grade entry point.
The garage itself. Reset the keyed walk-in door as above. Garage-door opener remotes and keypad codes are part of your services-and-utilities setup rather than keyed entry, so handle those in that context, but do not skip the walk-in door’s lock.
Gates, sheds, and outbuildings. Padlocks and gate locks on fences, side yards, sheds, and detached garages are access too. Cut off the old keys there the same way.
The mailbox. If you have a private, homeowner-owned curbside box, USPS does not provide or replace its lock; you install or change that lock yourself, or ask the seller for the key. If your address uses a USPS-managed centralized or cluster box unit, the responsibility is different. USPS guidance directs residents to request keys or a replacement from the appropriate party rather than prying the box open, and because the Postal Service generally does not keep duplicate keys, a lost-key situation on a USPS-controlled box typically means the lock is replaced rather than re-cut. Sort out who currently holds the mailbox key as part of resetting access; for the address-change paperwork itself, see our separate guide.

Make a quick written list of every locking point as you walk the property, then check each one off as you reset it. It is easy to overlook a side gate or a basement door until you are standing there a week later realizing it still opens with a key you never accounted for.

DIY Rekeying vs. Calling a Locksmith

Both paths work; the right one depends on your locks, your tools, and your comfort level.

Doing it yourself is realistic for common residential deadbolts and knobs. Manufacturer rekeying kits are sold for specific lock brands and include the pins and tools to repin the cylinders to a new key, and some brands sell keyed-alike sets so several new locks already share one key out of the box. Certain modern locks are designed for fast at-home rekeying with the original key and a small learn tool, no full disassembly required. If you go this route, match the kit to your exact lock brand and model, work over a tray so you do not lose the tiny pins and springs, and test the new key from both sides of the door before you call it done. Buying new locks outright and installing them is also well within DIY range if you can use a screwdriver and follow the included template.

Calling a locksmith makes sense when you have higher-security or commercial-grade cylinders, an unusual or older lock, a lot of doors to do at once, or you simply want it handled correctly and quickly. A professional can rekey in place or replace hardware, get every door onto one key, and confirm everything functions. Costs vary by region, by how many locks you have, and by whether you rekey or replace, so get a clear quote up front; this guide does not quote prices because they differ too much to state responsibly. When you hire someone, it is reasonable to ask for identification and confirm they are a legitimate, insured locksmith before you let them work on your doors.

A middle path many people take: rekey the existing doors yourself or via a locksmith to kill the old keys fast, and replace only the specific locks you actually want to upgrade.

Resetting Codes: Keypads, Smart Locks, and Spare Keys

If your new home already has a keypad or smart lock, changing the metal keys is only half the job. Whatever codes the previous occupant set are still live until you clear them.

Start by wiping the slate. For most keypad and smart locks, the manufacturer documents two approaches: delete individual user codes one at a time, or perform a factory reset that erases all programming and returns the lock to its defaults so you can set it up fresh. Schlage, for example, publishes model-specific programming guides and support articles covering exactly this, including how to factory-reset a connected model and then reprogram it. After a reset, you re-enter the default codes from the lock’s own documentation and create new entry codes that only you know. Keep the lock’s default programming or access code somewhere safe, because you will need it to make future changes.

A few habits worth building from day one:

Set a fresh, non-obvious entry code. Avoid the address number, repeated digits, or anything the previous owner might have used.
Use separate codes for separate people where the lock supports it, so you can revoke one without disrupting everyone.
For app-connected locks, take over the account. Make sure the lock is registered to you, remove any prior owner’s account or shared access, and update the app password. A reset cylinder does nothing if someone still has remote control in an app.
Track your spare keys. Decide how many copies you actually need, label where each one lives, and avoid the classic hide-a-key under the mat or in an obvious fake rock. A spare you cannot account for is the same problem you just solved with the old owner’s keys.

Once every door is rekeyed or replaced, every secondary access point is handled, and every code is reset, you have done what you set out to do: you, and only the people you choose, can get into your home.

This article is general information, not legal, security, or insurance advice. Lock options, mailbox-key procedures, and what your homeowners or renters insurance requires can vary by location, hardware, and policy, so verify current details with the official sources below and with your own provider before you rely on them.

Sources

USPS, Postal Operations Manual / Handbook PO-632, “3-2 Mailbox Locks and Keys”, https://about.usps.com/handbooks/po632/po63203002.htm
USPS, Notice 11, “Tips for Postal Customers with Centralized Mailboxes”, https://about.usps.com/notices/not11/not11.htm
USPS.com FAQ, “Locked Mailboxes and Mailbox Keys”, https://faq.usps.com/s/article/Locked-Mailboxes-and-Mailbox-Keys
Schlage, “Rekeying Quick Start Guide” (P513-325), https://www.schlage.com/content/dam/sch-us/documents/pdf/installation-manuals/P513-325.pdf
Schlage, “Smart Lock Programming Guides”, https://www.schlage.com/en/home/support/programming-guides.html
Schlage Residential Support, “Factory Reset a Schlage Encode Lock”, https://schlage-res.zendesk.com/hc/en-us/articles/34130652492436-Factory-Reset-a-Schlage-Encode-Lock