Greenburgh staff advise limited expansion of ADU eligibility to 7,500-sq-ft lots with safeguards

Planning staff updated the Town Board on proposed changes to the accessory dwelling unit local law at the Feb. 10 work session, including analysis of how a lower lot-size threshold would change the pool of eligible conversions.

Garrett, the planner presenting the analysis, said Greenburgh has roughly 9,000 single-family homes; after filtering for detached accessory garages larger than 400 square feet there are about 325 such garages. Under the local law draft posted in December, 242 of those garages were on lots of at least 10,000 square feet. Lowering the minimum lot size to 7,500 square feet would add about 20 garages to the eligible pool, bringing the total to roughly 262.

Staff proposed language that would allow conversions of lawfully existing accessory structures to ADUs provided there is no expansion of the accessory structure and that off-street parking, driveway setback and impervious-cover rules conform to protections similar to an R-7.5 bulk standard in certain districts. Garrett said the draft retains a 20,000-square-foot minimum for detached ADUs required to be in a backyard and would keep a 10,000-square-foot minimum for ADUs created by expanding the principal house.

Board members raised concerns about conversions where garages or driveways sit at or near a property line (noise, lack of mitigation space) and asked staff to report back on how many of the newly eligible garages actually abut property lines. Planning staff said they would produce that additional data and suggested the changes could be posted for the Feb. 25 public hearing with a one-year sunset so the board can revisit outcomes.

No local-law adoption vote occurred on Feb. 10; staff recommended additional analysis and outreach before a final decision.