43-45 Devonshire St
43-45 Devonshire St is a 13-story building in Downtown Boston with 96% of its floor area within daylight reach of a facade. This screen estimates 111 homes and scores it 96 out of 100 for office-to-residential conversion suitability.
MA-7 & MA-8 · Screened 2026-10-04 · Strong candidate
Also addressed as 1-1A State St: Boston’s address records place both on this one footprint.
Where 43-45 Devonshire St is
Its block in Downtown Boston, drawn from Boston's own building outlines and street centerlines.
- Already housing
- Not screened
- 43-45 Devonshire St
This building's conversion pencils at default assumptions without any subsidy.
Every floor carries 409 sq ft of windowless core — area that must be gutted, re-plumbed and sprinklered but can never be rented as an apartment. Across 12 residential floors that is 4,903 sq ft of cost carrying no revenue.
Modeled conversion metrics for 43-45 Devonshire St, 2026-10-04.
| Suitability scoreStrong candidate | 96 / 100 |
|---|---|
| Storiesfrom 156 ft aerial-survey height ÷ 12 ft floor-to-floor | 13 |
| Floor plateper floor, from the city footprint | 9,140 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 96% |
| Deepest interior pointviability threshold is 80 ft | 40 ft |
| Windowless coreper floor — renovated but never rentable | 409 sq ft |
| Estimated homesat 750 sq ft average | 111 |
| Conversion cost$360/sq ft all-in on 109,677 sq ft | $39.5M |
| Gap before grantpencils unsubsidized | -$9.5M |
| Modeled RESIDE grantbelow the statutory cap | $6.7M |
| BuiltBoston's own record of the construction year | 1920 |
| ZoningDowntown Boston | SKY |
| Opportunity Zonenot in a 2018 designated tract | No |
The plan: window line, shape and floor rhythm
43 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.
The typical floor has 395 ft of exterior wall, and across 12 residential floors the building carries 4,744 ft of it in total, divided among the 111 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 9.3 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 43-45 Devonshire St scores 96 out of 100
Daylight efficiency 100, Interior depth 99, Scale 74, Finance 100 — each out of 100, then weighted.
Score components for 43-45 Devonshire St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency96% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 100 | 45% | 45.0 |
| Interior depthdeepest interior point 40 ft from a facade, scored from 80 ft down to 40 ft | 99 | 25% | 24.7 |
| Scale111 estimated homes, scored from 0 up to 150 | 74 | 15% | 11.1 |
| Financecompleted value covers conversion cost with 41% 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 74 out of 100: 111 estimated homes, scored from 0 up to 150.
Built in 1920
Boston records this building as going up in 1920, which puts it in the interwar stock.
As a rule, steel or concrete frames with punched windows and plates still narrow enough for daylight to reach the middle, often with high ceilings. Among the most convertible stock there is, and the reason so many early conversions were of buildings this age. 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 96% daylight figure above deserves.
What the conversion would cost
$360 per square foot all-in across 109,677 sq ft of converted floor, or $39.5M in total — about $356K for each of the 111 homes.
All-in cost per square foot for 43-45 Devonshire 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 4,903 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 111 homes is $49.0M.
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 $39.5M of work with $9.5M to spare. Value per home would have to fall to $356K — 19% below the assumption — before the conversion stopped penciling, or all-in cost would have to rise from $360 to $447 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 43-45 Devonshire St:
Single-assumption flip points for 43-45 Devonshire St, each holding the other three at their defaults.
| Circulation efficiencythe binding constraint — the least this building would need | 29% downto 57% |
|---|---|
| Completed value per home | 33% downto $296K |
| Average unit size | 41% upto 1,061 sq ft |
| Conversion cost per square foot | 57% upto $408/sq ft |
All four are sliders in the survey, where 43-45 Devonshire St re-scores against your own numbers.
How it compares in Downtown Boston
43-45 Devonshire St ranks 12th of the 96 buildings screened here, against a median score of 89.
Its floor plate is better lit than 65% of them, and shallower than 68% of them at its deepest interior point. On size it is the 61st 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
6th of 52 zoned SKY — the comparison that shares its rules, rents and streets.
52 of the screened buildings are zoned SKY. 43-45 Devonshire St ranks 6th 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 40 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: 28-38 Winter St
The screened building closest to 43-45 Devonshire St in converted floor area is 28-38 Winter St: 105,001 sq ft over 14 stories, against 109,677 sq ft over 13 here.
The two land within a few points of each other — 96 here, 95 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 1,500 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 43-45 Devonshire St $6.7M, 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 43-45 Devonshire St
The 4 closest the screen also covers, from 300 ft away. They are the colored outlines on the plan at the top of this page.
- 1-11 Court St16 stories · 85% daylit · 233 estimated homes · scores 90/100 (Strong candidate)about 300 ft away
- 15 Court Sq11 stories · 100% daylit · 81 estimated homes · scores 93/100 (Strong candidate)about 310 ft away
- 28 State St42 stories · 83% daylit · 621 estimated homes · scores 88/100 (Strong candidate)about 320 ft away
- 276-278 Washington St9 stories · 100% daylit · 55 estimated homes · scores 91/100 (Strong candidate)about 350 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.