121 S Market St
121 S Market St is a 9-story building in Downtown San Jose with 89% of its floor area within daylight reach of a facade. This screen estimates 84 homes and scores it 84 out of 100 for office-to-residential conversion suitability.
CA-18 · Screened 2026-10-20 · Strong candidate
Where 121 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
- 121 S Market St
This building does not pencil on its own, but a modeled RESIDE Act grant would close the gap if the building qualified for one.
Every floor carries 1,261 sq ft of windowless core — area that must be gutted, seismically braced and sprinklered but can never be rented as an apartment. Across 8 residential floors that is 10,084 sq ft of cost carrying no revenue.
Modeled conversion metrics for 121 S Market St, 2026-10-20.
| Suitability scoreStrong candidate | 84 / 100 |
|---|---|
| Storiesfrom OpenStreetMap, “Wells Fargo, way 158248750”, in place of the 142 ft LiDAR height ÷ 12 ft floor-to-floor | 9 |
| Floor plateper floor, from the city footprint | 11,131 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 89% |
| Deepest interior pointviability threshold is 80 ft | 52 ft |
| Windowless coreper floor — renovated but never rentable | 1,261 sq ft |
| Estimated homesat 750 sq ft average | 84 |
| Conversion cost$405/sq ft all-in on 89,050 sq ft | $36.1M |
| Gap before grantshortfall against completed value | $365K |
| Modeled RESIDE grantbelow the statutory cap | $5.0M |
| 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
40 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.
The typical floor has 422 ft of exterior wall, and across 8 residential floors the building carries 3,376 ft of it in total, divided among the 84 homes this screen estimates.
Its plate is compact at 0.79: close to a square or a circle, the most efficient envelope an office can have and the least generous one for apartments: little perimeter to divide among homes. How window line and plate shape are measured.
At the model’s 750 sq ft average, the plan works out at about 10.5 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 121 S Market St scores 84 out of 100
Daylight efficiency 97, Interior depth 69, Scale 56, Finance 100 — each out of 100, then weighted.
Score components for 121 S Market St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency89% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 97 | 45% | 43.8 |
| Interior depthdeepest interior point 52 ft from a facade, scored from 80 ft down to 40 ft | 69 | 25% | 17.2 |
| Scale84 estimated homes, scored from 0 up to 150 | 56 | 15% | 8.4 |
| Financecompleted value covers conversion cost with 13% to spare, which tops out the component | 100 | 15% | 15.0 |
Most of what it earns comes from daylight efficiency, and what holds it back most is scale, at 56 out of 100: 84 estimated homes, scored from 0 up to 150.
What the conversion would cost
$405 per square foot all-in across 89,050 sq ft of converted floor, or $36.1M in total — about $429K for each of the 84 homes.
All-in cost per square foot for 121 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 10,084 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 84 homes is $35.7M.
What would have to be true
A $365K gap before any grant, which the modeled $5.0M closes. What would reopen it soonest: circulation efficiency 11% down.
The shortfall before any grant is $365K. Closing it from the value side means each of the 84 homes finishing at $429K rather than the $425K the model assumes — 1% more. Closing it from the cost side means getting all-in cost down from $405 to $401 per square foot.
A modeled RESIDE grant of $5.0M moves that threshold to $369K a home. That is below the assumed value, which is why this building counts as penciling with the grant, at market rents — subject to it qualifying under the law's vacant-and-abandoned test, which this data cannot show.
Each of these, moved on its own, would be enough to undo that for 121 S Market St:
Single-assumption flip points for 121 S Market St, each holding the other three at their defaults.
| Circulation efficiencythe binding constraint — the least this building would need | 11% downto 71% |
|---|---|
| Average unit size | 12% upto 842 sq ft |
| Completed value per home | 13% downto $369K |
| Conversion cost per square foot | 20% upto $312/sq ft |
All four are sliders in the survey, where 121 S Market St re-scores against your own numbers.
How it compares in Downtown San Jose
121 S Market St ranks 15th of the 47 buildings screened here, against a median score of 77.
Its floor plate is better lit than 74% of them, and shallower than 70% of them at its deepest interior point. On size it is the 38th largest by estimated homes. The full survey of all 47 buildings ranks and maps every one of them, and the list by address links each to its own page.
Within the DC zone
14th of 40 zoned DC — the comparison that shares its rules, rents and streets.
40 of the screened buildings are zoned DC. 121 S Market St ranks 14th of them against a median score of 78. 24 score 70 or more, their median deepest interior point is 59 ft from a facade against this building’s 52 ft, and together they would hold an estimated 8,653 homes. The group’s top scorer is 1 Almaden Blvd, at 100.
Its nearest match in size: 84 W Santa Clara St
The screened building closest to 121 S Market St in converted floor area is 84 W Santa Clara St: 90,330 sq ft over 8 stories, against 89,050 sq ft over 9 here.
121 S Market St scores 84 to its 93, and with the size held roughly equal most of that shortfall comes from interior depth: 69 out of 100 here, 97 there (deepest interior point 41 ft from a facade, scored from 80 ft down to 40 ft). On the money they part ways: 84 W Santa Clara St pencils without a subsidy, while 121 S Market St pencils only with the modeled RESIDE grant. The two stand about 800 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 121 S Market St $5.0M, 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 121 S Market St
The 4 closest the screen also covers, from 250 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 250 ft away
- 125 S Market St13 stories · 79% daylit · 294 estimated homes · scores 78/100 (Strong candidate)about 270 ft away
- 100 W San Fernando St5 stories · 76% daylit · 100 estimated homes · scores 73/100 (Strong candidate)about 310 ft away
- 104 S Market St3 stories · 86% daylit · 47 estimated homes · scores 76/100 (Strong candidate)about 340 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.