990 Spring Garden St
990 Spring Garden St is a 7-story building in Center City Philadelphia with 76% of its floor area within daylight reach of a facade. This screen estimates 109 homes and scores it 63 out of 100 for office-to-residential conversion suitability.
PA-2 & PA-3 · Screened 2026-09-15 · Worth a feasibility study
Where 990 Spring Garden St is
Its block in Center City Philadelphia, drawn from Philadelphia's own building outlines and street centerlines.
- Already housing
- Not screened
- 990 Spring Garden St
This building does not pencil at default assumptions, even with a modeled RESIDE Act grant.
Every floor carries 5,341 sq ft of windowless core — area that must be gutted, re-plumbed and sprinklered but can never be rented as an apartment. Across 6 residential floors that is 32,044 sq ft of cost carrying no revenue.
Modeled conversion metrics for 990 Spring Garden St, 2026-09-15.
| Suitability scoreWorth a feasibility study | 63 / 100 |
|---|---|
| Storiesfrom 98 ft LiDAR height ÷ 12 ft floor-to-floor | 7 |
| Floor plateper floor, from the city footprint | 22,425 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 76% |
| Deepest interior pointviability threshold is 80 ft | 57 ft |
| Windowless coreper floor — renovated but never rentable | 5,341 sq ft |
| Estimated homesat 750 sq ft average | 109 |
| Conversion cost$360/sq ft all-in on 134,550 sq ft | $48.4M |
| Gap before grantshortfall against completed value | $27.0M |
| Modeled RESIDE grantbelow the statutory cap | $6.5M |
| BuiltPhiladelphia's own record of the construction year | 1920 |
| ZoningCenter City Philadelphia | CMX3 |
| Opportunity Zonecensus tract 42101037600, 2018 designation | Yes |
The plan: window line, shape and floor rhythm
36 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.
The typical floor has 656 ft of exterior wall, and across 6 residential floors the building carries 3,934 ft of it in total, divided among the 109 homes this screen estimates.
Its plate is moderately compact at 0.66: 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 18.2 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 990 Spring Garden St scores 63 out of 100
Daylight efficiency 72, Interior depth 58, Scale 73, Finance 30 — each out of 100, then weighted.
Score components for 990 Spring Garden St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency76% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 72 | 45% | 32.6 |
| Interior depthdeepest interior point 57 ft from a facade, scored from 80 ft down to 40 ft | 58 | 25% | 14.6 |
| Scale109 estimated homes, scored from 0 up to 150 | 73 | 15% | 10.9 |
| Financeremaining gap is 42% of conversion cost, scored from 60% down to 0% | 30 | 15% | 4.4 |
Most of what it earns comes from daylight efficiency, and what holds it back most is finance, at 30 out of 100: remaining gap is 42% of conversion cost, scored from 60% down to 0%.
Built in 1920
Philadelphia records this building as going up in 1920, which puts it in the interwar stock.
As a rule, steel or concrete frames with punched windows and plates still narrow enough for daylight to reach the middle, often with high ceilings. Among the most convertible stock there is, and the reason so many early conversions were of buildings this age. 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 76% daylight figure above deserves.
What the conversion would cost
$360 per square foot all-in across 134,550 sq ft of converted floor, or $48.4M in total — about $444K for each of the 109 homes.
All-in cost per square foot for 990 Spring Garden St: base cost plus the code work a change of use triggers.
| Base conversion cost | $260/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 | $360/sq ft |
That cost is charged across every converted square foot, including the 32,044 sq ft of windowless core, which has to be gutted, re-plumbed and sprinklered like the rest of the building and then earns nothing. Against it the model sets a completed value of $197K a home, which for 109 homes is $21.4M.
What would have to be true
A $27.0M gap before any grant, $20.5M after the modeled one. The smallest single change that would close it: average unit size 44% down.
The shortfall before any grant is $27.0M. Closing it from the value side means each of the 109 homes finishing at $444K rather than the $197K the model assumes — 126% more. Closing it from the cost side means getting all-in cost down from $360 to $159 per square foot.
A modeled RESIDE grant of $6.5M moves that threshold to $384K a home. That is still above the $197K assumed, leaving $20.5M uncovered, which is why the grant does not unlock this one.
Nor do all four levers have to move. For 990 Spring Garden St, one alone would close the gap at:
Single-assumption flip points for 990 Spring Garden St, each holding the other three at their defaults.
| Average unit sizethe binding constraint — the least this building would need | 44% downto 418 sq ft |
|---|---|
| Conversion cost per square foot | 58% downto $108/sq ft |
| Completed value per home | 95% upto $384K |
All four are sliders in the survey, where 990 Spring Garden St re-scores against your own numbers.
How it compares in Center City Philadelphia
990 Spring Garden St ranks 55th of the 103 buildings screened here, against a median score of 67.
Its floor plate is better lit than 46% of them, and shallower than 50% of them at its deepest interior point. On size it is the 70th largest by estimated homes. The full survey of all 103 buildings ranks and maps every one of them, and the list by address links each to its own page.
Within the CMX3 zone
9th of 14 zoned CMX3 — the comparison that shares its rules, rents and streets.
14 of the screened buildings are zoned CMX3. 990 Spring Garden St ranks 9th of them against a median score of 73. 8 score 70 or more, their median deepest interior point is 53 ft from a facade against this building’s 57 ft, and together they would hold an estimated 1,122 homes. The group’s top scorer is 461 N 3rd St, at 84.
Its nearest match in size: 2401 Walnut St
The screened building closest to 990 Spring Garden St in converted floor area is 2401 Walnut St: 138,098 sq ft over 8 stories, against 134,550 sq ft over 7 here.
990 Spring Garden St scores 63 to its 70, and with the size held roughly equal most of that shortfall comes from daylight efficiency: 72 out of 100 here, 79 there (80% 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 8,000 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 990 Spring Garden St $6.5M, 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 42101037600, a 2018 designated Opportunity Zone, which Section 201 lets HUD favor — one of the few statutory priorities this screen can actually check.
Other buildings screened near 990 Spring Garden St
The 4 closest the screen also covers, from 370 ft away. They are the colored outlines on the plan at the top of this page.
- 448 N 10th St7 stories · 100% daylit · 52 estimated homes · scores 84/100 (Strong candidate)about 370 ft away
- 1025 Callowhill St5 stories · 88% daylit · 50 estimated homes · scores 73/100 (Strong candidate)about 990 ft away
- 417 N 8th St5 stories · 85% daylit · 103 estimated homes · scores 72/100 (Strong candidate)about 1,150 ft away
- 319 N 11th St6 stories · 95% daylit · 44 estimated homes · scores 82/100 (Strong candidate)about 1,290 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.