260 Franklin St
260 Franklin St is a 26-story building in Downtown Boston with 81% of its floor area within daylight reach of a facade. This screen estimates 358 homes and scores it 84 out of 100 for office-to-residential conversion suitability.
MA-7 & MA-8 · Screened 2026-10-04 · Strong candidate
Where 260 Franklin St is
Its block in Downtown Boston, drawn from Boston's own building outlines and street centerlines.
- Already housing
- Not screened
- 260 Franklin St
This building's conversion pencils at default assumptions without any subsidy.
Every floor carries 3,057 sq ft of windowless core — area that must be gutted, re-plumbed and sprinklered but can never be rented as an apartment. Across 25 residential floors that is 76,418 sq ft of cost carrying no revenue.
Modeled conversion metrics for 260 Franklin St, 2026-10-04.
| Suitability scoreStrong candidate | 84 / 100 |
|---|---|
| Storiesfrom 315 ft aerial-survey height ÷ 12 ft floor-to-floor | 26 |
| Floor plateper floor, from the city footprint | 16,484 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 81% |
| Deepest interior pointviability threshold is 80 ft | 53 ft |
| Windowless coreper floor — renovated but never rentable | 3,057 sq ft |
| Estimated homesat 750 sq ft average | 358 |
| Conversion cost$360/sq ft all-in on 412,095 sq ft | $148.4M |
| Gap before grantpencils unsubsidized | -$9.7M |
| Modeled RESIDE grantat the statutory per-award cap | $10.0M |
| BuiltBoston's own record of the construction year | 1983 |
| ZoningDowntown Boston | SKY |
| Opportunity Zonenot in a 2018 designated tract | No |
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 518 ft of exterior wall, and across 25 residential floors the building carries 12,960 ft of it in total, divided among the 358 homes this screen estimates.
Its plate is compact at 0.77: 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 14.3 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 260 Franklin St scores 84 out of 100
Daylight efficiency 83, Interior depth 67, Scale 100, Finance 100 — each out of 100, then weighted.
Score components for 260 Franklin St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency81% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 83 | 45% | 37.3 |
| Interior depthdeepest interior point 53 ft from a facade, scored from 80 ft down to 40 ft | 67 | 25% | 16.7 |
| Scale358 estimated homes, scored from 0 up to 150 | 100 | 15% | 15.0 |
| Financecompleted value covers conversion cost with 13% 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 interior depth, at 67 out of 100: deepest interior point 53 ft from a facade, scored from 80 ft down to 40 ft.
Built in 1983
Boston records this building as going up in 1983, 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 81% daylight figure above deserves.
What the conversion would cost
$360 per square foot all-in across 412,095 sq ft of converted floor, or $148.4M in total — about $414K for each of the 358 homes.
All-in cost per square foot for 260 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 76,418 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 358 homes is $158.1M.
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 $148.4M of work with $9.7M to spare. Value per home would have to fall to $414K — 6% below the assumption — before the conversion stopped penciling, or all-in cost would have to rise from $360 to $384 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 260 Franklin St:
Single-assumption flip points for 260 Franklin St, each holding the other three at their defaults.
| Circulation efficiencythe binding constraint — the least this building would need | 12% downto 70% |
|---|---|
| Completed value per home | 12% downto $386K |
| Average unit size | 14% upto 855 sq ft |
| Conversion cost per square foot | 18% upto $308/sq ft |
All four are sliders in the survey, where 260 Franklin St re-scores against your own numbers.
How it compares in Downtown Boston
260 Franklin St ranks 61st of the 96 buildings screened here, against a median score of 89.
Its floor plate is better lit than 32% of them, and shallower than 40% of them at its deepest interior point. On size it is the 30th 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
33rd of 52 zoned SKY — the comparison that shares its rules, rents and streets.
52 of the screened buildings are zoned SKY. 260 Franklin St ranks 33rd 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 53 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: 93-101 Arch St
The screened building closest to 260 Franklin St in converted floor area is 93-101 Arch St: 495,092 sq ft over 22 stories, against 412,095 sq ft over 26 here.
260 Franklin St scores 84 to its 72, and with the size held roughly equal most of that lead comes from daylight efficiency: 83 out of 100 here, 68 there (74% of the floor area within 35 ft of a facade, scored from 40% up to 90%). On the money they part ways: 93-101 Arch St pencils only with the modeled RESIDE grant, while 260 Franklin St pencils without a subsidy. The two stand about 1,600 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 260 Franklin 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 260 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.
- 55-61 Batterymarch St7 stories · 100% daylit · 38 estimated homes · scores 89/100 (Strong candidate)about 110 ft away
- 147 Milk St10 stories · 100% daylit · 259 estimated homes · scores 100/100 (Strong candidate)about 160 ft away
- 225 Franklin St40 stories · 75% daylit · 722 estimated homes · scores 80/100 (Strong candidate)about 330 ft away
- 1 Liberty Sq13 stories · 84% daylit · 156 estimated homes · scores 87/100 (Strong candidate)about 360 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.