Before choosing fingerprint access, a keypad or phone control, start with your door. The existing lock mechanism, door measurements and available space will help you narrow down the options.
This guide covers five checks to make before buying. Always compare your findings with the installation guide for the exact model you are considering.
1. Identify your existing lock
Open the door and look at the hardware on both faces and along the door edge.
A separate deadbolt above a handle
Many North American entry doors have a deadbolt above a separate knob or lever. The deadbolt provides the main locking function; the lower handle operates a spring latch for everyday opening and closing. A replacement smart deadbolt may suit this arrangement, subject to its installation requirements.
A lock built into the handle
A locking knob or lever with a spring-loaded latch is a different mechanism. Choose a smart lock designed for that arrangement and the intended use of the door. A smart lever is not automatically a substitute for a separate deadbolt.
A mortise or multipoint lock
A mortise lock uses a lock case fitted into a pocket in the door. A multipoint system locks at several positions along the door edge. These need their own compatibility checks; do not assume a standard replacement smart deadbolt will fit.
2. Measure the door and check its openings
Compare these measurements with the selected model's installation guide:
- Door thickness: measure where the lock will mount, including any additional plates that affect the installation.
- Backset: measure from the door edge to the center of the main lock hole.
- Face bore: check the diameter of the main hole through the face of the door.
- Edge bore: check the diameter of the smaller hole through the door edge for the bolt or latch.
Older doors may have different openings from newer doors. Common North American measurements are useful reference points, not a guarantee that a particular lock will fit.
Look at the door-edge mounting style
Some bolts use a faceplate secured to the door edge with two screws. Others use a round drive-in collar seated in a circular opening. Check that the chosen lock includes or supports the mounting arrangement your door requires. Do not assume the old bolt or collar can be reused with a new smart lock.
Some measurements are hidden by existing hardware. Check available documentation first. If identifying them requires removing the lock and you are unsure how, ask an installer for help.
3. Check the space around the lock
Matching holes are only part of the check. The new lock needs room to sit flat and operate on both sides of the door.
- Check the distance between the deadbolt and the handle below.
- Look for raised trim, molding or glass close to the mounting area.
- Check clearance from the door frame and any outer storm or screen door.
- Allow space to access and remove the interior battery cover.
Compare the exterior and interior housing dimensions with the available space. Consider whether the new mounting plates will cover marks left by the old hardware.
4. Make sure the door locks smoothly
Try the existing lock with the door open, then closed. Do you have to lift, push or pull the door before the deadbolt will turn? Does the bolt rub against the strike plate on the frame?
The faceplate sits on the door edge. The strike plate sits on the door frame and surrounds the opening that receives the bolt or latch. These are different parts, and strikes for different lock mechanisms are not automatically interchangeable.
A motorized lock does not correct a sagging door or a misaligned strike. The bolt should extend and retract smoothly without forcing the door into position. Have binding or alignment problems checked before replacing the lock.
5. Consider where the door is installed
An interior bedroom door, a sheltered front door and an exposed garden gate present different conditions. Check the model's intended use, operating temperatures and weather-resistance information, including which components those specifications cover.
A weather-resistant exterior keypad does not mean the interior battery housing can be exposed to rain. Sliding doors, narrow-frame doors and garage overhead doors also need different hardware from a typical residential hinged door.
For doors with special requirements, including labeled fire doors and garage-to-home connecting doors, confirm the permitted hardware and installation requirements before making changes.
Not sure? Ask LNDU before you order
Contact LNDU with the model you are considering and:
- A photo of the existing lock from outside.
- A photo from inside, including the handle and surrounding space.
- A photo of the door edge showing the bolt or latch.
- Your available measurements and a brief description of the door's location and weather exposure.
Keep house numbers, access codes and other private information out of the photos. We can help identify what needs checking. Final compatibility depends on the selected model's specifications and the installation conditions at your door.