The legalization of basement apartments is a policy issue that lives at the intersection of housing, climate change, and social justice. New York’s expensive and highly constrained housing market drives many low-income families with little housing choice into informal rental apartments that exist outside of city oversight. As a result, some New Yorkers end up living in substandard or even hazardous conditions. Hurricane Ida cruelly exposed the dangers of living in apartments that haven’t been vetted for safety.

Rather than make the regulatory framework that is partly responsible for discouraging the legalization of basement units more restrictive, the city should streamline a path to compliance, incentivize installation of essential safety features, and help residential properties with projected flood risk meet a higher standard of storm safety.

In addition to realigning regulatory requirements to prioritize safety, the city must implement policies to manage stormwater runoff more actively and equitably. Currently, the cost of stormwater flooding—polluted waterbodies, unsanitary living conditions, property loss, displacement, and death—is borne by a small number of New Yorkers, though stormwater runoff is generated by nearly all properties.

As climate change accelerates our vulnerability to sea-level rise and makes extreme rain events more common, there are actions that individuals, communities, and the city can embrace to both unburden the city’s storm infrastructure and protect lives.

This report explores possible interventions designed for city-, neighborhood-, and lot-level accountability.

On September 1, 2021, historically heavy rain from Hurricane Ida swept through New York City, exceeding the capacity of the city’s sewers and claiming the lives of 13 New Yorkers, 11 of whom were living in unregulated basement apartments. The extreme rain event overwhelmed New York City’s antiquated combined sewer system and created a flood event that was previously unimaginable. In fact, many more residential properties are impacted by stormwater flooding than coastal flooding, according to projected stormwater maps published by the city.


  • Create a practical pathway to legalization of basement apartments.
  • Employ emergency push-alerts.
  • Require flash flood safety plans.
  • Impose a stormwater fee.


  • Incentivize removal of paved areas of replacement with permeable alternatives.
  • Revive and expand rain barrel giveaway programs.
  • Prioritize targeted stormwater infrastructure.


  • Ensure access to reliable, unobstructed, code-compliant egress routes.
  • Install backwater valves in basements.
  • Utilize flood sensors and alarms.
  • Emphasize effective bulk water control.