390-400R Atlantic Ave
390-400R Atlantic Ave is a 7-story building in Downtown Boston with 79% of its floor area within daylight reach of a facade. This screen estimates 85 homes and scores it 71 out of 100 for office-to-residential conversion suitability.
MA-7 & MA-8 · Screened 2026-10-04 · Strong candidate
Where 390-400R Atlantic Ave is
Its block in Downtown Boston, drawn from Boston's own building outlines and street centerlines.
- Already housing
- Not screened
- 390-400R Atlantic Ave
This building's conversion pencils at default assumptions without any subsidy.
Every floor carries 3,493 sq ft of windowless core — area that must be gutted, re-plumbed and sprinklered but can never be rented as an apartment. Across 6 residential floors that is 20,958 sq ft of cost carrying no revenue.
Modeled conversion metrics for 390-400R Atlantic Ave, 2026-10-04.
| Suitability scoreStrong candidate | 71 / 100 |
|---|---|
| Storiesfrom 79 ft aerial-survey height ÷ 12 ft floor-to-floor | 7 |
| Floor plateper floor, from the city footprint | 16,823 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 79% |
| Deepest interior pointviability threshold is 80 ft | 60 ft |
| Windowless coreper floor — renovated but never rentable | 3,493 sq ft |
| Estimated homesat 750 sq ft average | 85 |
| Conversion cost$360/sq ft all-in on 100,939 sq ft | $36.3M |
| Gap before grantpencils unsubsidized | -$1.2M |
| Modeled RESIDE grantbelow the statutory cap | $5.1M |
| BuiltBoston's own record of the construction year | 1899 |
| ZoningDowntown Boston | DOWNTOWN WATERFRONT SUBDISTRICT |
| Opportunity Zonenot in a 2018 designated tract | No |
The plan: window line, shape and floor rhythm
37 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.
The typical floor has 521 ft of exterior wall, and across 6 residential floors the building carries 3,128 ft of it in total, divided among the 85 homes this screen estimates.
Its plate is compact at 0.78: 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 14.2 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 390-400R Atlantic Ave scores 71 out of 100
Daylight efficiency 78, Interior depth 49, Scale 57, Finance 100 — each out of 100, then weighted.
Score components for 390-400R Atlantic Ave. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency79% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 78 | 45% | 35.3 |
| Interior depthdeepest interior point 60 ft from a facade, scored from 80 ft down to 40 ft | 49 | 25% | 12.3 |
| Scale85 estimated homes, scored from 0 up to 150 | 57 | 15% | 8.5 |
| Financecompleted value covers conversion cost with 17% 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 49 out of 100: deepest interior point 60 ft from a facade, scored from 80 ft down to 40 ft.
Built in 1899
Boston records this building as going up in 1899, 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 79% daylight figure above deserves.
What the conversion would cost
$360 per square foot all-in across 100,939 sq ft of converted floor, or $36.3M in total — about $428K for each of the 85 homes.
All-in cost per square foot for 390-400R Atlantic Ave: 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 20,958 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 85 homes is $37.5M.
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 $36.3M of work with $1.2M to spare. Value per home would have to fall to $428K — 3% below the assumption — before the conversion stopped penciling, or all-in cost would have to rise from $360 to $372 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 390-400R Atlantic Ave:
Single-assumption flip points for 390-400R Atlantic Ave, each holding the other three at their defaults.
| Circulation efficiencythe binding constraint — the least this building would need | 14% downto 68% |
|---|---|
| Completed value per home | 17% downto $368K |
| Average unit size | 17% upto 877 sq ft |
| Conversion cost per square foot | 24% upto $322/sq ft |
All four are sliders in the survey, where 390-400R Atlantic Ave re-scores against your own numbers.
How it compares in Downtown Boston
390-400R Atlantic Ave ranks 75th of the 96 buildings screened here, against a median score of 89.
Its floor plate is better lit than 29% of them, and shallower than 28% of them at its deepest interior point. On size it is the 68th 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: 25 New Chardon St
The screened building closest to 390-400R Atlantic Ave in converted floor area is 25 New Chardon St: 105,913 sq ft over 7 stories, against 100,939 sq ft over 7 here.
390-400R Atlantic Ave scores 71 to its 67, and with the size held roughly equal most of that lead comes from interior depth: 49 out of 100 here, 37 there (deepest interior point 65 ft from a facade, scored from 80 ft down to 40 ft). On the money they sit in the same place: each pencils without a subsidy. The two stand about 3,900 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 390-400R Atlantic Ave $5.1M, 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 390-400R Atlantic Ave
The 4 closest the screen also covers, from 360 ft away. They are the colored outlines on the plan at the top of this page.
- 20 Rowes Whf18 stories · 84% daylit · 643 estimated homes · scores 86/100 (Strong candidate)about 360 ft away
- 40 Rowes Whf9 stories · 96% daylit · excluded: residential records on a shared parcelabout 460 ft away
- 150 Oliver St50 stories · 80% daylit · 986 estimated homes · scores 70/100 (Worth a feasibility study)about 490 ft away
- 90 Oliver St45 stories · 76% daylit · 743 estimated homes · scores 70/100 (Strong candidate)about 540 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.