How to Change the Locks in Your New Home

Why it matters

Changing the locks is the single most important step in securing a new-to-you property. When you purchase a resale home, you receive a set of keys at closing, but you have no way of knowing how many duplicates exist. Previous owners, contractors, neighbors, and real estate agents may all have keys to your front door. Replacing or rekeying the locks resets your home’s security to zero, ensuring that only you and your family have access. Beyond physical security, updating locks allows you to move all entry points to a single "one-key" system or upgrade to smart technology, which can improve your daily convenience and provide a digital audit trail of who enters your home.

How often

Changing locks is not a recurring maintenance task like replacing HVAC filters, but it should be performed during specific life events:

• Immediately upon moving in: This is non-negotiable for resale homes.
• After losing a key: If a labeled key or a key attached to your wallet is lost, replace the locks immediately.
• After a breakup or roommate move-out: If the departure was not amicable, changing the locks provides peace of mind.
• Every 7–10 years: Mechanical locks eventually wear out. If you notice the key sticking, the cylinder wiggling, or the bolt becoming difficult to turn, the internal pins are likely degraded.

What you need

Before you head to the hardware store, identify whether you want to rekey (keep the existing hardware but change the internal pins) or replace (install entirely new knobs and deadbolts).

Tools for replacement:

• Phillips head screwdriver: Most modern locksets use standard #2 Phillips screws.
• Tape measure: To measure the "backset" (the distance from the edge of the door to the center of the lock hole).
• Flathead screwdriver: Useful for prying off old strike plates.
• Hammer and chisel: Only needed if the new strike plate or latch has a different shape than the old one.

Supplies:

• New locksets/deadbolts: Look for ANSI Grade 1 (highest security) or Grade 2 (standard residential) ratings.
• Lubricant: Graphite powder or silicone-based spray for the new mechanism.

Step-by-step: How to replace a deadbolt

Most homeowners choose to replace the entire lockset to ensure all hardware matches and functions like new.

1. Measure the backset: Measure from the edge of the door to the center of the bore hole. It will typically be either 2-3/8 inches or 2-3/4 inches. Most modern locks are adjustable to fit both, but verify this on the packaging before buying.
2. Remove the old hardware: Open the door. Unscrew the two long screws on the interior side of the deadbolt. Pull the interior and exterior halves of the lock apart. Remove the two screws on the edge of the door to pull out the old latch/bolt.
3. Install the new bolt: Slide the new bolt mechanism into the hole on the edge of the door. Ensure the "up" marking is facing correctly. If the bolt doesn't reach the center of the bore hole, twist the mechanism to adjust the backset length. Fasten it with the provided wood screws.
4. Insert the exterior cylinder: Align the torque blade (the flat metal bar) so it passes through the center of the bolt mechanism. The keyhole should be upright.
5. Attach the interior plate: Align the interior turn-piece with the torque blade. Thread the two long mounting screws through the interior plate, through the bolt mechanism, and into the exterior housing.
6. Tighten and test: Tighten the screws by hand until snug. Do not over-torque with a power drill, as this can misalign the internal gears. Test the lock with the door open first, then test it closed to ensure the bolt aligns with the hole in the door frame.
7. Replace the strike plate: Remove the old strike plate from the door frame and install the new one provided with the kit. Use long (3-inch) screws that reach into the wall stud for maximum kick-in resistance.

When to call a pro

While replacing a standard deadbolt is a straightforward DIY task, you should call a professional locksmith in the following scenarios:

• Mortise Locks: If your home has large, rectangular lock boxes integrated into the side of the door (common in older homes), these are complex and difficult for a DIYer to replace.
• Rekeying: If you like your existing high-end hardware (like Baldwin or Emtek) and just want to change the key, a locksmith can rekey the cylinders for much less than the cost of new high-end hardware.
• Misaligned Doors: If your door has sagged and the bolt doesn't line up with the frame, a locksmith can shim the hinges or adjust the strike plate professionally.
• Smart Lock Integration: If you are uncomfortable with wiring or Bluetooth/Z-Wave syncing for high-tech entry systems.

Safety

• One Exit at a Time: Never take apart all your exterior locks at once. Work on one door at a time so the house remains secure if you need to run to the store for a forgotten tool.
• Check the Fire Code: Ensure your new deadbolts use a thumb-turn on the interior. "Double-cylinder" locks (which require a key on both sides) can be a fire hazard, as you cannot exit quickly in an emergency without a key. Some local jurisdictions ban these.
• Reinforce the Frame: The lock is only as strong as the door frame. Always use 3-inch screws for the strike plate to anchor it into the house framing rather than just the decorative trim.

Cost

DIY Replacement:

• Standard Deadbolt: $25 – $50 per door.
• Electronic/Smart Lock: $120 – $300 per door.
• Tools: $0 (assuming you own a screwdriver).

Professional Locksmith:

• Service Call Fee: $75 – $150 (the cost just for them to show up).
• Labour for Rekeying: $20 – $50 per cylinder.
• Labour for Replacement: $50 – $100 per lock plus materials.
• Total for a 3-door home: Expect to pay $200 – $450 depending on your location and the quality of the locks chosen.