901 Market St
901 Market St is a 5-story building in Downtown San Francisco with 64% of its floor area within daylight reach of a facade. This screen estimates 83 homes and scores it 35 out of 100 for office-to-residential conversion suitability.
CA-11 · Screened 2026-10-12 · Marginal
Where 901 Market St is
Its block in Downtown San Francisco, drawn from San Francisco's own building outlines and street centerlines.
- Already housing
- Not screened
- 901 Market St
This building does not pencil at default assumptions, even with a modeled RESIDE Act grant.
Every floor carries 10,957 sq ft of windowless core — area that must be gutted, seismically braced and sprinklered but can never be rented as an apartment. Across 4 residential floors that is 43,827 sq ft of cost carrying no revenue.
Modeled conversion metrics for 901 Market St, 2026-10-12.
| Suitability scoreMarginal | 35 / 100 |
|---|---|
| Storiesfrom 99 ft LiDAR (2010) height ÷ 12 ft floor-to-floor | 5 |
| Floor plateper floor, from the city footprint | 30,532 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 64% |
| Deepest interior pointviability threshold is 80 ft | 84 ft |
| Windowless coreper floor — renovated but never rentable | 10,957 sq ft |
| Estimated homesat 750 sq ft average | 83 |
| Conversion cost$405/sq ft all-in on 122,129 sq ft | $49.5M |
| Gap before grantshortfall against completed value | $19.1M |
| Modeled RESIDE grantbelow the statutory cap | $5.0M |
| BuiltSan Francisco's own record of the construction year | 1912 |
| ZoningSouth of Market | C-3-R |
| Opportunity Zonenot in a 2018 designated tract | No |
The plan: window line, shape and floor rhythm
34 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.
The typical floor has 700 ft of exterior wall, and across 4 residential floors the building carries 2,801 ft of it in total, divided among the 83 homes this screen estimates.
Its plate is compact at 0.78: 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 20.8 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 901 Market St scores 35 out of 100
The weighted components add to 38, but the score is capped at 35 because its deepest interior point is 84 ft from a facade, past the 80 ft threshold beyond which conversion requires carving a light well.
Score components for 901 Market St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency64% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 48 | 45% | 21.7 |
| Interior depthdeepest interior point 84 ft from a facade, scored from 80 ft down to 40 ft | 0 | 25% | 0.0 |
| Scale83 estimated homes, scored from 0 up to 150 | 55 | 15% | 8.3 |
| Financeremaining gap is 29% of conversion cost, scored from 60% down to 0% | 52 | 15% | 7.9 |
Most of what it earns comes from daylight efficiency, and what holds it back most is interior depth, at 0 out of 100: deepest interior point 84 ft from a facade, scored from 80 ft down to 40 ft.
Built in 1912
San Francisco records this building as going up in 1912, which puts it in the pre-1920 stock.
As a rule, the era that converts most readily: load-bearing masonry, small floor plates laid out before deep-plan offices were possible, operable windows and generous floor-to-floor heights. The usual obstacles are not daylight but hazardous materials, lifts and bringing structure up to current code. That is the era’s general tendency rather than a finding about this building — the model reads an outline and a height, and can see nothing inside — but it is the first thing an architect would want to know, and it colours how much confidence the 64% daylight figure above deserves.
What the conversion would cost
$405 per square foot all-in across 122,129 sq ft of converted floor, or $49.5M in total — about $596K for each of the 83 homes.
All-in cost per square foot for 901 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 43,827 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 $366K a home, which for 83 homes is $30.4M.
What would have to be true
A $19.1M gap before any grant, $14.1M after the modeled one. The smallest single change that would close it: average unit size 29% down.
The shortfall before any grant is $19.1M. Closing it from the value side means each of the 83 homes finishing at $596K rather than the $366K the model assumes — 63% more. Closing it from the cost side means getting all-in cost down from $405 to $249 per square foot.
A modeled RESIDE grant of $5.0M moves that threshold to $536K a home. That is still above the $366K assumed, leaving $14.1M uncovered, which is why the grant does not unlock this one.
Nor do all four levers have to move. For 901 Market St, one alone would close the gap at:
Single-assumption flip points for 901 Market St, each holding the other three at their defaults.
| Average unit sizethe binding constraint — the least this building would need | 29% downto 535 sq ft |
|---|---|
| Conversion cost per square foot | 44% downto $145/sq ft |
| Completed value per home | 46% upto $536K |
All four are sliders in the survey, where 901 Market St re-scores against your own numbers.
How it compares in Downtown San Francisco
901 Market St ranks 196th of the 205 buildings screened here, against a median score of 87.
Its floor plate is better lit than 4% of them, and shallower than 3% of them at its deepest interior point. On size it is the 134th largest by estimated homes. The full survey of all 205 buildings ranks and maps every one of them, and the list by address links each to its own page.
Within South of Market and the C-3-R zone
13th of 14 in South of Market, 25th of 25 zoned C-3-R — the comparison that shares its rules, rents and streets.
San Francisco places 14 of the screened buildings in South of Market. 901 Market St ranks 13th of them against a median score of 82. 9 score 70 or more, their median deepest interior point is 45 ft from a facade against this building’s 84 ft, and together they would hold an estimated 2,045 homes. The group’s top scorer is 431 Natoma St, at 100.
25 of the screened buildings are zoned C-3-R. 901 Market St ranks 25th of them against a median score of 90. 21 score 70 or more, their median deepest interior point is 32 ft from a facade against this building’s 84 ft, and together they would hold an estimated 2,773 homes. The group’s top scorer is 870 Market St, at 100.
Its nearest match in size: 138 Minna St
The screened building closest to 901 Market St in converted floor area is 138 Minna St: 125,768 sq ft over 9 stories, against 122,129 sq ft over 5 here.
138 Minna St scores 98 and 901 Market St only 35, and the difference is a hard fail rather than a matter of degree: the lower one is capped at 35 because its deepest interior point is 84 ft from a facade, past the 80 ft threshold beyond which conversion requires carving a light well. On the money they part ways: 138 Minna St pencils only with the modeled RESIDE grant, while 901 Market St falls short even with the modeled grant. The two stand about 2,500 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 901 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.
It does not sit in a 2018 designated Opportunity Zone, so it would not draw that Section 201 priority.
Other buildings screened near 901 Market St
The 4 closest the screen also covers, from 320 ft away. They are the colored outlines on the plan at the top of this page.
- 25 Cyril Magnin St8 stories · 100% daylit · 66 estimated homes · scores 92/100 (Strong candidate)about 320 ft away
- 979 Market St6 stories · 82% daylit · 75 estimated homes · scores 75/100 (Strong candidate)about 610 ft away
- 870 Market St12 stories · 100% daylit · 324 estimated homes · scores 100/100 (Strong candidate)about 620 ft away
- 479 Jessie St4 stories · 100% daylit · 26 estimated homes · scores 88/100 (Strong candidate)about 710 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.