621 17th St
621 17th St is a 36-story building in Greater Downtown Denver with 84% of its floor area within daylight reach of a facade. This screen estimates 1,169 homes and scores it 84 out of 100 for office-to-residential conversion suitability.
CO-1 · Screened 2026-09-19 · Strong candidate
Also addressed as 633 17th St and 1722 California St: Denver’s address records place all 3 on this one footprint.
Where 621 17th St is
Its block in Greater Downtown Denver, drawn from Denver's own building outlines and street centerlines.
- Already housing
- Not screened
- 621 17th St
This building does not pencil at default assumptions, even with a modeled RESIDE Act grant.
Across its 35 residential floors this building carries 213,802 sq ft of windowless core — area that must be gutted, re-plumbed and sprinklered but can never be rented as an apartment.
Modeled conversion metrics for 621 17th St, 2026-09-19.
| Suitability scoreStrong candidate | 84 / 100 |
|---|---|
| Storiesfrom 436 ft aerial-survey height ÷ 12 ft floor-to-floor | 36 |
| Height bandsfloor plate by floor range, from the city's roof outlines | Floors 1–4: 84,778 sq ft · Floor 5: 81,427 sq ft · Floor 6: 70,339 sq ft · Floors 7–8: 39,668 sq ft · Floors 9–31: 32,167 sq ft · Floors 32–35: 20,016 sq ft · Floor 36: 4,854 sq ft |
| Floor platetypical floor, from the city outlines | 32,167 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 84% |
| Deepest interior pointviability threshold is 80 ft | 41 ft |
| Windowless coretypical floor; the building-wide total is in the text above | 2,858 sq ft |
| Estimated homesat 750 sq ft average | 1,169 |
| Conversion cost$360/sq ft all-in on 1,310,204 sq ft | $471.7M |
| Gap before grantshortfall against completed value | $195.8M |
| Modeled RESIDE grantat the statutory per-award cap | $10.0M |
| BuiltDenver does not publish a construction year with this data | — |
| ZoningCBD | D-C |
| 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 1,222 ft of exterior wall, and across 35 residential floors the building carries 43,647 ft of it in total, divided among the 1,169 homes this screen estimates.
Its plate is elongated at 0.27: a slab or an L, which is why so much of the floor lies within reach of a window: the outline buys daylight that a square plan of the same area would not. How window line and plate shape are measured.
At the model’s 750 sq ft average, the plan works out at about 33.4 homes per floor. Its floors are not alike, though: the typical floor's deepest interior point is 41 ft from a facade, while its worst floor reaches 80 ft. The score follows the typical floor, so a podium that could not hold a bedroom does not by itself sink a slim tower above it — but it is there, and it is part of what would have to be drawn around.
Why 621 17th St scores 84 out of 100
Daylight efficiency 87, Interior depth 98, Scale 100, Finance 34 — each out of 100, then weighted.
Score components for 621 17th St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency84% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 87 | 45% | 39.3 |
| Interior depthdeepest interior point 41 ft from a facade, scored from 80 ft down to 40 ft | 98 | 25% | 24.5 |
| Scale1169 estimated homes, scored from 0 up to 150 | 100 | 15% | 15.0 |
| Financeremaining gap is 39% of conversion cost, scored from 60% down to 0% | 34 | 15% | 5.2 |
Most of what it earns comes from daylight efficiency, and what holds it back most is finance, at 34 out of 100: remaining gap is 39% of conversion cost, scored from 60% down to 0%.
What the conversion would cost
$360 per square foot all-in across 1,310,204 sq ft of converted floor, or $471.7M in total — about $403K for each of the 1,169 homes.
All-in cost per square foot for 621 17th 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 213,802 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 $236K a home, which for 1,169 homes is $275.9M.
What would have to be true
A $195.8M gap before any grant, $185.8M after the modeled one. The smallest single change that would close it: average unit size 40% down.
