1 Market St
1 Market St is a 11-story building in Downtown San Francisco with 84% of its floor area within daylight reach of a facade. This screen estimates 373 homes and scores it 83 out of 100 for office-to-residential conversion suitability.
CA-11 · Screened 2026-10-12 · Strong candidate
Also addressed as 11 Spear St, 25 Spear St, 35 Spear St and 45 Spear St: San Francisco’s address records place all 5 on this one footprint.
Where 1 Market St is
Its block in Downtown San Francisco, drawn from San Francisco's own building outlines and street centerlines.
- Already housing
- Not screened
- 1 Market St
This building does not pencil at default assumptions, even with a modeled RESIDE Act grant.
Every floor carries 6,906 sq ft of windowless core — area that must be gutted, seismically braced and sprinklered but can never be rented as an apartment. Across 10 residential floors that is 69,061 sq ft of cost carrying no revenue.
Read with caution. This footprint carries 5 street addresses across 41,965 sq ft, which usually means the city’s GIS has merged a block or complex into a single polygon rather than describing one convertible building.
Modeled conversion metrics for 1 Market St, 2026-10-12.
| Suitability scoreStrong candidate | 83 / 100 |
|---|---|
| Storiesfrom 151 ft LiDAR (2010) height ÷ 12 ft floor-to-floor | 11 |
| Floor plateper floor, from the city footprint | 41,965 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 84% |
| Deepest interior pointviability threshold is 80 ft | 52 ft |
| Windowless coreper floor — renovated but never rentable | 6,906 sq ft |
| Estimated homesat 750 sq ft average | 373 |
| Conversion cost$405/sq ft all-in on 419,650 sq ft | $170.0M |
| Gap before grantshortfall against completed value | $33.4M |
| Modeled RESIDE grantat the statutory per-award cap | $10.0M |
| BuiltSan Francisco's own record of the construction year | 1917 |
| ZoningFinancial District/South Beach | C-3-O(SD) |
| 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 1,273 ft of exterior wall, and across 10 residential floors the building carries 12,725 ft of it in total, divided among the 373 homes this screen estimates.
Its plate is elongated at 0.33: a slab or an L, which is why so much of the floor lies within reach of a window: the outline buys daylight that a square plan of the same area would not. How window line and plate shape are measured.
At the model’s 750 sq ft average, the plan works out at about 37.3 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 1 Market St scores 83 out of 100
Daylight efficiency 87, Interior depth 70, Scale 100, Finance 77 — each out of 100, then weighted.
Score components for 1 Market St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency84% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 87 | 45% | 39.2 |
| Interior depthdeepest interior point 52 ft from a facade, scored from 80 ft down to 40 ft | 70 | 25% | 17.5 |
| Scale373 estimated homes, scored from 0 up to 150 | 100 | 15% | 15.0 |
| Financeremaining gap is 14% of conversion cost, scored from 60% down to 0% | 77 | 15% | 11.6 |
Most of what it earns comes from daylight efficiency, and what holds it back most is interior depth, at 70 out of 100: deepest interior point 52 ft from a facade, scored from 80 ft down to 40 ft.
Built in 1917
San Francisco records this building as going up in 1917, 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 84% daylight figure above deserves.
What the conversion would cost
$405 per square foot all-in across 419,650 sq ft of converted floor, or $170.0M in total — about $456K for each of the 373 homes.
All-in cost per square foot for 1 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 69,061 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 373 homes is $136.5M.
What would have to be true
A $33.4M gap before any grant, $23.4M after the modeled one. The smallest single change that would close it: average unit size 15% down.
The shortfall before any grant is $33.4M. Closing it from the value side means each of the 373 homes finishing at $456K rather than the $366K the model assumes — 24% more. Closing it from the cost side means getting all-in cost down from $405 to $325 per square foot.
A modeled RESIDE grant of $10.0M moves that threshold to $429K a home. That is still above the $366K assumed, leaving $23.4M uncovered, which is why the grant does not unlock this one.
Nor do all four levers have to move. For 1 Market St, one alone would close the gap at:
Single-assumption flip points for 1 Market St, each holding the other three at their defaults.
| Average unit sizethe binding constraint — the least this building would need | 15% downto 640 sq ft |
|---|---|
| Circulation efficiency | 17% upto 94% |
| Completed value per home | 17% upto $429K |
| Conversion cost per square foot | 21% downto $204/sq ft |
All four are sliders in the survey, where 1 Market St re-scores against your own numbers.
How it compares in Downtown San Francisco
1 Market St ranks 115th of the 205 buildings screened here, against a median score of 87.
Its floor plate is better lit than 41% of them, and shallower than 44% of them at its deepest interior point. On size it is the 38th 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 Financial District/South Beach and the C-3-O(SD) zone
96th of 165 in Financial District/South Beach, 27th of 66 zoned C-3-O(SD) — the comparison that shares its rules, rents and streets.
San Francisco places 165 of the screened buildings in Financial District/South Beach. 1 Market St ranks 96th of them against a median score of 88. 121 score 70 or more, their median deepest interior point is 47 ft from a facade against this building’s 52 ft, and together they would hold an estimated 40,456 homes. The group’s top scorer is 870 Market St, at 100.
66 of the screened buildings are zoned C-3-O(SD). 1 Market St ranks 27th of them against a median score of 72. 37 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 18,546 homes. The group’s top scorer is 140 New Montgomery St, at 100.
Its nearest match in size: 101 Market St
The screened building closest to 1 Market St in converted floor area is 101 Market St: 386,849 sq ft over 12 stories, against 419,650 sq ft over 11 here.
1 Market St scores 83 to its 57, and with the size held roughly equal most of that lead comes from daylight efficiency: 87 out of 100 here, 53 there (66% of the floor area within 35 ft of a facade, scored from 40% up to 90%). On the money they sit in the same place: each falls short even with the modeled grant. The two stand about 400 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 1 Market St $10.0M, 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 1 Market St
The 4 closest the screen also covers, from 360 ft away. They are the colored outlines on the plan at the top of this page.
- 101 Market St12 stories · 66% daylit · 273 estimated homes · scores 57/100 (Worth a feasibility study)about 360 ft away
- 60 Spear St12 stories · 84% daylit · 140 estimated homes · scores 83/100 (Strong candidate)about 490 ft away
- 20 California St7 stories · 100% daylit · 58 estimated homes · scores 91/100 (Strong candidate)about 610 ft away
- 150 Drumm St45 stories · 63% daylit · 997 estimated homes · scores 35/100 (Marginal)about 640 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.