1 S Market St

1 S Market St is a 22-story apartment building in Downtown San Jose. Its floor plate has 57% of its area within daylight reach of a facade and scores 35 out of 100 on this screen’s measures, which is part of why it works as housing.

CA-18 · Screened 2026-10-20 · Already housing

Also addressed as 142 W Santa Clara St: San Jose’s address records place both on this one footprint.

Where 1 S Market 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
1 S Market St

1 S Market 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. 1 S Market 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: 57% 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: 18,315 sq ft per floor that must be renovated but can never be rented as an apartment. The dimension marks the deepest interior point, 96 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: 18,315 sq ft on the floor the screen scores, and 384,606 sq ft over 21 residential floors. The shaded ground floor is converted like the rest and counted as no homes.

This is already an apartment building: San Jose's rental housing and condominium records list 320 apartments here, and OpenStreetMap maps it as an apartment building. It is on the map because downtown zoning permits offices and homes alike, but this site does not count it as a conversion candidate.

Every floor carries 18,315 sq ft of windowless core — area that must be gutted, seismically braced and sprinklered but can never be rented as an apartment. Across 21 residential floors that is 384,606 sq ft of cost carrying no revenue.

Separated from its neighbors. The city’s map draws this building and the ones beside it as one outline with one height. This outline comes from OpenStreetMap, which maps them separately, and its height is OpenStreetMap’s.

Modeled conversion metrics for 1 S Market St, 2026-10-20.

Suitability scoreMarginal	35 / 100
Storiesfrom OpenStreetMap, “One South Market, way 338746229”, in place of the 240 ft LiDAR height ÷ 12 ft floor-to-floor	22
Floor plateper floor, from the city footprint	42,286 sq ft
Daylight efficiencyshare within 35 ft of a facade	57%
Deepest interior pointviability threshold is 80 ft	96 ft
Windowless coreper floor — renovated but never rentable	18,315 sq ft
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

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

The typical floor has 825 ft of exterior wall, and across 21 residential floors the building carries 17,324 ft of it in total, divided among the 536 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 25.5 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.

Why 1 S Market 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 96 ft from a facade, past the 80 ft threshold beyond which conversion requires carving a light well.

Score components for 1 S Market St. Points are the subscore times its weight.

Component	Subscore	Weight	Points
Daylight efficiency57% of the floor area within 35 ft of a facade, scored from 40% up to 90%	33	45%	15.0
Interior depthdeepest interior point 96 ft from a facade, scored from 80 ft down to 40 ft	0	25%	0.0
Scale536 estimated homes, scored from 0 up to 150	100	15%	15.0
Financeremaining gap is 34% of conversion cost, scored from 60% down to 0%	44	15%	6.5

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 96 ft from a facade, scored from 80 ft down to 40 ft.

Other buildings screened near 1 S Market St

The 4 closest the screen also covers, from 240 ft away. They are the colored outlines on the plan at the top of this page.

160 W Santa Clara St
16 stories · 62% daylit · 341 estimated homes · scores 35/100 (Marginal)
about 240 ft away
84 W Santa Clara St
8 stories · 92% daylit · 88 estimated homes · scores 93/100 (Strong candidate)
about 250 ft away
81 Post St
7 stories · 100% daylit · 38 estimated homes · scores 89/100 (Strong candidate)
about 290 ft away
51 S Market St
15 stories · 67% daylit · 292 estimated homes · scores 52/100 (Worth a feasibility study)
about 310 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.