675 15th St

675 15th St is a 38-story building in Greater Downtown Denver with 58% of its floor area within daylight reach of a facade. This screen estimates 1,009 homes and scores it 32 out of 100 for office-to-residential conversion suitability.

CO-1 · Screened 2026-09-19 · Marginal

Build a conversion planCheck its numbers, lay out its homes and get a two-page PDF. Free.

Also addressed as 1514 California St, 1518 California St, 1520 California St, 1522 California St, 1515 Welton St and 1525 Welton St: Denver’s address records place all 7 on this one footprint.

Where 675 15th St is

Its block in Greater Downtown Denver, drawn from Denver's own building outlines and street centerlines.

Suitability score

0–29

30–49

50–69

70–100

Already housing
Not screened
675 15th St

675 15th St and the 1,000 ft of Greater Downtown Denver around it. The streets are drawn at the width of the right-of-way they run down, sidewalks included, and named, and every building on these blocks is drawn. What is left open and stippled is neither: a surface lot, a plaza or a vacant parcel. The screened buildings are colored by the ramp above, the same one the district map uses, carry their score, and each is a link to its own page. Each casts a shadow as long as its measured height lets it, so towers stand out from the low buildings around them; the unscreened buildings have no measured height and cast none. 675 15th St is outlined in its own score color at the outline it covers at ground level. Dashed inside it is the typical floor, the one the floor-plate figure below draws, because this building steps back as it rises. Its windowless core is hatched. The inset places it among every building the screen covers.

Typical floor plan: 58% of the building’s floor area sits within daylight reach of a facade; the drawing shows its typical floor, where the share is 57%. The shading is daylight, darkest at the windows and gone 35 ft in. The hatched area is windowless core: 18,758 sq ft per typical floor that must be renovated but can never be rented as an apartment. The dimension marks the deepest interior point, 86 ft from the nearest window. A–A is where the section beside it is cut.

Section A–A: cut across the depth of the plate, through the middle of the core. Daylight reaches 35 ft in from every facade, fading as it goes, and the hatched stripe left between the lit edges is floor that gets converted and can never be rented: 18,758 sq ft on the floor the screen scores, and 677,261 sq ft over 37 residential floors. The steps are where the building sets back as it rises. The shaded ground floor is converted like the rest and counted as no homes.

This building does not pencil at default assumptions, even with a modeled RESIDE Act grant.

Across its 37 residential floors this building carries 677,261 sq ft of windowless core — area that must be gutted, re-plumbed and sprinklered but can never be rented as an apartment.

Read with caution. This footprint carries 7 street addresses across 44,113 sq ft, which usually means the city’s GIS has merged a block or complex into a single polygon rather than describing one convertible building.

Modeled conversion metrics for 675 15th St, 2026-09-19.

Suitability scoreMarginal	32 / 100
Storiesfrom 454 ft aerial-survey height ÷ 12 ft floor-to-floor	38
Height bandsfloor plate by floor range, from the city's roof outlines	Floors 1–37: 44,113 sq ft · Floor 38: 35,462 sq ft
Floor platetypical floor, from the city outlines	44,113 sq ft
Daylight efficiencyshare within 35 ft of a facade	58%
Deepest interior pointviability threshold is 80 ft	86 ft
Windowless coretypical floor; the building-wide total is in the text above	18,758 sq ft
Estimated homesat 750 sq ft average	1,009
Conversion cost$360/sq ft all-in on 1,623,523 sq ft	$584.5M
Gap before grantshortfall against completed value	$346.3M
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

34 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.

The typical floor has 918 ft of exterior wall, and across 37 residential floors the building carries 34,392 ft of it in total, divided among the 1,009 homes this screen estimates.

Its plate is moderately compact at 0.66: a squarish plan, with enough perimeter for a conventional double-loaded corridor. How window line and plate shape are measured.

At the model’s 750 sq ft average, the plan works out at about 27.3 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.

Why 675 15th St scores 32 out of 100

Daylight efficiency 37, Interior depth 0, Scale 100, Finance 4 — each out of 100, then weighted.

Score components for 675 15th St. Points are the subscore times its weight.

Component	Subscore	Weight	Points
Daylight efficiency58% of the floor area within 35 ft of a facade, scored from 40% up to 90%	37	45%	16.5
Interior depthdeepest interior point 86 ft from a facade, scored from 80 ft down to 40 ft	0	25%	0.0
Scale1009 estimated homes, scored from 0 up to 150	100	15%	15.0
Financeremaining gap is 58% of conversion cost, scored from 60% down to 0%	4	15%	0.6

Most of what it earns comes from daylight efficiency, and what holds it back most is interior depth, at 0 out of 100: deepest interior point 86 ft from a facade, scored from 80 ft down to 40 ft.

What the conversion would cost

$360 per square foot all-in across 1,623,523 sq ft of converted floor, or $584.5M in total — about $579K for each of the 1,009 homes.

All-in cost per square foot for 675 15th 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 677,261 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 1,009 homes is $238.1M.

What would have to be true

A $346.3M gap before any grant, $336.3M after the modeled one. The smallest single change that would close it: average unit size 59% down.

The shortfall before any grant is $346.3M. Closing it from the value side means each of the 1,009 homes finishing at $579K rather than the $236K the model assumes — 145% more. Closing it from the cost side means getting all-in cost down from $360 to $147 per square foot.

A modeled RESIDE grant of $10.0M moves that threshold to $569K a home. That is still above the $236K assumed, leaving $336.3M uncovered, which is why the grant does not unlock this one.

Nor do all four levers have to move. For 675 15th St, one alone would close the gap at:

Single-assumption flip points for 675 15th St, each holding the other three at their defaults.

Average unit sizethe binding constraint — the least this building would need	59% downto 311 sq ft
Conversion cost per square foot	80% downto $53/sq ft
Completed value per home	141% upto $569K

All four are sliders in the survey, where 675 15th St re-scores against your own numbers.

How it compares in Greater Downtown Denver

675 15th St ranks 210th of the 214 buildings screened here, against a median score of 72.

Its floor plate is better lit than 3% of them, and shallower than 4% of them at its deepest interior point. On size it is the 12th 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

73rd of 75 in CBD, 72nd of 72 zoned D-C — the comparison that shares its rules, rents and streets.

Denver places 75 of the screened buildings in CBD. 675 15th St ranks 73rd 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 86 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. 675 15th St ranks 72nd 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 86 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: 999 18th St

The screened building closest to 675 15th St in converted floor area is 999 18th St: 1,591,416 sq ft over 36 stories, against 1,623,523 sq ft over 38 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 675 15th 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 675 15th St

The 4 closest the screen also covers, from 270 ft away. They are the colored outlines on the plan at the top of this page.

600 16th St
6 stories · 87% daylit · 51 estimated homes · scores 74/100 (Strong candidate)
about 270 ft away
707 15th St
11 stories · 65% daylit · already an apartment building
about 300 ft away
650 15th St
37 stories · 71% daylit · 814 estimated homes · scores 71/100 (Strong candidate)
about 380 ft away
550 15th St
17 stories · 78% daylit · 253 estimated homes · scores 70/100 (Worth a feasibility study)
about 380 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.