"This is a small step for housing and for personal freedom and affordability. But it feels like a giant leap forward for inclusion and community."
That's Boulder city councilmember Nicole Speer, speaking in August 2023 after the council voted 6-3 to raise the city's occupancy cap from three unrelated adults to five. It was a genuinely contested vote. Two years earlier, in 2021, Boulder voters had rejected a ballot measure called Bedrooms Are For People that would have gone even further, tying occupancy to one person per bedroom plus one. The 2023 compromise felt, at the time, like the final word on a debate the city had been having since the 1960s.
It wasn't. Eight months later, the debate stopped mattering entirely, and almost nobody outside city planning noticed.
The Vote That Stopped Mattering
In April 2024, Governor Jared Polis signed HB24-1007, a state law prohibiting Colorado cities from capping residential occupancy based on how many unrelated people live together. Boulder's carefully negotiated three-to-five compromise, along with every local fight that preceded it, became legally unenforceable. The city didn't get to keep its number. The state removed the question from the table statewide.
What replaced it is the part most buyers comparing Boulder to other Boulder Valley towns haven't caught up to yet. The city didn't just stop enforcing a headcount rule and leave a vacuum. It adopted a completely different way of measuring how many people a home can legally hold, and that measurement is now a physical property of the house itself rather than a political number set by a council vote.
What Actually Governs Occupancy Now
Boulder's Ordinance 8651, adopted March 6, 2025, formally struck every reference to occupancy based on family status or unrelated-persons counts from the city's land use code. In its place, occupancy is now governed entirely by the International Property Maintenance Code, specifically section 404.4.1, which sets minimum bedroom size relative to the number of people sleeping in it. The city also enforces table 404.5, which sets minimum living and dining room area based on total occupants in the unit.
The formula is simple on paper:
| Bedroom size | Maximum occupants under IPMC 404.4.1 |
|---|---|
| 70 sq ft | 1 |
| 100 sq ft | 2 |
| 150 sq ft | 3 |
That's a meaningful shift for anyone evaluating a property as more than a place to live. Two four-bedroom Boulder houses with identical bedroom counts can have very different legal ceilings on how many people they can house, depending on whether those bedrooms measure 90 square feet or 160. The number that used to live in city code now lives in the floor plan. A buyer pulling up a listing has to look at room dimensions, not just a bedroom count, to know what a property can actually support. Individual leases can still set tighter limits than the city allows, so this is a ceiling, not a promise.
There's a quieter loss buried in the same ordinance. Boulder's cooperative housing chapter, introduced in 2017 to let larger groups live together under a licensed structure, was eliminated as part of the cleanup, since it conflicted with the new state law. Planning Board member Claudia Hanson Thiem called it bittersweet to see years of advocacy work erased even while supporting the broader change. It's a small detail, but it's the kind of thing that only shows up if you've actually read the ordinance history rather than the summary.
The ADU Half Nobody's Pricing In
The occupancy rewrite landed at almost the same moment as a second change that matters more for anyone thinking about income potential rather than roommates. Boulder's Ordinance 8650, adopted February 6, 2025 and effective that March, rewrote the rules for accessory dwelling units. The changes:
- Eliminated the requirement that an owner live in either the primary home or the ADU
- Removed the ADU parking minimum entirely
- Removed the minimum lot size requirement for building an ADU
- Dropped side-entrance screening and private open space requirements
The owner-occupancy piece is the one worth sitting with. A Boulder buyer can now purchase a house with an ADU, rent out both units, and never live in either one, as long as the property was structured that way from the start. That's a meaningfully looser stance than some neighboring markets. Denver, for comparison, still requires that at least one owner occupy the existing primary dwelling at the time an ADU permit is submitted in single-unit zones. Boulder dropped that requirement outright.
None of this makes a new Boulder ADU a short-term rental play. The city's short-term rental framework only allows it for units where both the ADU and the STR license existed before February 1, 2019. Anything built under the new rules is long-term rental math, not nightly income. There's also a real cost line buyers should budget for: detached ADUs require an automatic fire sprinkler system on a dedicated bypass meter, running roughly $8,000 to $15,000, on top of the standard build.
Not Every Lot Gets the Same Math
The zoning change is citywide, but the practical opportunity isn't evenly distributed. North Boulder, Newlands, and Gunbarrel tend to have larger lots, fewer overlay restrictions, and common alley access, which supports the full 800 square foot detached ADU envelope (or up to 1,000 square feet under the Affordable ADU path, which trades a larger footprint for a 75% AMI rent cap). Older, tighter lots in neighborhoods like Whittier or Mapleton Hill face more bulk and setback constraints that can shrink what's actually buildable, even though the underlying rule applies everywhere.
For a buyer weighing two similarly priced Boulder listings, that's the kind of detail that changes which one is actually the better long-term hold, and it's not something a portal listing page is going to surface.
The Financing Change That Landed on Top
One more piece arrived recently enough that it's worth flagging on its own. As of March 2026, Fannie Mae updated its guidelines to let lenders count projected ADU rental income toward a borrower's qualifying income on one-unit, owner-occupied purchase transactions, up to 30% of total qualifying income. That means a buyer looking at a Boulder property with an existing or buildable ADU can potentially use that rental projection during the mortgage underwriting itself, not just as a bonus once a tenant signs a lease. Combined with Boulder's own zoning reform, the timing means a buyer today is looking at a genuinely different set of numbers than a buyer looking at the identical property two years ago.
What This Means If You're Comparing Boulder to the Suburbs
None of this changes Boulder's price point relative to Erie, Broomfield, or the newer master-planned communities further out. It changes what a given Boulder dollar can do once you own the property. A buyer who ruled Boulder out on the assumption that it's still a restrictive, roommate-capped market is working from a rulebook the city itself replaced about a year and a half ago. The real comparison now isn't "how many unrelated people can live here." It's bedroom square footage, lot size and alley access for ADU potential, and whether the numbers still work once you account for the sprinkler line item and a realistic long-term rent, not a best-case one.
If you're weighing a specific Boulder listing against something in Broomfield or Erie and want to know whether the bedroom dimensions and lot actually support this math, that's exactly the kind of question worth running with someone who tracks these ordinances as they change. The team at Peak Home Partners can walk through a specific property's numbers with you before you write an offer.
FAQ
Does this mean there's no limit at all on how many people can live in a Boulder house? No. Occupancy is still capped, just differently. The IPMC ties it to bedroom size and to living and dining room minimums under table 404.5, and a lease can set a stricter limit than the city allows even if the code would technically permit more.
Can I rent out a Boulder ADU without living in the main house? Yes, as of Ordinance 8650, effective March 2025. Boulder no longer requires an owner to occupy either the primary home or the ADU. That's a looser standard than some nearby cities, including Denver, which still ties ADU permits to owner-occupancy of the main house in single-unit zones.
Can a new Boulder ADU be used as a short-term rental? Only if both the ADU and the short-term rental license existed before February 1, 2019. For any ADU built under the current rules, plan on long-term rental income, not nightly bookings.
