51 S Market St
51 S Market St is a 8-story building in Downtown San Jose with 67% of its floor area within daylight reach of a facade. This screen estimates 146 homes and scores it 52 out of 100 for office-to-residential conversion suitability.
CA-18 · Screened 2026-09-12 · Worth a feasibility study
Also addressed as 55 S Market St: San Jose’s address records place both on this one footprint.
Where 51 S Market St is
Its block in Downtown San Jose, drawn from San Jose's own building outlines and street centerlines.
- Already housing
- Not screened
- 51 S Market St
This building does not pencil at default assumptions, even with a modeled RESIDE Act grant.
Every floor carries 9,775 sq ft of windowless core — area that must be gutted, seismically braced and sprinklered but can never be rented as an apartment. Across 7 residential floors that is 68,423 sq ft of cost carrying no revenue.
Modeled conversion metrics for 51 S Market St, 2026-09-12.
| Suitability scoreWorth a feasibility study | 52 / 100 |
|---|---|
| Storiesfrom 91 ft LiDAR height ÷ 12 ft floor-to-floor | 8 |
| Floor plateper floor, from the city footprint | 29,372 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 67% |
| Deepest interior pointviability threshold is 80 ft | 76 ft |
| Windowless coreper floor — renovated but never rentable | 9,775 sq ft |
| Estimated homesat 750 sq ft average | 146 |
| Conversion cost$405/sq ft all-in on 205,601 sq ft | $83.3M |
| Gap before grantshortfall against completed value | $21.2M |
| Modeled RESIDE grantbelow the statutory cap | $8.8M |
| BuiltSan Jose does not publish a construction year with this data | — |
| ZoningDowntown San Jose | DC |
| Opportunity Zonecensus tract 06085500800, 2018 designation | Yes |
The plan: window line, shape and floor rhythm
36 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.
The typical floor has 747 ft of exterior wall, and across 7 residential floors the building carries 5,228 ft of it in total, divided among the 146 homes this screen estimates.
Its plate is moderately compact at 0.66: a squarish plan, with enough perimeter for a conventional double-loaded corridor. How window line and plate shape are measured.
At the model’s 750 sq ft average, the plan works out at about 20.9 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 51 S Market St scores 52 out of 100
Daylight efficiency 53, Interior depth 9, Scale 97, Finance 75 — each out of 100, then weighted.
Score components for 51 S Market St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency67% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 53 | 45% | 24.0 |
| Interior depthdeepest interior point 76 ft from a facade, scored from 80 ft down to 40 ft | 9 | 25% | 2.4 |
| Scale146 estimated homes, scored from 0 up to 150 | 97 | 15% | 14.6 |
| Financeremaining gap is 15% of conversion cost, scored from 60% down to 0% | 75 | 15% | 11.3 |
Most of what it earns comes from daylight efficiency, and what holds it back most is interior depth, at 9 out of 100: deepest interior point 76 ft from a facade, scored from 80 ft down to 40 ft.
What the conversion would cost
$405 per square foot all-in across 205,601 sq ft of converted floor, or $83.3M in total — about $570K for each of the 146 homes.
All-in cost per square foot for 51 S Market St: base cost plus the code work a change of use triggers.
| Base conversion cost | $260/sq ft |
|---|---|
| Seismic retrofit (change of use) | $45/sq ft |
| Plumbing risers to every unit | $40/sq ft |
| Operable windows and glazing | $30/sq ft |
| Additional egress stair | $18/sq ft |
| Fire sprinklers (NFPA 13R) | $12/sq ft |
| All-in | $405/sq ft |
That cost is charged across every converted square foot, including the 68,423 sq ft of windowless core, which has to be gutted, seismically braced and sprinklered like the rest of the building and then earns nothing. Against it the model sets a completed value of $425K a home, which for 146 homes is $62.0M.
What would have to be true
A $21.2M gap before any grant, $12.5M after the modeled one. The smallest single change that would close it: average unit size 15% down.
The shortfall before any grant is $21.2M. Closing it from the value side means each of the 146 homes finishing at $570K rather than the $425K the model assumes — 34% more. Closing it from the cost side means getting all-in cost down from $405 to $302 per square foot.
A modeled RESIDE grant of $8.8M moves that threshold to $510K a home. That is still above the $425K assumed, leaving $12.5M uncovered, which is why the grant does not unlock this one.
Nor do all four levers have to move. For 51 S Market St, one alone would close the gap at:
Single-assumption flip points for 51 S Market St, each holding the other three at their defaults.
| Average unit sizethe binding constraint — the least this building would need | 15% downto 634 sq ft |
|---|---|
| Circulation efficiency | 18% upto 95% |
| Completed value per home | 20% upto $510K |
| Conversion cost per square foot | 23% downto $199/sq ft |
All four are sliders in the survey, where 51 S Market St re-scores against your own numbers.
How it compares in Downtown San Jose
51 S Market St ranks 52nd of the 82 buildings screened here, against a median score of 64.
Its floor plate is better lit than 40% of them, and shallower than 35% of them at its deepest interior point. On size it is the 57th largest by estimated homes. The full survey of all 82 buildings ranks and maps every one of them, and the list by address links each to its own page.
Within the DC zone
43rd of 72 zoned DC — the comparison that shares its rules, rents and streets.
72 of the screened buildings are zoned DC. 51 S Market St ranks 43rd of them against a median score of 61. 31 score 70 or more, their median deepest interior point is 68 ft from a facade against this building’s 76 ft, and together they would hold an estimated 23,276 homes. The group’s top scorer is 1 Almaden Blvd, at 100.
Its nearest match in size: 505 E Santa Clara St
The screened building closest to 51 S Market St in converted floor area is 505 E Santa Clara St: 203,775 sq ft over 8 stories, against 205,601 sq ft over 8 here.
51 S Market St scores 52 to its 89, and with the size held roughly equal most of that shortfall comes from daylight efficiency: 53 out of 100 here, 97 there (89% of the floor area within 35 ft of a facade, scored from 40% up to 90%). On the money they part ways: 505 E Santa Clara St pencils only with the modeled RESIDE grant, while 51 S Market St falls short even with the modeled grant. The two stand about 4,400 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 51 S Market St $8.8M, on the assumption it qualifies. Whether it does, no published dataset can say.
That figure assumes the building meets the Act’s vacant-and-abandoned test, which turns on code-enforcement and receivership records no city publishes.
This building does sit in census tract 06085500800, a 2018 designated Opportunity Zone, which Section 201 lets HUD favor — one of the few statutory priorities this screen can actually check.
Other buildings screened near 51 S Market St
The 4 closest the screen also covers, from 170 ft away. They are the colored outlines on the plan at the top of this page.
- 95 S Market St8 stories · 59% daylit · 163 estimated homes · scores 35/100 (Marginal)about 170 ft away
- 60 S Market St18 stories · 79% daylit · 241 estimated homes · scores 78/100 (Strong candidate)about 260 ft away
- 127 Post St20 stories · 62% daylit · 687 estimated homes · scores 35/100 (Marginal)about 280 ft away
- 81 Post St9 stories · 100% daylit · 51 estimated homes · scores 90/100 (Strong candidate)about 300 ft away
A screen, not a feasibility study, from outlines and heights rather than plans: the method and how to correct a figure. If you know this building’s interior, you know what this model cannot see.