Colorado lawmakers have proposed a bill that would outlaw single-family zoning in the City of Boulder. Credit: John Herrick

On Wednesday, March 22, Gov. Jared Polis stood in front of the Colorado Capital to announce new legislation that would practically outlaw single-family zoning in cities across the state. 

“We’re at a real fork in the road in Colorado,” Polis said, flanked by dozens of lawmakers, business leaders, environmental advocates and other community members. He capped off the press conference by leading a chant: “More housing now.” 

The 105-page bill, introduced in the Senate that afternoon, would require local governments to meet state standards for land-use and zoning policies, upending decades-old laws that have kept many Colorado cities feeling more like low-density suburbs. 

The bill would allow duplexes, triplexes and townhomes in neighborhoods where only single-family homes are currently allowed. It would also remove hurdles for people to build accessory dwelling units, or ADUs, which are smaller homes built in backyards, basements and garages. And it would make it illegal for cities to impose occupancy limits on the number of unrelated people who can live together. Major cities like Boulder would have until the end of 2024 to come into compliance. 

How, exactly, the bill would override or coexist with Boulder’s existing zoning regulations remains unclear in a number of ways, especially the city’s more granular rules for housing density and design standards. The state legislation comes as city officials and councilmembers consider more incremental changes to zoning, ADUs and occupancy limits

The City of Boulder is yet to take a position on the bill. 

Gov. Jared Polis has made housing a priority during the start of his second term in office. Credit: Anthony Albidrez

Polis was born in Boulder and lives in a condominium near the city’s downtown. His hometown offers some of the greatest potential for housing change — and a potential source of opposition. 

“I’m really glad Polis is pushing this conversation,” Michael Leccese, the chair of the city’s Housing Advisory Board and former executive director of the Urban Land Institute Colorado told Boulder Reporting Lab. “A conversation or shouting match, whatever it is, it’s going to be hot,” he said. 

More than half of Boulder’s residential land area is zoned to only allow single-family homes, according to city data. Such zoning is a relic of the post-World War II suburbs, and it spawned a “neighborhood character” reflected in areas such as Martin Acres, Mapleton Hill and Newlands. 

These low-density land-use policies have also made housing more scarce and more expensive, contributing to segregation by class and race across the county. In Boulder, median home sale price exceeds $1 million. In the last decade, rents have risen faster than people’s incomes. As people spread out in search of more affordable places to live, they end up driving into cities to work, exacerbating climate change from vehicle emissions and making the Front Range’s unhealthy ground-level ozone levels worse. 

The Colorado bill proposed a long list of reforms that would make the state’s largest cities denser. In addition to Boulder, the legislation would impact Lafayette, Longmont and Louisville. 

First, it would prohibit cities from enforcing laws that limit the number of people who can live together based on “family status.” In practically all of Boulder, city code states no more than four unrelated people can live together. Family members, typically defined as marriage, domestic partnership or blood, do not count toward this limit. 

The Boulder City Council is already considering increasing the number of unrelated people who can live together to as many as five. Housing advocates believe the change outlined in the state bill could have the effect of voiding the city’s occupancy limits — though it would still allow cities to impose restrictions based on health, safety and fire codes. 

The bill would also allow ADUs to be built “by right” in single-family neighborhoods. This means if someone wants to build one, they just need a building permit from the city. 

The Boulder City Council is already considering lifting restrictions on ADUs, including ending “saturation limits” on how many can be built in certain neighborhoods. The state bill would go further by also prohibiting off-street parking requirements and banning the condition that the owner of the ADU live in the primary residence. The bill also states cities cannot impose ADU policies that create “unreasonable costs or delays” to getting one built.

The new housing bill would encourage more density near rail stations, which was once planned for Depot Junction. Credit: John Herrick

Perhaps the most attention-grabbing part of the bill is that it would allow “middle” housing in single-family home neighborhoods. The term refers to a type of housing between single-family homes and high-rise apartments, such as duplexes, triplexes and townhomes. 

