999 18th St
999 18th St is a 36-story building in Greater Downtown Denver with 88% of its floor area within daylight reach of a facade. This screen estimates 1,485 homes and scores it 81 out of 100 for office-to-residential conversion suitability.
CO-1 · Screened 2026-09-19 · Strong candidate
Also addressed as 1849 Curtis St, 1871 Curtis St, 1881 Curtis St and 1891 Curtis St: Denver’s address records place all 5 on this one footprint.
Where 999 18th St is
Its block in Greater Downtown Denver, drawn from Denver's own building outlines and street centerlines.
- Already housing
- Not screened
- 999 18th St
This building does not pencil at default assumptions, even with a modeled RESIDE Act grant.
Across its 35 residential floors this building carries 198,417 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 999 18th St, 2026-09-19.
| Suitability scoreStrong candidate | 81 / 100 |
|---|---|
| Storiesfrom 435 ft aerial-survey height ÷ 12 ft floor-to-floor | 36 |
| Height bandsfloor plate by floor range, from the city's roof outlines | Floors 1–2: 142,307 sq ft · Floor 3: 137,588 sq ft · Floor 4: 101,230 sq ft · Floors 5–6: 82,108 sq ft · Floors 7–8: 62,281 sq ft · Floor 9: 50,107 sq ft · Floors 10–25: 37,944 sq ft · Floor 26: 26,580 sq ft · Floors 27–35: 24,881 sq ft · Floor 36: 13,785 sq ft |
| Floor platetypical floor, from the city outlines | 37,944 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 88% |
| Deepest interior pointviability threshold is 80 ft | 53 ft |
| Windowless coretypical floor; the building-wide total is in the text above | 3,556 sq ft |
| Estimated homesat 750 sq ft average | 1,485 |
| Conversion cost$360/sq ft all-in on 1,591,416 sq ft | $572.9M |
| Gap before grantshortfall against completed value | $222.4M |
| 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 1,408 ft of exterior wall, and across 35 residential floors the building carries 54,546 ft of it in total, divided among the 1,485 homes this screen estimates.
Its plate is highly articulated at 0.24: a long, notched or wing-shaped outline with far more facade than its area needs — wasteful as an office envelope, and close to ideal for apartments. How window line and plate shape are measured.
At the model’s 750 sq ft average, the plan works out at about 42.4 homes per floor. Its floors are not alike, though: the typical floor's deepest interior point is 53 ft from a facade, while its worst floor reaches 96 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 999 18th St scores 81 out of 100
Daylight efficiency 95, Interior depth 69, Scale 100, Finance 38 — each out of 100, then weighted.
Score components for 999 18th St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency88% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 95 | 45% | 42.8 |
| Interior depthdeepest interior point 53 ft from a facade, scored from 80 ft down to 40 ft | 69 | 25% | 17.2 |
| Scale1485 estimated homes, scored from 0 up to 150 | 100 | 15% | 15.0 |
| Financeremaining gap is 37% of conversion cost, scored from 60% down to 0% | 38 | 15% | 5.7 |
Most of what it earns comes from daylight efficiency, and what holds it back most is finance, at 38 out of 100: remaining gap is 37% of conversion cost, scored from 60% down to 0%.
What the conversion would cost
$360 per square foot all-in across 1,591,416 sq ft of converted floor, or $572.9M in total — about $386K for each of the 1,485 homes.
All-in cost per square foot for 999 18th 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 198,417 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 1,485 homes is $350.5M.
What would have to be true
A $222.4M gap before any grant, $212.4M after the modeled one. The smallest single change that would close it: average unit size 38% down.
The shortfall before any grant is $222.4M. Closing it from the value side means each of the 1,485 homes finishing at $386K rather than the $236K the model assumes — 63% more. Closing it from the cost side means getting all-in cost down from $360 to $220 per square foot.
A modeled RESIDE grant of $10.0M moves that threshold to $379K a home. That is still above the $236K assumed, leaving $212.4M uncovered, which is why the grant does not unlock this one.
Nor do all four levers have to move. For 999 18th St, one alone would close the gap at:
Single-assumption flip points for 999 18th St, each holding the other three at their defaults.
| Average unit sizethe binding constraint — the least this building would need | 38% downto 467 sq ft |
|---|---|
| Conversion cost per square foot | 51% downto $127/sq ft |
| Completed value per home | 61% upto $379K |
All four are sliders in the survey, where 999 18th St re-scores against your own numbers.
How it compares in Greater Downtown Denver
999 18th St ranks 74th of the 214 buildings screened here, against a median score of 72.
Its floor plate is better lit than 64% of them, and shallower than 59% of them at its deepest interior point. On size it is the 3rd 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
24th of 75 in CBD, 23rd of 72 zoned D-C — the comparison that shares its rules, rents and streets.
Denver places 75 of the screened buildings in CBD. 999 18th St ranks 24th 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 53 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. 999 18th St ranks 23rd 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 53 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: 675 15th St
The screened building closest to 999 18th St in converted floor area is 675 15th St: 1,623,523 sq ft over 38 stories, against 1,591,416 sq ft over 36 here.
999 18th St scores 81 and 675 15th St only 32, and the difference is a hard fail rather than a matter of degree: the lower one is capped at 35 because its deepest interior point is 86 ft from a facade, past the 80 ft threshold beyond which conversion requires carving a light well. On the money they sit in the same place: each falls short even with the modeled grant. The two stand about 2,000 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 999 18th 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 999 18th St
The 4 closest the screen also covers, from 280 ft away. They are the colored outlines on the plan at the top of this page.
- 1099 18th St36 stories · 78% daylit · 589 estimated homes · scores 66/100 (Worth a feasibility study)about 280 ft away
- 901 19th St21 stories · 82% daylit · 377 estimated homes · scores 69/100 (Worth a feasibility study)about 410 ft away
- 1823 Stout St8 stories · 76% daylit · 269 estimated homes · scores 78/100 (Strong candidate)about 450 ft away
- 1801 Arapahoe St11 stories · 100% daylit · already an apartment buildingabout 490 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.