100 N 20th St

Where 100 N 20th 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

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 628 ft of exterior wall, and across 4 residential floors the building carries 2,510 ft of it in total, divided among the 69 homes this screen estimates.

Its plate is moderately compact at 0.71: 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 17.3 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.

Why 100 N 20th St scores 48 out of 100

Daylight efficiency 67, Interior depth 26, Scale 46, Finance 26 — each out of 100, then weighted.

Most of what it earns comes from daylight efficiency, and what holds it back most is finance, at 26 out of 100: remaining gap is 45% of conversion cost, scored from 60% down to 0%.

Built in 1981

Philadelphia records this building as going up in 1981, 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 88,866 sq ft of converted floor, or $32.0M in total — about $464K for each of the 69 homes.

That cost is charged across every converted square foot, including the 23,366 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 69 homes is $13.6M.

What would have to be true

A $18.4M gap before any grant, $14.3M after the modeled one. The smallest single change that would close it: average unit size 44% down.

The shortfall before any grant is $18.4M. Closing it from the value side means each of the 69 homes finishing at $464K rather than the $197K the model assumes — 136% more. Closing it from the cost side means getting all-in cost down from $360 to $153 per square foot.

A modeled RESIDE grant of $4.1M moves that threshold to $404K a home. That is still above the $197K assumed, leaving $14.3M uncovered, which is why the grant does not unlock this one.

Nor do all four levers have to move. For 100 N 20th St, one alone would close the gap at:

All four are sliders in the survey, where 100 N 20th St re-scores against your own numbers.

How it compares in Center City Philadelphia

100 N 20th St ranks 67th of the 103 buildings screened here, against a median score of 67.

Its floor plate is better lit than 39% of them, and shallower than 31% of them at its deepest interior point. On size it is the 76th 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

12th of 14 zoned CMX3 — the comparison that shares its rules, rents and streets.

14 of the screened buildings are zoned CMX3. 100 N 20th St ranks 12th 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 69 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: 105 S 7th St

The screened building closest to 100 N 20th St in converted floor area is 105 S 7th St: 98,203 sq ft over 4 stories, against 88,866 sq ft over 5 here.

100 N 20th St scores 48 to its 33, and with the size held roughly equal most of that lead comes from daylight efficiency: 67 out of 100 here, 47 there (63% 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 6,400 ft apart.

Would it qualify for a RESIDE Act grant?

The model awards 100 N 20th St $4.1M, 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 100 N 20th St

The 4 closest the screen also covers, from 660 ft away. They are the colored outlines on the plan at the top of this page.

• 2001 Market St
  41 stories · 60% daylit · 1,351 estimated homes · scores 33/100 (Marginal)
  about 660 ft away
• 2005 Market St
  40 stories · 61% daylit · 1,337 estimated homes · scores 34/100 (Marginal)
  about 720 ft away
• 2131 Arch St
  4 stories · 93% daylit · 27 estimated homes · scores 76/100 (Strong candidate)
  about 780 ft away
• 130 N 18th St
  30 stories · 85% daylit · 691 estimated homes · scores 80/100 (Strong candidate)
  about 810 ft away