Theoretically, this provision could increase the city’s housing stock by the tens of thousands, if some single-family homes were converted to duplexes and triplexes. Of the city’s approximate 46,883 housing units, nearly a third — 13,527 — fall within zoning districts that only allow single-family homes, according to city data. 

But converting these homes is easier said than done. 

For one, it’s unclear whether the city has the infrastructure to handle such additional housing. This includes issues with water lines, fire protection, meters, stormwater runoff and car traffic, according to a 2019 city staff memo

Boulder also has a long list of other regulations that limit the size and number of homes that can be built on any given lot. In RL-1 — Boulder’s most common low-density zoning district that includes Mapleton Hill, Chautauqua, Martin Acres and Old North Boulder — a lot must be at least 7,000 square feet for each housing unit. Many of these lots are already maxed out, according to city planners. 

There are also design requirements that limit the buildable area on these lots, including: maximum floor area ratios, which effectively limit how big the overall structure can be, setbacks, height limits, solar shadows, and side yard bulk planes designed to “enhance privacy, preserve some views and visual access to the sky for lots or parcels that are adjacent to new development.” 

It’s unclear whether Boulder would be willing to change these more granular rules, and how they would apply under the new state regulations. In 2019, the Boulder City Council abandoned an effort to allow duplexes and triplexes to be built in some single-family areas, in part due to local opposition. One resident, who said she lived on Linden Ave. for 54 years, wrote in a letter to city councilmembers that “my property values will suffer by this action.” 

In January 2022, the Boulder City Council made it one of its priorities to consider zoning changes to allow duplexes and triplexes in single-family neighborhoods. Earlier this month, before the proposed legislation was introduced, city planners recommended against making changes in single-family neighborhoods, in part because it would require “extensive community outreach” and zoning policy changes that could take years, according to a city staff memo. It cited Minneapolis, which enacted a similar zoning change in 2019. The city was then sued by environmentalists over its implementation. That legal challenge is working its way through the courts

Boulder housing activists and some residents have come out in support of the state legislation. Jill Grano, a former city councilmember and graduate student researcher at CU Boulder’s Boulder Affordable Housing Initiative, said the bill makes “bold steps” to increase housing access. But she would like to see it tweaked to prevent developers from building new multimillion-dollar duplexes. 

“Instead, let’s do what Vancouver did and only allow additional density on single-family lots in exchange for retaining the existing structure,” Grano wrote in an email. “This would bring thoughtful, small, homeowner-driven housing to the market that would inevitably be much more affordable than brand-new, luxury duplexes.”

In response to the introduction of the Colorado housing bill, other Boulder residents are already voicing disapproval. Perhaps in anticipation of a lawsuit, one person wrote on Nextdoor: “Should make for some great legal fireworks at least!” 

In February 2023, the Boulder City Council adopted the position of “qualified support” for “state involvement in land-use matters,” so long as the proposed laws “allow for flexibility in implementation.” 

“At this point, we have no position” on the bill, Carl Castillo, the city’s chief policy advisor, told Boulder Reporting Lab on Thursday. “We’re looking to protect our local government interests and make sure this bill is done right, if it goes forward.” 

Mayor Aaron Brockett stood beside Polis during the announcement of the bill at the statehouse on Wednesday. Brockett did not offer an endorsement. 

“There is still some work to be done,” he said.

John Herrick is a reporter for Boulder Reporting Lab, covering housing, transportation, policing and local government. He previously covered the state Capitol for The Colorado Independent and environmental policy for Email:

Join the Conversation


  1. Glad you mentioned infrastructure. Water, electricity, sewer, fire fighting, etc are all going to be overtaxed with large increases in density. Not mentioned was parking. West Boulder is 125-150 yrs old and these services are not easily amended. Polis would continue to live the life of luxury while telling the rest of us what is best.

