We ran RunEnvelope’s zoning engine over 89,362 tax lots in the Bronx. 2,164 privately owned sites have at least 20,000 square feet of as-of-right room for housing and are built to half of it or less.
square feet across 2,164 sites. 125.3M of it needs no affordability program.
The unit count of the largest apartment scheme on each site, minus the 17,204 homes there today. A ceiling, not a forecast.
of the room for housing on the 3,978 lots analyzed sits on 1,833 lots built to less than a quarter of their largest housing scheme, or not built at all.
Commercial and office holds the most room for housing in the Bronx: 68.4M square feet on 1,219 lots, 39% of the total.
City Planning land use codes as recorded in PLUTO.
Built floor area as a share of the lot’s largest housing scheme.
| Built to | Lots | Room for housing |
|---|---|---|
| Nothing built | 400 | 23.2M sf |
| Under 25% | 1,433 | 83.4M sf |
| 25 to 50% | 637 | 37.7M sf |
| 50 to 75% | 549 | 25.8M sf |
| 75 to 100% | 88 | 1.7M sf |
| At or above 100% | 13 | 0M sf |
Bronx Community District 4 leads with 30M square feet of room for housing and 310 sites.
| Community district | Lots | Room for housing | Sites |
|---|---|---|---|
| Bronx Community District 4 | 511 | 30M sf | 310 |
| Bronx Community District 10 | 265 | 21.7M sf | 164 |
| Bronx Community District 5 | 446 | 19.4M sf | 282 |
| Bronx Community District 7 | 406 | 17.4M sf | 227 |
| Bronx Community District 9 | 256 | 14M sf | 130 |
| Bronx Community District 11 | 265 | 13.7M sf | 163 |
| Bronx Community District 1 | 353 | 13.4M sf | 148 |
| Bronx Community District 8 | 325 | 11.5M sf | 209 |
| Bronx Community District 3 | 238 | 9.5M sf | 142 |
| Bronx Community District 6 | 230 | 9.2M sf | 176 |
| District family | Room | Sites |
|---|---|---|
| Residential (R) | 120.9M sf | 1,698 |
| Commercial (C) | 42.2M sf | 379 |
| Mixed manufacturing and residential (MX) | 8.7M sf | 87 |
| Manufacturing (M) | 0M sf | 0 |
Counted by the lot’s zoning district. Manufacturing districts mostly do not allow housing, so their room is small by definition. District reference.
The quick way to underwrite a lot is to multiply its area by the residential FAR in PLUTO. On the 3,103 analyzed lots where both allow housing, that gives 180.6M square feet. The engine’s largest residential-only building, with no affordability program, comes to 195.8M: 8% more in total. The total hides the lot-by-lot picture: the engine lands within 10% of the simple number on 1,600 lots, more than 10% above it on 1,455, and more than 10% below it on 48.
More can come from rules PLUTO’s single figure does not capture, such as the higher FAR on a wide street or a commercial district’s residential equivalent. Less can come from a lot too small or narrow for the height and setback rules to fit the full FAR. Each example below links to the lot’s page with its scenarios.
| Lot | PLUTO FAR x area | Engine |
|---|---|---|
| 2426 Eastchester Road R4A · 41,300 sf lot · wide street | 41,300 sf FAR 1 | 61,950 sf Max Apartments |
| 1800 Williamsbridge Road R4A · 35,000 sf lot · wide street | 35,000 sf FAR 1 | 52,500 sf Max Apartments |
| 1430 Unionport Road R6 · 14,936 sf lot · wide street | 36,294 sf FAR 2.43 | 44,808 sf Max Apartments |
Examples are drawn from our published The Bronx lot pages, which pass extra data quality checks, and ranked by the ratio of the two numbers. Each is a single screening result: open the lot page for its scenarios, and treat it as a reason to look closer, not a conclusion.
Our soft sites study counted 1,356 sites in the Bronx from PLUTO alone. The engine assessed 1,153 of them (the rest are public, missing a built area, or failed a check). PLUTO puts their unused residential floor area at 66.8M square feet. The engine finds 72M for residential-only buildings, 89.6M once mixed-use schemes with homes count, and 98.4M with the affordable and senior housing schemes.
RunEnvelope precomputes its zoning analysis for every tax lot in PLUTO 26v2: the same engine as a report, run in screening mode from the City’s recorded lot dimensions rather than a surveyed outline. For each lot we use:
| Engine could not compute (error, or no zoning district) | 805 |
|---|---|
| Public, institutional or open space | 6,705 |
| Condominium or co-op | 701 |
| Buildings present but no built floor area recorded | 946 |
| Largest scheme above the district's maximum FAR | 142 |
| Less unused floor area than the floor | 76,085 |
| Analyzed: one and two family homes | 353 |
| Analyzed: all other private lots | 3,625 |
| Tax lots in the Bronx | 89,362 |
Each lot is counted once, in the first class that applies, top to bottom. Public and institutional land, condominiums and co-ops follow the same rules as the soft sites study.
It counts what the zoning permits, not what will be built. Landmarked buildings and lots in historic districts are included in these totals (the lot pages leave them out). It cannot see who lives or works on a lot, leases, ground conditions, financing or whether anyone wants to sell. PLUTO’s built floor area comes from tax records and is least reliable on large, irregular lots. Treat any single lot as a lead worth checking.
Computed October 25, 2026 against PLUTO 26v2 by scripts_seo/borough_research.py. Reuse with attribution and a link to this page.