1225 Locust St
1225 Locust St is a 5-story building in Center City Philadelphia with 87% of its floor area within daylight reach of a facade. This screen estimates 44 homes and scores it 69 out of 100 for office-to-residential conversion suitability.
PA-2 & PA-3 · Screened 2026-09-15 · Worth a feasibility study
Also addressed as 1227 Locust St, 1229 Locust St, 1231 Locust St and 1233 Locust St: Philadelphia’s address records place all 5 on this one footprint.
Where 1225 Locust St is
Its block in Center City Philadelphia, drawn from Philadelphia's own building outlines and street centerlines.
- Already housing
- Not screened
- 1225 Locust St
This building does not pencil at default assumptions, even with a modeled RESIDE Act grant.
Every floor carries 1,558 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 6,233 sq ft of cost carrying no revenue.
Modeled conversion metrics for 1225 Locust St, 2026-09-15.
| Suitability scoreWorth a feasibility study | 69 / 100 |
|---|---|
| Storiesfrom 71 ft LiDAR height ÷ 12 ft floor-to-floor | 5 |
| Floor plateper floor, from the city footprint | 12,039 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 87% |
| Deepest interior pointviability threshold is 80 ft | 54 ft |
| Windowless coreper floor — renovated but never rentable | 1,558 sq ft |
| Estimated homesat 750 sq ft average | 44 |
| Conversion cost$360/sq ft all-in on 48,158 sq ft | $17.3M |
| Gap before grantshortfall against completed value | $8.7M |
| Modeled RESIDE grantbelow the statutory cap | $2.6M |
| BuiltPhiladelphia's own record of the construction year | 1980 |
| ZoningCenter City Philadelphia | CMX5 |
| Opportunity Zonenot in a 2018 designated tract | No |
The plan: window line, shape and floor rhythm
41 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.
The typical floor has 446 ft of exterior wall, and across 4 residential floors the building carries 1,785 ft of it in total, divided among the 44 homes this screen estimates.
Its plate is compact at 0.76: 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 11.0 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 1225 Locust St scores 69 out of 100
Daylight efficiency 94, Interior depth 65, Scale 29, Finance 42 — each out of 100, then weighted.
Score components for 1225 Locust St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency87% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 94 | 45% | 42.4 |
| Interior depthdeepest interior point 54 ft from a facade, scored from 80 ft down to 40 ft | 65 | 25% | 16.3 |
| Scale44 estimated homes, scored from 0 up to 150 | 29 | 15% | 4.4 |
| Financeremaining gap is 35% of conversion cost, scored from 60% down to 0% | 42 | 15% | 6.3 |
Most of what it earns comes from daylight efficiency, and what holds it back most is scale, at 29 out of 100: 44 estimated homes, scored from 0 up to 150.
Built in 1980
Philadelphia records this building as going up in 1980, 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 87% daylight figure above deserves.
What the conversion would cost
$360 per square foot all-in across 48,158 sq ft of converted floor, or $17.3M in total — about $394K for each of the 44 homes.
All-in cost per square foot for 1225 Locust 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 6,233 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 44 homes is $8.7M.
What would have to be true
A $8.7M gap before any grant, $6.0M after the modeled one. The smallest single change that would close it: average unit size 34% down.
The shortfall before any grant is $8.7M. Closing it from the value side means each of the 44 homes finishing at $394K rather than the $197K the model assumes — 100% more. Closing it from the cost side means getting all-in cost down from $360 to $180 per square foot.
A modeled RESIDE grant of $2.6M moves that threshold to $334K a home. That is still above the $197K assumed, leaving $6.0M uncovered, which is why the grant does not unlock this one.
Nor do all four levers have to move. For 1225 Locust St, one alone would close the gap at:
Single-assumption flip points for 1225 Locust St, each holding the other three at their defaults.
| Average unit sizethe binding constraint — the least this building would need | 34% downto 493 sq ft |
|---|---|
| Conversion cost per square foot | 48% downto $135/sq ft |
| Completed value per home | 70% upto $334K |
All four are sliders in the survey, where 1225 Locust St re-scores against your own numbers.
How it compares in Center City Philadelphia
1225 Locust St ranks 48th of the 103 buildings screened here, against a median score of 67.
Its floor plate is better lit than 62% of them, and shallower than 53% of them at its deepest interior point. On size it is the 88th 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
29th of 65 zoned CMX5 — the comparison that shares its rules, rents and streets.
65 of the screened buildings are zoned CMX5. 1225 Locust St ranks 29th 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 54 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: 2213 Chestnut St
The screened building closest to 1225 Locust St in converted floor area is 2213 Chestnut St: 49,088 sq ft over 5 stories, against 48,158 sq ft over 5 here.
The two land within a few points of each other — 69 here, 71 there — so at this size the screen reads them as much the same prospect. On the money they sit in the same place: each falls short even with the modeled grant. The two stand about 4,800 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 1225 Locust St $2.6M, 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 1225 Locust St
The 4 closest the screen also covers, from 630 ft away. They are the colored outlines on the plan at the top of this page.
- 1313 Walnut St18 stories · 100% daylit · 271 estimated homes · scores 92/100 (Strong candidate)about 630 ft away
- 213 S Broad St10 stories · 100% daylit · 74 estimated homes · scores 86/100 (Strong candidate)about 670 ft away
- 1326 Chestnut St8 stories · 100% daylit · 76 estimated homes · scores 87/100 (Strong candidate)about 890 ft away
- 230 S Broad St20 stories · 100% daylit · 253 estimated homes · scores 93/100 (Strong candidate)about 940 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.