CHPC presented the following testimony during the Department of Buildings’s public hearing held on August 18, 2025, concerning its proposed rules for ADUs.
Download the testimony as a PDF.
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My name is Kate Leitch, and I am a Senior Policy Analyst at the Citizens Housing and Planning Council (CHPC), an 87-year-old policy research organization dedicated to advancing practical solutions to New York Citys housing challenges. CHPC is a member of the BASE (Basement Apartments Safe for Everyone) coalition and served as the evaluator for the East New York Basement Apartment Conversion Pilot Program.
We thank the Department of Buildings (DOB) for the opportunity to comment on the proposed addition of Section 105-08 to Subchapter E of Chapter 100 of Title 1 of the Rules of the City of New York, concerning Ancillary Dwelling Units (ADUs). These proposed rulespromulgated under Local Law 127 of 2024represent an important step toward creating a viable path to legalizing and constructing modest, lower-cost housing.
The ADU Code establishes a regulatory framework that facilitates this form of gentle density and enables owners to modify their homes to meet their needs. It achieves this by providing pathways to convert a basement or cellar into a safe, code-compliant rental unit, to create space for an adjoining above-grade unit, or to add a small, detached structure in the backyard. These changes not only address the real spatial and financial constraints of the citys lower-density neighborhoods but also resolve longstanding public safety concerns by creating a formal process to bring thousands of informal units into legal compliance. However, the realization of these benefits depends on clear regulations, consistent administration, and effective interagency coordination. CHPC emphasizes several key areas below that we strongly urge DOB to review or revise in the final rule.
1. Align Interagency Rulemaking to Ensure Clear Eligibility Standards
Although issued under separate authorities, these rules will be implemented in tandem with rules from the Department of Environmental Protection (DEP), the Department of Health and Mental Hygiene (DOHMH), and other DOB rules yet to be released. As such, coordination is crucial.
Of particular concern is an inconsistency in the definition of geographies in which basement and cellar apartments are prohibited. Whereas Local Laws 126 and 127 specifically say that the building or residence may not be in a defined area of flood risk, DEPs proposed rule says that any tax lot intersecting an area of flood risk is disqualified from eligibility. This discrepancy is not only confusing for homeowners and practitioners but may disqualify eligible buildings from participating in the program based on extraneous topographical features or lot configurations that have no bearing on the safety of the dwelling itself. There is no basis in law for rules that prohibit ADUs in locations that are not situated in an area of actual identified flood risk.
All agency rules should be harmonized around the standard adopted by the City Council in Local Laws 126 and 127focusing on whether the dwelling is located within the designated flood hazard geography, rather than whether any portion of the lot falls within it.
2. Reconsider Supplemental Requirements for Flood Sensors and Alarms
The proposed rule requires flood alarm and sensor units at potential points of water ingress, with a minimum of one and potentially up to two units per room. This exceeds the requirement of Local Law 127a minimum of one sensor per habitable roomand introduces unnecessary cost and technical complexity to the legalization process.
The additional burden is particularly pronounced for lower-income homeowners and disproportionately impacts the most modest units the program seeks to bring into compliance. Battery-operated flood alarmsanalogous to smoke or carbon monoxide detectorsare the most practical solution for flood-prone areas, especially where power loss is a risk factor during a storm event.
Battery-operated devices are widely available and typically retail for $20 or less per unit. In contrast, AC-powered units required by this rule are less common and are more expensive, often ranging from $40 to $160, and may require professional installation. We recommend that the final rule clarify that battery-powered alarms are acceptable and that a single alarm unit per roomespecially where the device has multiple sensor leadsis sufficient if placed at the lowest point of water ingress.
3. Provide Homeowners with Recourse to Address Map Errors or Changes
Ultimately, the success of the ADU program depends on its accessibility to individual homeownersmany of whom are making consequential decisions about their finances and whether to invite government scrutiny of their homes. The rules should provide recourse to address errors or ambiguities in determinations of geographic eligibility.
As is known from the experience of administering existing flood hazard maps at DOB, there is sometimes a need to address errors in maps or changes in physical conditions (e.g., regrading of land). RCNY 3606-02 lays out the process by which DOB administers a map change approved by FEMA, but no similar process is presented in the proposed rules to administer the inland flood maps generated by DEP. While addressing such issues can present administrative challenges for a homeowner, the absence of any recourse whatsoever is a more egregious problem. This issue is exacerbated by the division of responsibility for these maps between two City agencies. We urge DOB, in close coordination with DEP, to amend rules to establish a formal mechanism for homeowners to seek clarification or pursue an amendment based on site-specific data, analogous to FEMAs Letter of Map Amendment (LOMA) process.
4. Avoid Incorporating Inapplicable or Duplicative Code-Like Provisions
Subsection (4) of the Eligibility section introduces building code-like requirements that govern the construction of new single-family homes containing a cellar ADU. However, the Housing Maintenance Code does not permit a cellar to serve as a legal residence. It is unclear what regulatory gap these provisions are attempting to fill.
We recommend removing or clarifying this section to prevent confusion. Incorporating code-like requirements into the rule instead of or alongside the actual code risks creating discrepanciesparticularly with future code updatesand complicates plan reviews.
The rules authorized under the new ADU Code offer an opportunity to expand safe, lower-cost housing options in lower-density neighborhoods and to bring long-existing informal housing under government oversight. But the opportunity can only be realized if the program is built on clear standards, consistent administration, and a recognition of the constrained technical capacity of applicants.
We thank the Department for its significant efforts to launch this critical program and welcome the opportunity to continue supporting its successful implementation.