Can an ADU's front door have a deadbolt? What CBC 1010.2.4 says

Every ADU builder, homeowner, and residential designer eventually asks the same question at the hardware store: can the front door have a deadbolt? The egress code seems to say no. Read it again, and the answer is yes — with one line you cannot cross.

Here's where the confusion starts. The general unlatching rule, CBC Section 1010.2.1, is blunt. A door in the means of egress has to release all its latching and locking devices in "not more than one motion in a single linear or rotational direction" — and then it adds, flatly, "Manual bolts are not permitted." A deadbolt throws a bolt by hand. A night latch adds a second motion. Taken alone, that sentence reads like a ban on the most ordinary lock on an American front door.

The carve-out lives in Item 5

It doesn't ban it, because a few subsections later the code carves out dwellings. Section 1010.2.4 lists the conditions under which "locks and latches shall be permitted to prevent operation of doors," and Item 5 is the one that matters for a home or ADU.

Verified against CBC §1010.2.4, Item 5 (2025 edition, effective January 1, 2026): "Single exit doors ... from individual dwelling or sleeping units of Group R occupancies and equipped with a night latch, dead bolt, manual bolt, or security chain that requires a second releasing motion, provided that such devices are openable from the inside without the use of a key or tool."

The permitted hardware is spelled out by name — night latch, dead bolt, manual bolt, or security chain — and the second releasing motion is expressly allowed, even though 1010.2.1 otherwise demands a single motion. The two sections aren't in conflict. Section 1010.2.1's own Exception 3 points straight at "Doors from individual dwelling units and sleeping units of Group R occupancies as permitted by Section 1010.2.4, Item 5."

The line you can't cross

Read Item 5's last clause again, because it's the whole game: the device must be "openable from the inside without the use of a key or tool."

That single phrase decides the hardware aisle.

• A single-cylinder deadbolt with a thumb-turn on the inside? Passes. You leave by twisting the turn — no key, no tool.
• A double-cylinder deadbolt — keyed on both sides, the kind people install beside a glass-panel door so nobody can break the glass and turn the lock — fails. You can't get out without a key, and that is exactly what Item 5 forbids.

It's the same principle the general rule states in 1010.2: an egress door has to be "readily openable from the egress side without the use of a key or special knowledge or effort." Security on the outside is fine. Anything that traps a person on the inside is not.

What the January 2026 errata actually did

If you've heard there was a "change" to this section, here's the honest version: the January 2026 Title 24 errata cleaned up the wording of Item 5 — it didn't rewrite the rule. The errata, announced in BSC Information Bulletin 26-01 and effective January 1, 2026, are catalogued as non-substantive corrections. The dwelling-unit carve-out for a deadbolt or night latch isn't new — it predates this errata. The correction simply made Item 5 read cleanly: these devices are allowed on a dwelling's single exit door, provided they're openable from the inside without a key or tool.

So nobody's hardware spec became illegal overnight, and nothing new became legal. What changed is that the line is easier to read on the page.

What this means Monday morning

For a single-family home or an ADU whose entry is a single exit door, the bright line is simple:

• Deadbolts and night latches are fine — as long as you can open them from the inside with a turn of the hand.
• A thumb-turn is your friend. It's the difference between a compliant lock and a correction.
• Double-cylinder, key-both-sides locks are the trap. They're the one residential security upgrade most likely to draw a plan-check comment or fail at final.

One caution: occupancy classification and local amendments vary, and a detached ADU may be reviewed under the Residential Code rather than the Building Code. The "no key or tool to get out" principle runs through both, but verify with your local jurisdiction before you finalize hardware — your building official has the last word on which book and which corrections they enforce. This isn't legal advice.

What CrossBeam does with it

CrossBeam checks egress-door hardware against the carve-out that actually governs it, so a double-cylinder deadbolt on a home's only exit door gets flagged before it reaches a counter. It's the kind of detail that's easy to spec for security and easy to miss for egress.