101 1st St
101 1st St is a 63-story building in Downtown San Francisco with 59% of its floor area within daylight reach of a facade. This screen estimates 1,457 homes and scores it 35 out of 100 for office-to-residential conversion suitability.
CA-11 · Screened 2026-10-12 · Marginal
Also addressed as 415 Mission St: San Francisco’s address records place both on this one footprint.
Where 101 1st St is
Its block in Downtown San Francisco, drawn from San Francisco's own building outlines and street centerlines.
- Already housing
- Not screened
- 101 1st St
This building does not pencil at default assumptions, even with a modeled RESIDE Act grant.
Every floor carries 15,008 sq ft of windowless core — area that must be gutted, seismically braced and sprinklered but can never be rented as an apartment. Across 62 residential floors that is 930,522 sq ft of cost carrying no revenue.
Height not confirmed. The city's 2010 LiDAR survey records this footprint at ground level, which usually means the building went up after 2010. The model uses the 63 floors on the 2025 Assessor roll and draws the building 756 ft tall from them.
Modeled conversion metrics for 101 1st St, 2026-10-12.
| Suitability scoreMarginal | 35 / 100 |
|---|---|
| Storiesfrom 756 ft LiDAR (2010) height ÷ 12 ft floor-to-floor | 63 |
| Floor plateper floor, from the city footprint | 37,042 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 59% |
| Deepest interior pointviability threshold is 80 ft | 93 ft |
| Windowless coreper floor — renovated but never rentable | 15,008 sq ft |
| Estimated homesat 750 sq ft average | 1,457 |
| Conversion cost$405/sq ft all-in on 2,296,587 sq ft | $930.1M |
| Gap before grantshortfall against completed value | $396.9M |
| Modeled RESIDE grantat the statutory per-award cap | $10.0M |
| BuiltSan Francisco's own record of the construction year | 2018 |
| ZoningFinancial District/South Beach | C-3-O(SD) |
| Opportunity Zonenot in a 2018 designated tract | No |
The plan: window line, shape and floor rhythm
33 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.
The typical floor has 769 ft of exterior wall, and across 62 residential floors the building carries 47,660 ft of it in total, divided among the 1,457 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 23.5 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 101 1st St scores 35 out of 100
The weighted components add to 37, but the score is capped at 35 because its deepest interior point is 93 ft from a facade, past the 80 ft threshold beyond which conversion requires carving a light well.
Score components for 101 1st St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency59% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 39 | 45% | 17.5 |
| Interior depthdeepest interior point 93 ft from a facade, scored from 80 ft down to 40 ft | 0 | 25% | 0.0 |
| Scale1457 estimated homes, scored from 0 up to 150 | 100 | 15% | 15.0 |
| Financeremaining gap is 42% of conversion cost, scored from 60% down to 0% | 31 | 15% | 4.6 |
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 93 ft from a facade, scored from 80 ft down to 40 ft.
Built in 2018
San Francisco records this building as going up in 2018, which puts it in the modern stock.
As a rule, newer systems and better structure, but usually built deep and sealed for office use, and rarely cheap enough to buy at a price that lets a conversion pencil. 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 59% daylight figure above deserves.
What the conversion would cost
$405 per square foot all-in across 2,296,587 sq ft of converted floor, or $930.1M in total — about $638K for each of the 1,457 homes.
All-in cost per square foot for 101 1st 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 930,522 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 1,457 homes is $533.3M.
What would have to be true
A $396.9M gap before any grant, $386.9M after the modeled one. The smallest single change that would close it: average unit size 42% down.
The shortfall before any grant is $396.9M. Closing it from the value side means each of the 1,457 homes finishing at $638K rather than the $366K the model assumes — 74% more. Closing it from the cost side means getting all-in cost down from $405 to $232 per square foot.
A modeled RESIDE grant of $10.0M moves that threshold to $632K a home. That is still above the $366K assumed, leaving $386.9M uncovered, which is why the grant does not unlock this one.
Nor do all four levers have to move. For 101 1st St, one alone would close the gap at:
Single-assumption flip points for 101 1st St, each holding the other three at their defaults.
| Average unit sizethe binding constraint — the least this building would need | 42% downto 435 sq ft |
|---|---|
| Conversion cost per square foot | 65% downto $92/sq ft |
| Completed value per home | 73% upto $632K |
All four are sliders in the survey, where 101 1st St re-scores against your own numbers.
How it compares in Downtown San Francisco
101 1st St ranks 196th of the 205 buildings screened here, against a median score of 87.
Its floor plate is better lit than 2% of them, and shallower than 2% of them at its deepest interior point. On size it is the 2nd 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
160th of 165 in Financial District/South Beach, 63rd 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. 101 1st St ranks 160th 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 93 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). 101 1st St ranks 63rd 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 93 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 California St
The screened building closest to 101 1st St in converted floor area is 101 California St: 2,094,832 sq ft over 48 stories, against 2,296,587 sq ft over 63 here.
The two land within a few points of each other — 35 here, 35 there — so at this size the screen reads them as much the same prospect. On the money they sit in the same place: each falls short even with the modeled grant. The two stand about 1,200 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 101 1st 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 101 1st St
The 4 closest the screen also covers, from 230 ft away. They are the colored outlines on the plan at the top of this page.
- 440 Mission St5 stories · 82% daylit · 51 estimated homes · scores 70/100 (Strong candidate)about 230 ft away
- 100 1st St27 stories · 73% daylit · 443 estimated homes · scores 60/100 (Worth a feasibility study)about 250 ft away
- 75 1st St42 stories · 73% daylit · 671 estimated homes · scores 64/100 (Worth a feasibility study)about 280 ft away
- 400 Howard St10 stories · 62% daylit · 237 estimated homes · scores 35/100 (Marginal)about 380 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.