1025 Callowhill St
1025 Callowhill St is a 5-story building in Center City Philadelphia with 88% of its floor area within daylight reach of a facade. This screen estimates 50 homes and scores it 73 out of 100 for office-to-residential conversion suitability.
PA-2 & PA-3 · Screened 2026-09-15 · Strong candidate
Where 1025 Callowhill St is
Its block in Center City Philadelphia, drawn from Philadelphia's own building outlines and street centerlines.
- Already housing
- Not screened
- 1025 Callowhill St
This building does not pencil at default assumptions, even with a modeled RESIDE Act grant.
Every floor carries 1,571 sq ft of windowless core — area that must be gutted, re-plumbed and sprinklered but can never be rented as an apartment. Across 4 residential floors that is 6,282 sq ft of cost carrying no revenue.
Modeled conversion metrics for 1025 Callowhill St, 2026-09-15.
| Suitability scoreStrong candidate | 73 / 100 |
|---|---|
| Storiesfrom 67 ft LiDAR height ÷ 12 ft floor-to-floor | 5 |
| Floor plateper floor, from the city footprint | 13,304 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 88% |
| Deepest interior pointviability threshold is 80 ft | 51 ft |
| Windowless coreper floor — renovated but never rentable | 1,571 sq ft |
| Estimated homesat 750 sq ft average | 50 |
| Conversion cost$360/sq ft all-in on 53,216 sq ft | $19.2M |
| Gap before grantshortfall against completed value | $9.3M |
| Modeled RESIDE grantbelow the statutory cap | $3.0M |
| BuiltPhiladelphia's own record of the construction year | 2008 |
| ZoningCenter City Philadelphia | RMX3 |
| Opportunity Zonecensus tract 42101037600, 2018 designation | Yes |
The plan: window line, shape and floor rhythm
43 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.
The typical floor has 533 ft of exterior wall, and across 4 residential floors the building carries 2,134 ft of it in total, divided among the 50 homes this screen estimates.
Its plate is moderately compact at 0.59: 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 12.5 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 1025 Callowhill St scores 73 out of 100
Daylight efficiency 96, Interior depth 72, Scale 33, Finance 45 — each out of 100, then weighted.
Score components for 1025 Callowhill St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency88% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 96 | 45% | 43.4 |
| Interior depthdeepest interior point 51 ft from a facade, scored from 80 ft down to 40 ft | 72 | 25% | 17.9 |
| Scale50 estimated homes, scored from 0 up to 150 | 33 | 15% | 5.0 |
| Financeremaining gap is 33% of conversion cost, scored from 60% down to 0% | 45 | 15% | 6.7 |
Most of what it earns comes from daylight efficiency, and what holds it back most is scale, at 33 out of 100: 50 estimated homes, scored from 0 up to 150.
Built in 2008
Philadelphia records this building as going up in 2008, 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 88% daylight figure above deserves.
What the conversion would cost
$360 per square foot all-in across 53,216 sq ft of converted floor, or $19.2M in total — about $383K for each of the 50 homes.
All-in cost per square foot for 1025 Callowhill 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 6,282 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 50 homes is $9.8M.
What would have to be true
A $9.3M gap before any grant, $6.3M after the modeled one. The smallest single change that would close it: average unit size 33% down.
The shortfall before any grant is $9.3M. Closing it from the value side means each of the 50 homes finishing at $383K rather than the $197K the model assumes — 95% more. Closing it from the cost side means getting all-in cost down from $360 to $185 per square foot.
A modeled RESIDE grant of $3.0M moves that threshold to $323K a home. That is still above the $197K assumed, leaving $6.3M uncovered, which is why the grant does not unlock this one.
Nor do all four levers have to move. For 1025 Callowhill St, one alone would close the gap at:
Single-assumption flip points for 1025 Callowhill St, each holding the other three at their defaults.
| Average unit sizethe binding constraint — the least this building would need | 33% downto 501 sq ft |
|---|---|
| Conversion cost per square foot | 46% downto $141/sq ft |
| Completed value per home | 64% upto $323K |
All four are sliders in the survey, where 1025 Callowhill St re-scores against your own numbers.
How it compares in Center City Philadelphia
1025 Callowhill St ranks 42nd of the 103 buildings screened here, against a median score of 67.
Its floor plate is better lit than 65% of them, and shallower than 58% of them at its deepest interior point. On size it is the 83rd 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.
Its nearest match in size: 461 N 3rd St
The screened building closest to 1025 Callowhill St in converted floor area is 461 N 3rd St: 50,410 sq ft over 5 stories, against 53,216 sq ft over 5 here.
1025 Callowhill St scores 73 to its 84, and with the size held roughly equal most of that shortfall comes from interior depth: 72 out of 100 here, 100 there (deepest interior point 35 ft from a facade, scored from 80 ft down to 40 ft). On the money they sit in the same place: each falls short even with the modeled grant. The two stand about 3,500 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 1025 Callowhill St $3.0M, 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 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 1025 Callowhill St
The 4 closest the screen also covers, from 310 ft away. They are the colored outlines on the plan at the top of this page.
- 319 N 11th St6 stories · 95% daylit · 44 estimated homes · scores 82/100 (Strong candidate)about 310 ft away
- 448 N 10th St7 stories · 100% daylit · 52 estimated homes · scores 84/100 (Strong candidate)about 610 ft away
- 990 Spring Garden St7 stories · 76% daylit · 109 estimated homes · scores 63/100 (Worth a feasibility study)about 990 ft away
- 417 N 8th St5 stories · 85% daylit · 103 estimated homes · scores 72/100 (Strong candidate)about 1,340 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.