The shortfall before any grant is $195.8M. Closing it from the value side means each of the 1,169 homes finishing at $403K rather than the $236K the model assumes — 71% more. Closing it from the cost side means getting all-in cost down from $360 to $211 per square foot.
A modeled RESIDE grant of $10.0M moves that threshold to $395K a home. That is still above the $236K assumed, leaving $185.8M uncovered, which is why the grant does not unlock this one.
Nor do all four levers have to move. For 621 17th St, one alone would close the gap at:
Single-assumption flip points for 621 17th St, each holding the other three at their defaults.
| Average unit sizethe binding constraint — the least this building would need | 40% downto 448 sq ft |
|---|---|
| Conversion cost per square foot | 55% downto $118/sq ft |
| Completed value per home | 67% upto $395K |
All four are sliders in the survey, where 621 17th St re-scores against your own numbers.
How it compares in Greater Downtown Denver
621 17th St ranks 61st of the 214 buildings screened here, against a median score of 72.
Its floor plate is better lit than 52% of them, and shallower than 83% of them at its deepest interior point. On size it is the 8th largest by estimated homes. The full survey of all 214 buildings ranks and maps every one of them, and the list by address links each to its own page.
Within CBD and the D-C zone
19th of 75 in CBD, 17th of 72 zoned D-C — the comparison that shares its rules, rents and streets.
Denver places 75 of the screened buildings in CBD. 621 17th St ranks 19th of them against a median score of 71. 40 score 70 or more, their median deepest interior point is 56 ft from a facade against this building’s 41 ft, and together they would hold an estimated 33,698 homes. The group’s top scorer is 918 17th St, at 97.
72 of the screened buildings are zoned D-C. 621 17th St ranks 17th of them against a median score of 73. 39 score 70 or more, their median deepest interior point is 57 ft from a facade against this building’s 41 ft, and together they would hold an estimated 32,881 homes. The group’s top scorer is 721 19th St, at 95.
Its nearest match in size: 1125 17th St
The screened building closest to 621 17th St in converted floor area is 1125 17th St: 1,439,750 sq ft over 37 stories, against 1,310,204 sq ft over 36 here.
621 17th St scores 84 to its 62, and with the size held roughly equal most of that lead comes from interior depth: 98 out of 100 here, 48 there (deepest interior point 61 ft from a facade, scored from 80 ft down to 40 ft). On the money they sit in the same place: each falls short even with the modeled grant. The two stand about 1,900 ft apart.
The city's own study picked this building too
In August 2023 Denver and the architecture firm Gensler rated 21 downtown office buildings good candidates for conversion to housing and published the top 16 by address. One of them resolves to this building: “621 17th St”.
That is an outside opinion reached by different means — architects reading plans, not a model reading outlines — and this screen agrees with it: 621 17th St scores 84 out of 100 here, in the same top tier. The difference is the money rather than the geometry: at default assumptions the gap here is $195.8M, which no modeled RESIDE grant closes. A study asking whether a building can be converted and a model asking whether it would pencil are answering different questions.
Mile High CRE, Study Identifies 21 Downtown Denver Office Buildings as Good Candidates for Conversion. The full comparison across all 16 is on the Greater Downtown Denver page.
Would it qualify for a RESIDE Act grant?
The model awards 621 17th 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 621 17th St
The 4 closest the screen also covers, from 330 ft away. They are the colored outlines on the plan at the top of this page.
- 515 17th St42 stories · 77% daylit · 1,110 estimated homes · scores 65/100 (Worth a feasibility study)about 330 ft away
- 707 17th St44 stories · 73% daylit · 822 estimated homes · scores 62/100 (Worth a feasibility study)about 380 ft away
- 600 17th St34 stories · 82% daylit · 651 estimated homes · scores 73/100 (Strong candidate)about 440 ft away
- 717 17th St33 stories · 73% daylit · 593 estimated homes · scores 61/100 (Worth a feasibility study)about 450 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.