21 1st St

Where 21 1st St is

Its block in Downtown San Francisco, drawn from San Francisco's own building outlines and street centerlines.

The plan: window line, shape and floor rhythm

38 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.

The typical floor has 502 ft of exterior wall, and across 22 residential floors the building carries 11,033 ft of it in total, divided among the 291 homes this screen estimates.

Its plate is compact at 0.75: 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 13.2 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.

Why 21 1st St scores 81 out of 100

Daylight efficiency 86, Interior depth 60, Scale 100, Finance 79 — each out of 100, then weighted.

Most of what it earns comes from daylight efficiency, and what holds it back most is interior depth, at 60 out of 100: deepest interior point 56 ft from a facade, scored from 80 ft down to 40 ft.

Built in 1988

San Francisco records this building as going up in 1988, which puts it in the late-modern stock.

As a rule, typically the hardest to convert: the deepest plates of any era, large central cores, and floor-to-floor heights tight enough that running residential drainage under a ceiling can be the thing that ends a project. 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 83% daylight figure above deserves.

What the conversion would cost

$405 per square foot all-in across 329,687 sq ft of converted floor, or $133.5M in total — about $459K for each of the 291 homes.

That cost is charged across every converted square foot, including the 56,055 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 291 homes is $106.5M.

What would have to be true

A $27.0M gap before any grant, $17.0M after the modeled one. The smallest single change that would close it: average unit size 14% down.

The shortfall before any grant is $27.0M. Closing it from the value side means each of the 291 homes finishing at $459K rather than the $366K the model assumes — 25% more. Closing it from the cost side means getting all-in cost down from $405 to $323 per square foot.

A modeled RESIDE grant of $10.0M moves that threshold to $424K a home. That is still above the $366K assumed, leaving $17.0M uncovered, which is why the grant does not unlock this one.

Nor do all four levers have to move. For 21 1st St, one alone would close the gap at:

All four are sliders in the survey, where 21 1st St re-scores against your own numbers.

How it compares in Downtown San Francisco

21 1st St ranks 127th of the 205 buildings screened here, against a median score of 87.

Its floor plate is better lit than 40% of them, and shallower than 38% of them at its deepest interior point. On size it is the 56th 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

106th of 165 in Financial District/South Beach, 29th 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. 21 1st St ranks 106th 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 56 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). 21 1st St ranks 29th 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 56 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: 150 California St

The screened building closest to 21 1st St in converted floor area is 150 California St: 328,336 sq ft over 23 stories, against 329,687 sq ft over 23 here.

21 1st St scores 81 to its 99, and with the size held roughly equal most of that shortfall comes from interior depth: 60 out of 100 here, 94 there (deepest interior point 42 ft from a facade, scored from 80 ft down to 40 ft). On the money they part ways: 150 California St pencils only with the modeled RESIDE grant, while 21 1st St falls short even with the modeled grant. The two stand about 1,100 ft apart.

Would it qualify for a RESIDE Act grant?

The model awards 21 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 21 1st St

The 4 closest the screen also covers, from 180 ft away. They are the colored outlines on the plan at the top of this page.

• 425 Market St
  38 stories · 68% daylit · 749 estimated homes · scores 55/100 (Worth a feasibility study)
  about 180 ft away
• 525 Market St
  38 stories · 66% daylit · 748 estimated homes · scores 46/100 (Marginal)
  about 270 ft away
• 440 Mission St
  5 stories · 82% daylit · 51 estimated homes · scores 70/100 (Strong candidate)
  about 290 ft away
• 75 1st St
  42 stories · 73% daylit · 671 estimated homes · scores 64/100 (Worth a feasibility study)
  about 300 ft away