Smart Locks for ADUs and Granny Flats in San Diego

San Diego has permitted a lot of accessory dwelling units in recent years, and every one of them raises the same question at the door: who has the key? A granny flat for a parent, a garage conversion rented on a year lease, a junior ADU carved out of a spare bedroom. Each needs a lock that separates the unit from the house without locking the owner out. Here is how we set them up.

Why does an ADU need its own key?

Three reasons. Privacy: a tenant is entitled to a door that only they and the owner can open, and they should never be carrying a key to your house. Turnover: when a tenant leaves, you need to shut off their access without touching the locks on your own home. Family: even a relative in a granny flat usually wants a door that the grandchildren cannot wander through.

The reverse matters too. If your house key opens the ADU, so does the copy you gave the dog walker. Keep the two systems apart, and keep the paper trail described in our landlord rekeying guide.

The three kinds of ADU and their door problems

Detached new build

A backyard unit built from plans comes with a standard prehung exterior door, a 2-1/8 inch bore and usually a builder Kwikset deadbolt. Any keypad or smart lock fits without drilling. The only real question is Wi-Fi reach, covered below.

Garage conversion

Two situations. Either the old side door from the garage to the yard becomes the entry, or a new entry door goes in where the roll-up door used to be. The old side door is often thin, sometimes hollow, with a knob lock and a strike held by short screws. Fix the door before you spend on a lock. The permit set usually says what happens to the old door into the house; where one remains, it needs a lock that keeps both sides private.

Junior ADU

A junior ADU sits inside the walls of the house with its own entrance and, often, a door connecting to the main home. That connecting door is the weak point: a hollow-core interior slab with a passage knob. It needs a solid-core door, a proper strike and a deadbolt that locks from the unit side. The exterior entrance gets its own keypad.

Why a keypad makes turnover a code change

With a keyed lock, every tenant change is a rekey. With a keypad deadbolt, it is a two-minute code change: delete the old code, add a new one, done. The keyway stays and the tenant still gets a physical key, which most leases expect and which covers the day the batteries die. You only rekey the override if a key went missing.

That routine is what our landlord turnover service is built around, and owners with more than one unit get the same treatment on our property manager page.

Wi-Fi reach in a detached unit

A detached ADU in a Clairemont or La Mesa backyard is often 40 to 80 feet from the house router, through stucco and a garage. Built-in Wi-Fi locks struggle at that distance. Three fixes:

1. A mesh node or extender inside the ADU on the owner’s network, if the owner manages the lock.
2. A Bluetooth lock with a bridge. August, Level and Ultraloq all offer a bridge; put it in the main house on the wall nearest the unit.
3. Skip the radio. A keypad-only lock needs no network. Codes are changed at the door.

Decide whose network the lock lives on before you buy. If the tenant brings their own internet, the owner’s remote access depends on the owner’s network reaching the door.

Shared gates and side yards

Most ADUs are reached through a side yard gate that the main house also uses. Give it a keyed latch or a keypad gate lock so the tenant does not need to cross through the house, and keep that key separate from the house key. Our sliding door and gate lock service fits both.

Long-term or short-term rental?

For a long-term rental, California Civil Code 1941.3 requires the landlord to provide a deadbolt on the main entry door and working window locks. A keypad deadbolt with a standard full-throw bolt satisfies the deadbolt part; giving the tenant a physical key as well is standard practice.

Short-term use is mostly off the table. State ADU law lets cities require that an ADU be rented for 30 days or longer, and requires it for junior ADUs. The City of San Diego’s ADU rules do not allow leases shorter than 31 consecutive days, and its Short-Term Residential Occupancy ordinance excludes ADUs, with an exception only for companion units permitted before the City’s 2017 prohibition. This is general information, not legal advice; check current rules before you list. If your unit does qualify, the scheduled-code setup in our Airbnb smart lock guide applies to an ADU just as well.

Owner access without holding the tenant’s key

On a keypad or smart lock, the owner keeps an admin code and the tenant has their own. Entry still follows notice rules, but you are never locked out of your own property.

On keyed locks, the answer is master keying. Your key opens the house and the ADU; the tenant’s key opens only the ADU. This works on conventional pin tumbler cylinders, which includes Schlage and standard Kwikset, and it is set up as part of a keyed-alike visit. It does not work on Kwikset SmartKey cylinders, so a SmartKey lock on the ADU door gets swapped for one that can join the system.

Which locks fit an ADU?

• Wi-Fi keypad deadbolts. Schlage Encode has Wi-Fi built in and a rekeyable Schlage keyway. Yale Assure Lock 2 with the Wi-Fi module is the other standard pick, keyed or key-free.
• Fingerprint. The Ultraloq U-Bolt Pro adds a fingerprint reader to a keypad and key override, which tenants like and owners find easy to manage.
• No app at all. A plain keypad deadbolt from Schlage or Kwikset. Codes at the door, no account, no Wi-Fi.
• Keep the existing hardware. When the ADU door already has matching hardware you want to keep, an August Wi-Fi Smart Lock or a Level Bolt adds smart control without changing the outside.

Garage conversions and junior ADUs are common across older tracts in City Heights, Encanto, Linda Vista and Lemon Grove, and backyard units are going up behind homes in North Park and El Cajon. The door work is different in each case, so send a photo of the entry before choosing the lock. Our picks by use case are in best smart locks for San Diego homes.

Next step

Book a smart lock installation for the ADU door and tell us whether the unit is detached, a garage conversion or a junior ADU. We check the door, fit the lock, set the owner and tenant codes, sort out the gate, and key the override so your key opens everything and the tenant’s opens only theirs.