Yes, attic ADUs are allowed in New York City as of October 2026, as long as they meet the Building Code's Appendix U. DOB says attic ADUs must always be sprinklered, and HPD's guidebook says the attic must generally provide at least 7 feet of clear ceiling height over a required portion of the floor.
Which homes can have an attic ADU?
DOB's September 2025 announcement described attic apartments in one-family homes. In a two-family house, adding a third unit can bring Multiple Dwelling Law requirements, which raise the bar on fire safety and exits. We check your building class and certificate of occupancy before designing.
How is an attic ADU filed?
When the ADU is inside the same building, DOB says it is filed in DOB NOW as an Alteration CO job. The new certificate of occupancy lists the ADU. See the permit guide.
What makes an attic workable?
- Headroom over enough of the floor, which can mean dormers or a reframed roof.
- A code stair that does not eat the floor below.
- Exits that meet Appendix U, and windows that serve as emergency openings where needed.
- A sprinkler system, which DOB requires in every attic ADU.
- Insulation and cooling at the roof line, because attics run hot in a New York summer.
Do flood rules affect an attic unit?
Less than they affect a basement. DOB's rule allows above-grade ADUs in flood areas in buildings that lawfully existed on or before December 5, 2024, subject to elevation requirements. We review how those apply to your house.