DOB Proposed Rules: Basement and Cellar ADU Entrance Signs and Natural Gas Alarms

Last updated: October 26, 2026 · By S & M Expediting

DOB has proposed two rules that are open for public comment: one requires a red-on-white entrance sign for some basement and cellar apartments (ADUs), with a hearing and comment deadline on November 4, 2026, and one clarifies where natural gas alarms go, with a hearing and comment deadline on November 16, 2026. Both are proposed, not final.

## What would DOB's proposed ADU entrance sign rule require? If a basement or cellar ancillary dwelling unit's entrance isn't apparent from the street and there is no existing identification sign, DOB proposes a permanent sign mounted on or near the main house, placed where it can be plainly seen from the street or fire apparatus access road. The proposed sign must have: - Red letters on a white background - Letters and numbers at least 4 inches tall, with a stroke at least ½ inch wide - A sign at least 11 inches tall by 17 inches wide - Row one: "ADU-BAS" for a basement unit or "ADU-CEL" for a cellar unit - Row two: "EXP - 1", "EXP - 2", "EXP - 3" or "EXP - 4", naming the side of the building where the entrance is

### How are the building sides (exposures) numbered? Exposure 1 is the side facing the street of the building's official address. Exposure 2 is to the left when you stand in the street facing Exposure 1, Exposure 3 is the opposite side, and Exposure 4 is to the right.

### Do I have to replace a sign I already have? Under the proposal, no, if your existing identification sign was in place when the new rule takes effect and it complies with the rule in force before then. The current rule calls for a directional sentence-form sign; the proposal replaces that with the short code format above.

### Why does DOB want these signs? DOB says the change came out of required consultations with the Fire Department and the Office of Emergency Management, and clarifies entrance identification so firefighters can find the unit in an emergency. The authority comes from Local Law 127 of 2024 and Appendix U of the NYC Building Code. Source: DOB's proposed ADU rule.

## What would the proposed natural gas alarm rule change? DOB proposes to clarify where natural gas alarms must be installed in residential buildings. The proposal would: - Exempt buildings with no gas service. - Exempt Class A and Class B dwelling units with no gas appliance, as long as the space directly below the unit has no gas appliance or gas piping. If the space below does have gas, the unit still needs an alarm. - Require a vented shaft and a gas detector at or near the top where gas piping in a shaft serves only emergency, standby or optional generators. - Limit the adopted NFPA 715 standard to private dwellings and Class A and Class B multiple dwellings. - Allow a monitored battery primary power source in existing buildings completed before January 1, 2027.

Source: DOB's proposed natural gas alarm rule.

## When do NYC buildings have to install natural gas alarms? On or before January 1, 2027. Local Law 102 of 2025 moved the deadline from May 1, 2025, and the proposed rule updates DOB's rules to match. The hearing is about the details, not the deadline, so plan installations now. Our NYC year-end compliance deadlines page lists this alongside other dates.

## How do I comment on or speak at a DOB rule hearing? - Comment online: use the comment form on each rule's page at rules.cityofnewyork.us. - Email: dobrules@buildings.nyc.gov. - Speak at the hearing: email dobrules@buildings.nyc.gov with your name and affiliation by the sign-up date (Nov 9 for gas alarms; the ADU sign-up closed Oct 28). Speakers get up to three minutes. The hearings take testimony only; they aren't question-and-answer sessions. - Join online: both hearings are held online. The links and dial-in details are on each rule's page.

## Are these rules in effect now? No. Both are proposed. DOB can change them after the comment period, and they only take effect once a final rule is adopted and published. The January 1, 2027 gas alarm deadline is set by law, though, and already applies.

## Can S & M Expediting help with a basement or cellar unit? Yes. If you're adding or legalizing a basement or cellar unit, we handle the DOB filings. Start with our guide to ancillary dwelling units (ADUs) in NYC. We will work with the contractor you have, or if not, we will recommend one from our network.

Call 718-833-2333 or email info@sandmexpediting.com

This article summarizes proposed DOB rules for general information. It is not legal advice. The final rules may differ.