25 Post St

25 Post St is a 12-story building in Downtown San Jose with 49% of its floor area within daylight reach of a facade. This screen estimates 460 homes and scores it 28 out of 100 for office-to-residential conversion suitability.

CA-18 · Screened 2026-09-12 · Unlikely

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Also addressed as 27 Post St, 31 Post St, 39 Post St and 41 Post St: San Jose’s address records place all 5 on this one footprint.

Where 25 Post St is

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

Suitability score

0–29

30–49

50–69

70–100

Already housing
Not screened
25 Post St

25 Post St and the 1,000 ft of Downtown San Jose around it. The streets are drawn at the width of the right-of-way they run down, sidewalks included, and named, and every building on these blocks is drawn. What is left open and stippled is neither: a surface lot, a plaza or a vacant parcel. The screened buildings are colored by the ramp above, the same one the district map uses, carry their score, and each is a link to its own page. Each casts a shadow as long as its measured height lets it, so towers stand out from the low buildings around them; the unscreened buildings have no measured height and cast none. 25 Post St is outlined in its own score color at the outline it covers at ground level. Its windowless core is hatched. The inset places it among every building the screen covers.

Floor plan: 49% of each floor sits within daylight reach of a facade. The shading is daylight, darkest at the windows and gone 35 ft in. The hatched area is windowless core: 40,701 sq ft per floor that must be renovated but can never be rented as an apartment. The dimension marks the deepest interior point, 116 ft from the nearest window. A–A is where the section beside it is cut.

Section A–A: cut across the depth of the plate, through the middle of the core. Daylight reaches 35 ft in from every facade, fading as it goes, and the hatched stripe left between the lit edges is floor that gets converted and can never be rented: 40,701 sq ft on the floor the screen scores, and 447,714 sq ft over 11 residential floors. The shaded ground floor is converted like the rest and counted as no homes.

This building does not pencil at default assumptions, even with a modeled RESIDE Act grant.

Every floor carries 40,701 sq ft of windowless core — area that must be gutted, seismically braced and sprinklered but can never be rented as an apartment. Across 11 residential floors that is 447,714 sq ft of cost carrying no revenue.

Read with caution. This footprint carries 28 street addresses across 79,946 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 25 Post St, 2026-09-12.

Suitability scoreUnlikely	28 / 100
Storiesfrom 144 ft LiDAR height ÷ 12 ft floor-to-floor	12
Floor plateper floor, from the city footprint	79,946 sq ft
Daylight efficiencyshare within 35 ft of a facade	49%
Deepest interior pointviability threshold is 80 ft	116 ft
Windowless coreper floor — renovated but never rentable	40,701 sq ft
Estimated homesat 750 sq ft average	460
Conversion cost$405/sq ft all-in on 879,410 sq ft	$356.2M
Gap before grantshortfall against completed value	$160.7M
Modeled RESIDE grantat the statutory per-award cap	$10.0M
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

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

The typical floor has 1,316 ft of exterior wall, and across 11 residential floors the building carries 14,474 ft of it in total, divided among the 460 homes this screen estimates.

Its plate is moderately compact at 0.58: a squarish plan, with enough perimeter for a conventional double-loaded corridor. How window line and plate shape are measured.

At the model’s 750 sq ft average, the plan works out at about 41.8 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.

Why 25 Post St scores 28 out of 100

Daylight efficiency 18, Interior depth 0, Scale 100, Finance 29 — each out of 100, then weighted.

Score components for 25 Post St. Points are the subscore times its weight.

Component	Subscore	Weight	Points
Daylight efficiency49% of the floor area within 35 ft of a facade, scored from 40% up to 90%	18	45%	8.2
Interior depthdeepest interior point 116 ft from a facade, scored from 80 ft down to 40 ft	0	25%	0.0
Scale460 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%	29	15%	4.4

Most of what it earns comes from scale, and what holds it back most is interior depth, at 0 out of 100: deepest interior point 116 ft from a facade, scored from 80 ft down to 40 ft.

What the conversion would cost

$405 per square foot all-in across 879,410 sq ft of converted floor, or $356.2M in total — about $774K for each of the 460 homes.

All-in cost per square foot for 25 Post 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 447,714 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 460 homes is $195.5M.

What would have to be true

A $160.7M gap before any grant, $150.7M after the modeled one. The smallest single change that would close it: average unit size 44% down.

The shortfall before any grant is $160.7M. Closing it from the value side means each of the 460 homes finishing at $774K rather than the $425K the model assumes — 82% more. Closing it from the cost side means getting all-in cost down from $405 to $222 per square foot.

A modeled RESIDE grant of $10.0M moves that threshold to $753K a home. That is still above the $425K assumed, leaving $150.7M uncovered, which is why the grant does not unlock this one.

Nor do all four levers have to move. For 25 Post St, one alone would close the gap at:

Single-assumption flip points for 25 Post St, each holding the other three at their defaults.

Average unit sizethe binding constraint — the least this building would need	44% downto 424 sq ft
Conversion cost per square foot	66% downto $89/sq ft
Completed value per home	77% upto $753K

All four are sliders in the survey, where 25 Post St re-scores against your own numbers.

How it compares in Downtown San Jose

25 Post St ranks 76th of the 82 buildings screened here, against a median score of 64.

Its floor plate is better lit than 9% of them, and shallower than 10% of them at its deepest interior point. On size it is the 19th largest by estimated homes. The full survey of all 82 buildings ranks and maps every one of them, and the list by address links each to its own page.

Within the DC zone

66th of 72 zoned DC — the comparison that shares its rules, rents and streets.

72 of the screened buildings are zoned DC. 25 Post St ranks 66th of them against a median score of 61. 31 score 70 or more, their median deepest interior point is 68 ft from a facade against this building’s 116 ft, and together they would hold an estimated 23,276 homes. The group’s top scorer is 1 Almaden Blvd, at 100.

Its nearest match in size: 333 W Santa Clara St

The screened building closest to 25 Post St in converted floor area is 333 W Santa Clara St: 969,474 sq ft over 14 stories, against 879,410 sq ft over 12 here.

25 Post St scores 28 to its 35, and with the size held roughly equal most of that shortfall comes from daylight efficiency: 18 out of 100 here, 31 there (55% 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 1,700 ft apart.

Would it qualify for a RESIDE Act grant?

The model awards 25 Post 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.

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.