255 State St
255 State St is a 11-story building in Downtown Boston with 74% of its floor area within daylight reach of a facade. This screen estimates 162 homes and scores it 68 out of 100 for office-to-residential conversion suitability.
MA-7 & MA-8 · Screened 2026-10-04 · Worth a feasibility study
Where 255 State St is
Its block in Downtown Boston, drawn from Boston's own building outlines and street centerlines.
- Already housing
- Not screened
- 255 State St
This building does not pencil on its own, but a modeled RESIDE Act grant would close the gap if the building qualified for one.
Every floor carries 5,397 sq ft of windowless core — area that must be gutted, re-plumbed and sprinklered but can never be rented as an apartment. Across 10 residential floors that is 53,967 sq ft of cost carrying no revenue.
Modeled conversion metrics for 255 State St, 2026-10-04.
| Suitability scoreWorth a feasibility study | 68 / 100 |
|---|---|
| Storiesfrom 129 ft aerial-survey height ÷ 12 ft floor-to-floor | 11 |
| Floor plateper floor, from the city footprint | 20,664 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 74% |
| Deepest interior pointviability threshold is 80 ft | 68 ft |
| Windowless coreper floor — renovated but never rentable | 5,397 sq ft |
| Estimated homesat 750 sq ft average | 162 |
| Conversion cost$360/sq ft all-in on 206,638 sq ft | $74.4M |
| Gap before grantshortfall against completed value | $2.9M |
| Modeled RESIDE grantbelow the statutory cap | $9.7M |
| BuiltBoston's own record of the construction year | 1916 |
| ZoningDowntown Boston | DOWNTOWN WATERFRONT SUBDISTRICT |
| Opportunity Zonenot in a 2018 designated tract | No |
The plan: window line, shape and floor rhythm
35 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.
The typical floor has 570 ft of exterior wall, and across 10 residential floors the building carries 5,702 ft of it in total, divided among the 162 homes this screen estimates.
Its plate is compact at 0.80: 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 16.2 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 255 State St scores 68 out of 100
Daylight efficiency 68, Interior depth 31, Scale 100, Finance 100 — each out of 100, then weighted.
Score components for 255 State St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency74% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 68 | 45% | 30.5 |
| Interior depthdeepest interior point 68 ft from a facade, scored from 80 ft down to 40 ft | 31 | 25% | 7.8 |
| Scale162 estimated homes, scored from 0 up to 150 | 100 | 15% | 15.0 |
| Financecompleted value covers conversion cost with 9% 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 31 out of 100: deepest interior point 68 ft from a facade, scored from 80 ft down to 40 ft.
Built in 1916
Boston records this building as going up in 1916, 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 74% daylight figure above deserves.
What the conversion would cost
$360 per square foot all-in across 206,638 sq ft of converted floor, or $74.4M in total — about $459K for each of the 162 homes.
All-in cost per square foot for 255 State 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 53,967 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 162 homes is $71.5M.
What would have to be true
A $2.9M gap before any grant, which the modeled $9.7M closes. What would reopen it soonest: circulation efficiency 9% down.
The shortfall before any grant is $2.9M. Closing it from the value side means each of the 162 homes finishing at $459K rather than the $442K the model assumes — 4% more. Closing it from the cost side means getting all-in cost down from $360 to $346 per square foot.
A modeled RESIDE grant of $9.7M moves that threshold to $399K 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 255 State St:
Single-assumption flip points for 255 State St, each holding the other three at their defaults.
| Circulation efficiencythe binding constraint — the least this building would need | 9% downto 73% |
|---|---|
| Average unit size | 9% upto 820 sq ft |
| Completed value per home | 10% downto $399K |
| Conversion cost per square foot | 13% upto $293/sq ft |
All four are sliders in the survey, where 255 State St re-scores against your own numbers.
How it compares in Downtown Boston
255 State St ranks 79th of the 96 buildings screened here, against a median score of 89.
Its floor plate is better lit than 19% of them, and shallower than 18% of them at its deepest interior point. On size it is the 48th 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.
Its nearest match in size: 22-40 Chauncy St
The screened building closest to 255 State St in converted floor area is 22-40 Chauncy St: 213,376 sq ft over 11 stories, against 206,638 sq ft over 11 here.
255 State St scores 68 to its 88, and with the size held roughly equal most of that shortfall comes from daylight efficiency: 68 out of 100 here, 92 there (86% of the floor area within 35 ft of a facade, scored from 40% up to 90%). On the money they part ways: 22-40 Chauncy St pencils without a subsidy, while 255 State St pencils only with the modeled RESIDE grant. The two stand about 3,100 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 255 State St $9.7M, 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 255 State St
The 4 closest the screen also covers, from 490 ft away. They are the colored outlines on the plan at the top of this page.
- 177 Milk St10 stories · 90% daylit · 96 estimated homes · scores 89/100 (Strong candidate)about 490 ft away
- 200 State St18 stories · 80% daylit · 547 estimated homes · scores 75/100 (Strong candidate)about 560 ft away
- 21 Custom House St9 stories · 92% daylit · 82 estimated homes · scores 91/100 (Strong candidate)about 620 ft away
- 150-152 State St8 stories · 100% daylit · 131 estimated homes · scores 98/100 (Strong candidate)about 730 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.