93-101 Arch St

Where 93-101 Arch St is

Its block in Downtown Boston, drawn from Boston'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 561 ft of exterior wall, and across 21 residential floors the building carries 14,029 ft of it in total, divided among the 389 homes this screen estimates.

Its plate is compact at 0.73: 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 18.5 homes per floor. Its floors are not alike, though: the typical floor's deepest interior point is 61 ft from a facade, while its worst floor reaches 79 ft. The score follows the typical floor, so a podium that could not hold a bedroom does not by itself sink a slim tower above it — but it is there, and it is part of what would have to be drawn around.

Why 93-101 Arch St scores 72 out of 100

Daylight efficiency 68, Interior depth 47, Scale 100, Finance 100 — each out of 100, then weighted.

Most of what it earns comes from daylight efficiency, and what holds it back most is interior depth, at 47 out of 100: deepest interior point 61 ft from a facade, scored from 80 ft down to 40 ft.

Built in 1987

Boston records this building as going up in 1987, 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 495,092 sq ft of converted floor, or $178.2M in total — about $458K for each of the 389 homes.

That cost is charged across every converted square foot, including the 129,654 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 $442K a home, which for 389 homes is $171.7M.

What would have to be true

A $6.5M gap before any grant, which the modeled $10.0M closes. What would reopen it soonest: circulation efficiency 2% down.

The shortfall before any grant is $6.5M. Closing it from the value side means each of the 389 homes finishing at $458K rather than the $442K the model assumes — 4% more. Closing it from the cost side means getting all-in cost down from $360 to $347 per square foot.

A modeled RESIDE grant of $10.0M moves that threshold to $432K a home. That is below the assumed value, which is why this building counts as unlocked by the grant — subject to it qualifying under the law's vacant-and-abandoned test, which this data cannot show.

Each of these, moved on its own, would be enough to undo that for 93-101 Arch St:

All four are sliders in the survey, where 93-101 Arch St re-scores against your own numbers.

How it compares in Downtown Boston

93-101 Arch St ranks 73rd of the 96 buildings screened here, against a median score of 89.

Its floor plate is better lit than 18% of them, and shallower than 26% of them at its deepest interior point. On size it is the 29th largest by estimated homes. The full survey of all 96 buildings ranks and maps every one of them, and the list by address links each to its own page.

Within the SKY zone

38th of 52 zoned SKY — the comparison that shares its rules, rents and streets.

52 of the screened buildings are zoned SKY. 93-101 Arch St ranks 38th of them against a median score of 88. 40 score 70 or more, their median deepest interior point is 51 ft from a facade against this building’s 61 ft, and together they would hold an estimated 19,019 homes. The group’s top scorer is 147 Milk St, at 100.

Its nearest match in size: 71-75 Kilby St

The screened building closest to 93-101 Arch St in converted floor area is 71-75 Kilby St: 473,005 sq ft over 13 stories, against 495,092 sq ft over 22 here.

93-101 Arch St scores 72 to its 84, and with the size held roughly equal most of that shortfall comes from daylight efficiency: 68 out of 100 here, 99 there (89% of the floor area within 35 ft of a facade, scored from 40% up to 90%). On the money they part ways: 71-75 Kilby St pencils without a subsidy, while 93-101 Arch St pencils only with the modeled RESIDE grant. The two stand about 1,300 ft apart.

Would it qualify for a RESIDE Act grant?

The model awards 93-101 Arch 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 93-101 Arch St

The 4 closest the screen also covers, from 280 ft away. They are the colored outlines on the plan at the top of this page.

• 77 Franklin St
  11 stories · 100% daylit · 77 estimated homes · scores 93/100 (Strong candidate)
  about 280 ft away
• 21-53 Summer St
  11 stories · 47% daylit · 401 estimated homes · scores 27/100 (Unlikely)
  about 320 ft away
• 40-62 Franklin St
  5 stories · 85% daylit · 47 estimated homes · scores 76/100 (Strong candidate)
  about 340 ft away
• 64-74 Franklin St
  10 stories · 91% daylit · 94 estimated homes · scores 90/100 (Strong candidate)
  about 380 ft away