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Smart locks for double cylinder deadbolts and storm doors
Updated
A double cylinder deadbolt has a keyhole on both sides. Retrofit smart locks cannot go on it: August's support page lists double cylinder deadbolts as not compatible. Your option is to replace the whole deadbolt with a smart deadbolt, which has a thumb turn on the inside. With a storm door, the question is room: the outside keypad has to fit between the two doors.
Double cylinder: what changes
The smart deadbolts on our list are single cylinder: a keypad or key outside and a turn inside, not a keyhole. So going smart means going from a key inside to a turn inside. People often chose a double cylinder because there is glass near the lock. Think about that before you swap.
The flip side is safety. A key inside can slow you down when you need to get out fast, like in a fire. Rules on keyed inside locks differ by place. Ask your local building or fire department if you are unsure. This page is general information, not security or legal advice.
- Schlage Encode: a full replacement for a standard door, 1-3/8 to 1-3/4 inches thick. Caveat: owners are split on battery life.
- eufy C220: listing says no drilling, and fingerprint entry. Caveat: Grade 3, the basic residential grade.
Storm doors: the gap
A keypad or fingerprint lock has an outside part that sticks out from the door. If a storm door closes in front of it, the storm door can hit it or stop short. Do this before you buy:
- Close the storm door. Measure the gap between the face of your main door and the back of the storm door, at the height of the deadbolt.
- Look for the outside depth of the lock in the manual or spec sheet. We did not find a clear outside depth on the listings we read, so ask the maker if it is missing.
- Check the storm door's own handle. It must not line up with the new lock.
There is also a daily use issue. You will have to open the storm door to reach the keypad or the fingerprint reader every time.
The storm door workaround
A retrofit lock goes on the inside only. The August Wi-Fi Smart Lock leaves the outside of the door as it is, so the storm door gap does not change. It still needs a single cylinder deadbolt. Caveat: no keypad unless you buy one, and owners report short battery life.
Other clearance checks
- Yale's listing asks for at least 4 inches center to center between the deadbolt and the handle below.
- eufy's listing asks for more than 45 mm from the lock hole center to the top of the handleset.
- Raised trim or glass next to the inside of the lock can block the bigger inside unit.
Run your numbers through the fit checker. Yale's support page also walks through door types it cannot fit, like mortise prepped doors.