77 Franklin St
77 Franklin St is a 11-story building in Downtown Boston with 100% of its floor area within daylight reach of a facade. This screen estimates 77 homes and scores it 93 out of 100 for office-to-residential conversion suitability.
MA-7 & MA-8 · Screened 2026-10-04 · Strong candidate
Where 77 Franklin St is
Its block in Downtown Boston, drawn from Boston's own building outlines and street centerlines.
- Already housing
- Not screened
- 77 Franklin St
This building's conversion pencils at default assumptions without any subsidy.
This footprint has no windowless core at all: every point on the floor plate is within 35 ft of a facade, which is unusual and is the main reason it scores as well as it does.
Modeled conversion metrics for 77 Franklin St, 2026-10-04.
| Suitability scoreStrong candidate | 93 / 100 |
|---|---|
| Storiesfrom 128 ft aerial-survey height ÷ 12 ft floor-to-floor | 11 |
| Floor plateper floor, from the city footprint | 7,307 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 100% |
| Deepest interior pointviability threshold is 80 ft | 31 ft |
| Windowless coreper floor — renovated but never rentable | 0 sq ft |
| Estimated homesat 750 sq ft average | 77 |
| Conversion cost$360/sq ft all-in on 73,070 sq ft | $26.3M |
| Gap before grantpencils unsubsidized | -$7.7M |
| Modeled RESIDE grantbelow the statutory cap | $4.6M |
| BuiltBoston publishes construction years, but none matched this footprint | — |
| ZoningDowntown Boston | SKY |
| Opportunity Zonenot in a 2018 designated tract | No |
The plan: window line, shape and floor rhythm
52 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.
The typical floor has 397 ft of exterior wall, and across 10 residential floors the building carries 3,970 ft of it in total, divided among the 77 homes this screen estimates.
Its plate is moderately compact at 0.58: 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 7.7 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 77 Franklin St scores 93 out of 100
Daylight efficiency 100, Interior depth 100, Scale 51, Finance 100 — each out of 100, then weighted.
Score components for 77 Franklin St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency100% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 100 | 45% | 45.0 |
| Interior depthdeepest interior point 31 ft from a facade, scored from 80 ft down to 40 ft | 100 | 25% | 25.0 |
| Scale77 estimated homes, scored from 0 up to 150 | 51 | 15% | 7.7 |
| Financecompleted value covers conversion cost with 47% to spare, which tops out the component | 100 | 15% | 15.0 |
Most of what it earns comes from daylight efficiency, and what holds it back most is scale, at 51 out of 100: 77 estimated homes, scored from 0 up to 150.
What the conversion would cost
$360 per square foot all-in across 73,070 sq ft of converted floor, or $26.3M in total — about $342K for each of the 77 homes.
All-in cost per square foot for 77 Franklin 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 circulation and service area that earns nothing directly. Against it the model sets a completed value of $442K a home, which for 77 homes is $34.0M.
What would have to be true
This one already clears the bar. The question is how much room it has before it stops.
At $442K a home, completed value covers the $26.3M of work with $7.7M to spare. Value per home would have to fall to $342K — 23% below the assumption — before the conversion stopped penciling, or all-in cost would have to rise from $360 to $465 per square foot. Neither is a wide margin in a market that moves, but this building does not need a grant to work.
Each of these, moved on its own, would be enough to undo that for 77 Franklin St:
Single-assumption flip points for 77 Franklin St, each holding the other three at their defaults.
| Circulation efficiencythe binding constraint — the least this building would need | 32% downto 54% |
|---|---|
| Completed value per home | 36% downto $282K |
| Average unit size | 47% upto 1,103 sq ft |
| Conversion cost per square foot | 65% upto $428/sq ft |
All four are sliders in the survey, where 77 Franklin St re-scores against your own numbers.
How it compares in Downtown Boston
77 Franklin St ranks 22nd of the 96 buildings screened here, against a median score of 89.
Its floor plate is better lit than 100% of them, and shallower than 90% of them at its deepest interior point. On size it is the 75th 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
11th of 52 zoned SKY — the comparison that shares its rules, rents and streets.
52 of the screened buildings are zoned SKY. 77 Franklin St ranks 11th 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 31 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: 103-111 Devonshire St
The screened building closest to 77 Franklin St in converted floor area is 103-111 Devonshire St: 71,951 sq ft over 11 stories, against 73,070 sq ft over 11 here.
The two land within a few points of each other — 93 here, 93 there — so at this size the screen reads them as much the same prospect. On the money they sit in the same place: each pencils without a subsidy. The two stand about 800 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 77 Franklin St $4.6M, 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 77 Franklin St
The 4 closest the screen also covers, from 110 ft away. They are the colored outlines on the plan at the top of this page.
- 20 Winthrop Sq6 stories · 100% daylit · 36 estimated homes · scores 89/100 (Strong candidate)about 110 ft away
- 64-74 Franklin St10 stories · 91% daylit · 94 estimated homes · scores 90/100 (Strong candidate)about 220 ft away
- 40-62 Franklin St5 stories · 85% daylit · 47 estimated homes · scores 76/100 (Strong candidate)about 260 ft away
- 93-101 Arch St22 stories · 74% daylit · 389 estimated homes · scores 72/100 (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.