    1. These are certainly real concerns, but your comment caught my eye. The article mentions the median home value in Boulder is over $1 million; if you can afford to own a home in Boulder you are probably living a “life of luxury.” I’m not sure attacking Polis’ wealth is a winning message here.

  2. Grano has got something right, without an affordability component, for Boulder this bill will result in zero new affordable units. The housing market in Boulder is inelastic, there are unlimited number of people willing to move here and pay a premium, these new duplexes will just sell for millions. Unless there is an affordability requirement for increased density, new people come to Boulder continue to ruin the place and any goal of affordability is lost. This bill could help on a regional basis, because Broomfield Lafayette Superior markets are elastic and more market units there would increase affordability.

    1. Totally agree Sean. Not to mention, Boulder’s particular issue is exacerbated by CU. Did you know that 65% of our renters are 23 years or younger? That means that a huge driver of our housing challenge is due to CU’s failure to provide on-campus housing for its ever growing student population. If CU built more housing – and it certainly owns enough land to do so – many, many, many dwelling units of all types would open up for non-CU residents. That alone would help alleviate some of the pressure on Boulder’s housing market.

  3. Boulder being such an attractive and limited market will always have a high bar for home ownership and rental rates. Building more housing does not make more affordable housing here.

    ADUs currently have an affordability requirement in exchange for no parking and a larger size. This has been a successful element of Boulder’s rules.

    We have a 25% affordability requirement for new construction on currently zoned properties. Lets increase that requirement if developers get enhanced opportunities.

  4. I agree with the amendment that there must be a requirement for affordable housing, with a definition of what that is, or the whole exercise is for naught. Also that allowances must be made for what is doable in the infrastructure front.

  5. Bring it. Everything in the bill is common sense. The landed gentry will be upset, no doubt, unless they can figure out how to profit from it. That’s why affordability regulations are key per Grano’s suggestions. Not sure if Polis can bring himself to include that, though, which would be an enormous oversight. It will also be expensive to upgrade our infrastructure but the longer we stick our heads in the sand about that the more expensive it becomes. No one thinks infrastructure should ever have to be upgraded but it will have to happen eventually no matter what. Nothing lasts forever. Civilization has its drawbacks.

  6. How will this impact those in the historic districts if they are able to do what the state legislature imposed, if passed?

  7. Can the issue of increased density be voted on by people who already live in Boulder? Currently we are understaffed and underserved in many areas. Let’s put it to a vote this coming November.

  8. Currently Boulder has a number of problems. We are understaffed and under served. How can increasing city density possibly help. Let’s put this to a vote by the people who already live here.

    1. Consider the money one can make in a service job here and then consider the average rent. The math doesn’t really work out. If Polis’ bill does reduce the cost of living as he claims it will, this “staffing” problem would be resolved.

      1. Um, not without an affordability requirement. If you buy a lot of $1 million and build two townhomes on it, you’re going to have two $2 million townhomes. Still not affordable.

  9. I agree with Jill, Sean and Evan that without a permanent affordability requirement, this bill is a developer giveaway. As the planner who developed the original ADU ordinance, I have long favored loosening the requirements. But it is simpleminded to imagine that adding an ADU to an existing home is necessarily increasing affordability – the original property becomes more expensive for sure and without a permanent affordability requirement, the ADU may also be beyond the reach of a target low or middle income population. There’s a good reason why land use decisions are best made locally- each place has unique advantages and disadvantages and its own problems to solve. For the state to eliminate local zoning requirements across the board without affordability, design restrictions and local variations is no solution to anything—

  10. Why this city council’s majority would offer “qualified support” for a state bill that would override our home rule escapes me. It isn’t the state’s role to tell a city – of any size – what its land use or zoning regulations must be. In fact, the Colorado Muncipal League has already stated that ” CML is opposed to state preemption of local authority to adopt and enforce zoning and land use ordinances and any interference with home rule authority granted by Art. XX S. 6 of the Colorado Constitution.”

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