1601 Market St
1601 Market St is a 36-story building in Center City Philadelphia with 74% of its floor area within daylight reach of a facade. This screen estimates 702 homes and scores it 61 out of 100 for office-to-residential conversion suitability.
PA-2 & PA-3 · Screened 2026-09-15 · Worth a feasibility study
Also addressed as 1603 Market St, 1605 Market St, 1607 Market St, 1609 Market St, 1611 Market St, 1613 Market St, 1615 Market St, 1617 Market St, 1619 Market St, 1621 Market St and 1623 Market St: Philadelphia’s address records place all 12 on this one footprint.
Where 1601 Market St is
Its block in Center City Philadelphia, drawn from Philadelphia's own building outlines and street centerlines.
- Already housing
- Not screened
- 1601 Market St
This building does not pencil at default assumptions, even with a modeled RESIDE Act grant.
Every floor carries 6,563 sq ft of windowless core — area that must be gutted, re-plumbed and sprinklered but can never be rented as an apartment. Across 35 residential floors that is 229,722 sq ft of cost carrying no revenue.
Modeled conversion metrics for 1601 Market St, 2026-09-15.
| Suitability scoreWorth a feasibility study | 61 / 100 |
|---|---|
| Storiesfrom 481 ft LiDAR height ÷ 12 ft floor-to-floor | 36 |
| Floor plateper floor, from the city footprint | 25,371 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 74% |
| Deepest interior pointviability threshold is 80 ft | 58 ft |
| Windowless coreper floor — renovated but never rentable | 6,563 sq ft |
| Estimated homesat 750 sq ft average | 702 |
| Conversion cost$360/sq ft all-in on 887,997 sq ft | $319.7M |
| Gap before grantshortfall against completed value | $181.6M |
| Modeled RESIDE grantat the statutory per-award cap | $10.0M |
| BuiltPhiladelphia's own record of the construction year | 1970 |
| ZoningCenter City Philadelphia | CMX5 |
| Opportunity Zonenot in a 2018 designated tract | No |
The plan: window line, shape and floor rhythm
34 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.
The typical floor has 683 ft of exterior wall, and across 35 residential floors the building carries 23,922 ft of it in total, divided among the 702 homes this screen estimates.
Its plate is moderately compact at 0.68: 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 20.1 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 1601 Market St scores 61 out of 100
Daylight efficiency 68, Interior depth 54, Scale 100, Finance 11 — each out of 100, then weighted.
Score components for 1601 Market St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency74% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 68 | 45% | 30.7 |
| Interior depthdeepest interior point 58 ft from a facade, scored from 80 ft down to 40 ft | 54 | 25% | 13.5 |
| Scale702 estimated homes, scored from 0 up to 150 | 100 | 15% | 15.0 |
| Financeremaining gap is 54% of conversion cost, scored from 60% down to 0% | 11 | 15% | 1.6 |
Most of what it earns comes from daylight efficiency, and what holds it back most is finance, at 11 out of 100: remaining gap is 54% of conversion cost, scored from 60% down to 0%.
Built in 1970
Philadelphia records this building as going up in 1970, 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 74% daylight figure above deserves.
What the conversion would cost
$360 per square foot all-in across 887,997 sq ft of converted floor, or $319.7M in total — about $455K for each of the 702 homes.
All-in cost per square foot for 1601 Market 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 229,722 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 702 homes is $138.1M.
What would have to be true
A $181.6M gap before any grant, $171.6M after the modeled one. The smallest single change that would close it: average unit size 55% down.
The shortfall before any grant is $181.6M. Closing it from the value side means each of the 702 homes finishing at $455K rather than the $197K the model assumes — 132% more. Closing it from the cost side means getting all-in cost down from $360 to $155 per square foot.
A modeled RESIDE grant of $10.0M moves that threshold to $441K a home. That is still above the $197K assumed, leaving $171.6M uncovered, which is why the grant does not unlock this one.
Nor do all four levers have to move. For 1601 Market St, one alone would close the gap at:
Single-assumption flip points for 1601 Market St, each holding the other three at their defaults.
| Average unit sizethe binding constraint — the least this building would need | 55% downto 334 sq ft |
|---|---|
| Conversion cost per square foot | 74% downto $67/sq ft |
| Completed value per home | 124% upto $441K |
All four are sliders in the survey, where 1601 Market St re-scores against your own numbers.
How it compares in Center City Philadelphia
1601 Market St ranks 58th of the 103 buildings screened here, against a median score of 67.
Its floor plate is better lit than 41% of them, and shallower than 48% of them at its deepest interior point. On size it is the 15th 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 CMX5 zone
36th of 65 zoned CMX5 — the comparison that shares its rules, rents and streets.
65 of the screened buildings are zoned CMX5. 1601 Market St ranks 36th of them against a median score of 67. 28 score 70 or more, their median deepest interior point is 58 ft from a facade against this building’s 58 ft, and together they would hold an estimated 30,650 homes. The group’s top scorer is 112 N Broad St, at 93.
Its nearest match in size: 1600 Market St
The screened building closest to 1601 Market St in converted floor area is 1600 Market St: 881,431 sq ft over 39 stories, against 887,997 sq ft over 36 here.
1601 Market St scores 61 to its 55, and with the size held roughly equal most of that lead comes from interior depth: 54 out of 100 here, 27 there (deepest interior point 69 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 200 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 1601 Market 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 1601 Market St
The 4 closest the screen also covers, from 170 ft away. They are the colored outlines on the plan at the top of this page.
- 1600 John F Kennedy Blvd20 stories · 75% daylit · 414 estimated homes · scores 61/100 (Worth a feasibility study)about 170 ft away
- 1625 Market St19 stories · 81% daylit · 270 estimated homes · scores 67/100 (Worth a feasibility study)about 220 ft away
- 1600 Market St39 stories · 75% daylit · 702 estimated homes · scores 55/100 (Worth a feasibility study)about 220 ft away
- 1628 John F Kennedy Blvd23 stories · 90% daylit · 246 estimated homes · scores 88/100 (Strong candidate)about 280 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.