517 S 4th St

Where 517 S 4th St is

Its block in Center City Philadelphia, drawn from Philadelphia's own building outlines and street centerlines.

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 432 ft of exterior wall, and across 4 residential floors the building carries 1,726 ft of it in total, divided among the 42 homes this screen estimates.

Its plate is compact at 0.74: 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 10.5 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.

Why 517 S 4th St scores 77 out of 100

Daylight efficiency 100, Interior depth 81, Scale 28, Finance 47 — each out of 100, then weighted.

Most of what it earns comes from daylight efficiency, and what holds it back most is scale, at 28 out of 100: 42 estimated homes, scored from 0 up to 150.

Built in 1900

Philadelphia records this building as going up in 1900, which puts it in the pre-1920 stock.

As a rule, the era that converts most readily: load-bearing masonry, small floor plates laid out before deep-plan offices were possible, operable windows and generous floor-to-floor heights. The usual obstacles are not daylight but hazardous materials, lifts and bringing structure up to current code. 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 91% daylight figure above deserves.

What the conversion would cost

$360 per square foot all-in across 43,834 sq ft of converted floor, or $15.8M in total — about $376K for each of the 42 homes.

That cost is charged across every converted square foot, including the 4,028 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 42 homes is $8.3M.

What would have to be true

A $7.5M gap before any grant, $5.0M after the modeled one. The smallest single change that would close it: average unit size 32% down.

The shortfall before any grant is $7.5M. Closing it from the value side means each of the 42 homes finishing at $376K rather than the $197K the model assumes — 91% more. Closing it from the cost side means getting all-in cost down from $360 to $188 per square foot.

A modeled RESIDE grant of $2.5M moves that threshold to $316K a home. That is still above the $197K assumed, leaving $5.0M uncovered, which is why the grant does not unlock this one.

Nor do all four levers have to move. For 517 S 4th St, one alone would close the gap at:

All four are sliders in the survey, where 517 S 4th St re-scores against your own numbers.

How it compares in Center City Philadelphia

517 S 4th St ranks 40th of the 103 buildings screened here, against a median score of 67.

Its floor plate is better lit than 68% of them, and shallower than 64% of them at its deepest interior point. On size it is the 90th 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

6th of 14 zoned CMX3 — the comparison that shares its rules, rents and streets.

14 of the screened buildings are zoned CMX3. 517 S 4th St ranks 6th 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 47 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: 123 Chestnut St

The screened building closest to 517 S 4th St in converted floor area is 123 Chestnut St: 43,972 sq ft over 4 stories, against 43,834 sq ft over 5 here.

517 S 4th St scores 77 to its 73, and with the size held roughly equal most of that lead comes from daylight efficiency: 100 out of 100 here, 96 there (88% 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 2,800 ft apart.

Would it qualify for a RESIDE Act grant?

The model awards 517 S 4th St $2.5M, 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.

It does not sit in a 2018 designated Opportunity Zone, so it would not draw that Section 201 priority.

Other buildings screened near 517 S 4th St

The 4 closest the screen also covers, from 1,840 ft away. They are the colored outlines on the plan at the top of this page.

• 700 Spruce St
  4 stories · 82% daylit · 129 estimated homes · scores 35/100 (Marginal)
  about 1,840 ft away
• 428 Walnut St
  9 stories · 74% daylit · 212 estimated homes · scores 58/100 (Worth a feasibility study)
  about 1,870 ft away
• 508 Walnut St
  20 stories · 48% daylit · 712 estimated homes · scores 23/100 (Unlikely)
  about 2,000 ft away
• 170 S Independence Mall W
  12 stories · 43% daylit · 476 estimated homes · scores 18/100 (Unlikely)
  about 2,430 ft away