Lessons 1-5 cover the base zoning code: districts (R/C/M), Use Groups, FAR, the envelope, and parking. Most NYC lots have ONE more layer on top — sometimes more.
These extra layers come in three flavors:
- Special Purpose Districts (SPDs) — neighborhood-specific overlay rules (~80 of them across NYC)
- Commercial Overlays — small commercial allowances bolted onto residential districts (C1-1, C1-2, C2-1, C2-3 mapped over R)
- Citywide Overlays — Mandatory Inclusionary Housing (MIH), Flood Resilience, Transit Zone, Waterfront, Landmarks
Each layer can MODIFY the underlying rules: change allowed Use Groups, adjust FAR, add new requirements, restrict heights, require special permits. You can't reason about a lot without knowing all the overlays that apply.
Special Purpose Districts (SPDs)
These are bespoke zoning regimes mapped to specific neighborhoods. ~80 of them total. Each one is its own mini-code (sometimes 50+ pages of rules). Examples:
| SPD | Neighborhood | What it does | |-----|--------------|--------------| | SHP (Hudson Square) | Hudson Square (Manhattan) | Encourages residential conversion of former printing buildings; allows commercial-to-residential trades; FAR bonus for affordable housing | | TMU (Theater Subdistrict) | Midtown Times Square | Requires entertainment uses; protects theaters; large-floor-plate offices need theater preservation | | MX series (Mixed Use) | Several locations | Allows residential + light manufacturing on same lot (predecessor to M-A districts post-CoY) | | HY (Hudson Yards) | Far West Side | Bonused FAR for transit improvements; specific height + setback rules for tower massing | | CR (Coney Island) | Coney | Carnival/amusement use protections; resort hotel allowances |
When you look up a parcel and see something like "Underlying: R8; Overlay: SHP" — the SHP rules MODIFY the R8 base. You read both together.
Commercial Overlays
A more limited category: small strip-commercial allowances mapped onto residential districts. Walk down a residential street in NYC and you'll see corner stores, dry cleaners, small restaurants — these exist because of a C1-1, C1-2, C2-1, or C2-3 overlay.
The overlay allows certain Use Group VI/VII uses up to a small depth (usually 100 ft) and floor area (usually 2 floors max for commercial) on top of the underlying residential rules. It's how NYC keeps mixed- use neighborhoods — even in R6+ residential districts, the corner storefront pattern is preserved.
MIH — Mandatory Inclusionary Housing
A citywide affordable-housing overlay applied selectively to neighborhoods that get rezoned for more density. ~250 MIH-mapped areas across the city. Developers in these areas creating new residential capacity must include 20-30% permanently affordable units (or pay into the AHF in limited cases).
Three options developers can pick from:
- Option 1: 25% of floor area, 60% AMI average (~$72K family of 3)
- Option 2: 30% of floor area, 80% AMI average (~$96K family of 3)
- Option 3: 20% of floor area, 40% AMI deep affordability (~$48K family of 3)
Plus a sunset "Workforce" option in some legacy maps.
Use the /zoning/learn/inclusionary-housing calculator to check any
BBL.
Flood Resilience overlay
NYC's coastal areas have FEMA SFHA (Special Flood Hazard Area) overlays — anything in 1% annual-chance flood zones triggers elevation requirements, materials restrictions, and BSA review for non-conforming improvements. After Sandy (2012), NYC also adopted Future Floodplain mapping (2020s + 2050s) used in CEQR review.
Waterfront access
If your lot touches navigable water, the Waterfront overlay rules apply: required public-access easements (visual + physical), restrictions on parking and storage at the water's edge, requirements for "Waterfront Public Access Areas" (WPAAs) for big sites.
Landmarks / Historic Districts
The LPC (Landmarks Preservation Commission) designates individual landmarks and entire historic districts. ~36,000 protected buildings across NYC.
When your lot is in a historic district, any exterior change — windows, paint color, fence, roof, storefront — requires LPC review. Demolition is essentially impossible. New construction must match "contextual" standards.
This is separate from the underlying zoning — but the two interact: an LPC restriction can block what zoning otherwise allows. A landmark designation in a R10 district doesn't reduce FAR, but it makes the FAR practically unusable on that lot.
Putting them together
Real example: a Brownstone-Brooklyn lot at 219 7th Ave (Park Slope).
- Underlying: R6B (mid-density, brownstone-scale)
- Overlay 1: C1-3 (small commercial overlay — corner-store allowed up to 100 ft depth, 2 floors commercial)
- Overlay 2: Park Slope Historic District (LPC — exterior changes require Certificate of Appropriateness)
- Overlay 3: Inner Transit Zone (zero parking required)
All four apply. To do anything meaningful here, you reconcile R6B's envelope rules, the C1-3 commercial allowance, LPC's exterior constraints, AND the parking exemption. Each one chips at what's possible.
Try the lookup
Use the widget below — enter a BBL or address, see ALL overlays that apply.