What is NYC Class S?
Class S covers primarily residential buildings that include commercial space — most commonly ground-floor retail below apartments. This is the classic NYC streetscape: a restaurant or bodega below, apartments above.
Family: Mixed-use · Approximate NYC count: ~45,000 buildings citywide
Typical characteristics
- Primarily residential (more than 50% residential)
- Ground floor or part of building used commercially
- Typically 3–6 stories
- Active commercial tenant mix
- Mixed ownership structures common (building owner leases storefronts)
Applicable laws & regulations
- HPD registration required (residential units)
- DOB compliance split: C of O must match actual use
- Commercial tenant ADA accessibility required
- FISP if 6+ stories
- LL97 if 25,000+ sqft
- Commercial waste contract (DSNY commercial franchise zones)
Common compliance issues
- C of O mismatch when commercial space changes use
- Illegal live-work or loft conversion
- Mixed-use fire separation violations
- Separate meter disputes between residential and commercial
- Sidewalk café permit non-compliance
Common zoning districts
Class S buildings are typically found in: R6A with C2-3 overlay, R7A with C1-4 overlay, C1-2, C2-3, C4, C6
Zoning determines bulk, density, and use. Checking your building's zoning alongside its class reveals what's legally possible on the lot.
Class S sub-codes
| Sub-code | Meaning |
|---|---|
| S0 | Primarily 1-family with 2 stores/offices |
| S1 | Primarily 1-family with 1 store/office |
| S2 | Primarily 2-family with 1 store/office |
| S3 | 3-family with 1 store/office |
| S4 | 4-family with 1 store/office |
| S5 | Primarily 5-6 family with stores |
| S9 | Miscellaneous single/multi-family with stores |
Frequently Asked Questions
Where do I find my NYC building class?
Your building class is set by the NYC Department of Finance and published in PLUTO (Primary Land Use Tax Lot Output) maintained by the Department of City Planning. You can look it up by searching your address on RegWatch, or directly on the DCP ZoLa portal using the lot's BBL (Borough-Block-Lot).
Can my building's class change?
Yes, but it requires a formal change. A Class S designation reflects the building's current use and configuration. Renovations that change the fundamental use (adding units, converting commercial to residential, or condo conversion) require a new Certificate of Occupancy from DOB — which may result in a new class code being assigned by DOF on the next assessment.
What compliance obligations apply specifically to Class S?
HPD registration required (residential units). DOB compliance split: C of O must match actual use. Commercial tenant ADA accessibility required. Full list above. Note that RegWatch property reports automatically calculate which obligations apply based on your building's specific characteristics (class, size, stories, construction year, occupancy).
Does a Class S designation affect resale value?
Indirectly — classification drives which regulations apply, which affects operating costs, insurance rates, and buyer expectations. Commercial classes (O, K) have different financing and diligence norms than residential (A–D). Mixed-use (S) adds complexity. Condos (R) are valued per-unit rather than per-building. Buyers and lenders always verify classification during due diligence.
How does RegWatch use building class data?
We use building class to determine which compliance obligations, deadlines, and violation patterns are relevant to each property. A Class D elevator building gets different risk flags than a Class B two-family home. This drives the per-property compliance calendar, risk scores, and vendor matching.
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