The Boulder City Council is expected to direct city staff to draft an ordinance that would allow duplexes and triplexes in neighborhoods where they are prohibited. Credit: Uwe Lubjuhn

Update 8/23/2023: On Aug. 23, City of Boulder planners are presenting a draft ordinance to the House Advisory Board that would allow duplexes and triplexes in single-family neighborhoods and tweak density requirements to encourage smaller, more affordable homes. City council is expected to hold a public hearing and vote on the ordinance on Sept. 21.

Update 6/15/2023: On June 15, in an expected move, the city council directed city staff to draft an ordinance that would allow duplexes and triplexes on larger lots in single-family neighborhoods, where they’re currently prohibited. A majority of councilmembers also said they want to increase the city’s occupancy limit from three unrelated people to five in low-density residential zones.

Earlier this year, Colorado lawmakers sought to outlaw single-family zoning in certain areas of certain cities. The bill died on the last day of the legislative session, in part due to opposition from city leaders who stood to lose power over land-use decisions. 

The Boulder City Council, however, voted to lobby in support of the bill. Now, with its demise, councilmembers are considering similar zoning reforms on their own. 

On Thursday, June 15, the city council is expected to direct city planners to draft an ordinance to allow duplexes and triplexes in neighborhoods where they are currently prohibited. An ordinance could be voted on as soon as September, according to city officials. 

The changes would be part of a larger housing reform package that has been in the works since 2021, when councilmembers made it one of their top priorities to increase the supply of housing in Boulder. The goal is to drive down costs so more people can live here. 

“At the end of the day, our school enrollment is dropping, and we are not getting the needed families in those areas,” Councilmember Matt Benjamin said during a recent city council study session. 

At the request of councilmembers, city officials are also drafting code changes that would loosen open space and floor area requirements in higher-density residential areas to encourage developers to build smaller housing units. Another potential ordinance would increase the number of unrelated people who can live together from three to as many as five. 

The city has been collecting feedback from residents on the overall zoning reform plan. Supporters believe it will improve housing affordability. Opponents cite additional car traffic, potential sewage issues and a loss in property values, among other concerns, according to a city staff memo.

The proposal to allow duplexes and triplexes in single-family neighborhoods would apply to the city’s low-density zoning districts. Together, these districts include about 13,500 of the city’s 47,000 housing units. But they cover most of the city’s residential land area. The current restrictions on multifamily housing have created a suburban aesthetic in areas such as Martin Acres, Mapleton Hill and Newlands.

The changes would not be immediate — nor all that drastic. 

City officials are not proposing to change density standards that cap the number of dwelling units per acre. Nor are they proposing to change development standards, such as floor area ratios or height limits, which effectively limit the overall buildable area on a given lot. 

In practical terms, this means only property owners whose lots are large enough to subdivide and build another single-family detached home would now have the option to convert their home to a duplex or triplex. 

Over time, the changes could allow for as many as 1,500 additional housing units, according to Karl Guiler, a policy adviser for Planning and Development Services. 

Separately, earlier this month, Gov. Jared Polis signed a law that effectively prohibits cities like Boulder from enforcing residential housing growth caps. Boulder’s law, commonly known as the Danish Plan (after Paul Danish), was passed in 1976 as part of an effort to slow growth. The latest iteration of the growth ordinance caps new home building permits at 1% per year.

The city’s ordinance exempts housing units in mixed-use areas — those that allow homes and businesses — and deed-restricted affordable housing from the annual limit. As a result, in the last decade, the growth gap hasn’t blocked the construction of new housing, according to city officials. 

John Herrick is senior 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 He is interested in stories about people, power and fairness. Email:

Join the Conversation


  1. The proposal for duplexes won’t make a bit of difference in house prices. These will be either spec units built for high end or they won’t be built at all. The economics of Boulder mean the housing market is expensive. Also, smaller units aren’t what people want. Maybe folks who tell other people how to live want smaller units but families with children want a yard, space, enough bedrooms etc. Why do you think folks are moving to Longmont?

    1. Lots of people are willing to sacrifice space to live in a desirable location. The shift in perspective is happening here and all over the world as we all come to grips with the realities of climate change, economics and the importance of “community.” Yes, Longmont and similar “suburban” areas will continue to grow. But they are still fundamentally driven by having a car to do anything and that is not a sustainable or desirable plan. “Fill in” options are the only way to keep Boulder from becoming a “rich-only” enclave. Boulder has walkability in most areas (except East where it looks more like suburbs), carless living is possible and a sense of community is palpable. Please keep an open mind about the future of Boulder.

      1. Dorie, the economics of housing are such that an expensive, desirable, resort community like Boulder will always be expensive. Period. Boulder has a very good – though imperfect – permanently affordable housing program. But this council is pursuing a basket of proposals that will not result in more housing that is affordablet to low or moderate income residents. Increasing the occupancy limits – which the voters already rejected – will serve students, who should be served by CU while harming families who rent. (Students will pay per person rents while family pay per family – so expect 5 people to pay $1500 a person, creating a total rent of of $9,000, which few families who rent can afford.) Allowing duplexes and triplexes on large lots – something previous councils rejected — will not produce housing that is affordable to anyone but the wealthiest. Why? Because to buy a large lot will cost about $2 million (land in Boulder is precious) and anyone who buys at that rate will build dwelling units that guarantee a significant return on that investment (i.e. dwellings that cost at least $4 million – to cover cost of land, labor, plus profit). If you want affordability you have to REGULATE for it. If this council wants occupancy limits to address affordability, they have to develop a mechanism that GUARANTEES affordability for those rentors. This legislation does not have such a mechanism. If they want affordability through allowing duplexes on large lots, they have to REGULATE for it. I understand people’s emotional response to proposals to increase density. But density is not a solution for affordability. Density is a solution for density. Period.

      2. Dorie, apologies. My math was off. 5 individuals paying $1500 each results in a total rent of $7500. The point still stands: most families who rent can’t afford that so we will lose even more families who move elsewhere. The City keeps having to solve CU’s problem. Did you know that 65% of Boulder’s renters are 23 or younger? That means college kids. All because CU only houses freshmen and a small percentage of other students. So each year, CU – which keeps growing – dumps 25,000 students into the Boulder housing market where landlords increase rents every year (captive market) and more and more working people and families have to compete with these students for housing. Why do you think Longmont has exploded? Because so many families can find a house they can afford to buy there. Whereas here in Boulder many houses and townhomes have been turned into dumps by unscupulous landlords who prey on students. Increasing occupancy will only make that problem worse.

    2. I agree. Families do not seem to be welcomed, so they are moving to other places. Small, starter home neighborhoods should have been built at Junction Square instead of the tons of ugly, dense condos that are not family-friendly. I’ve lived in Boulder since 1963, and until the past 5 to 10 years, Boulder loved families. It’s no wonder that grade-school enrollment is dropping.

  2. Grade school enrollment is falling because families don’t want to bring up children in condos and apartments where there is nowhere to play. Rather than allowing the tall, ugly condos and apartments, Boulder should have encouraged builders to build single-family neighborhoods with small affordable houses and pocket parks.

  3. I’m siding with Sarah on this one. Boulder is such a desirable place to live, that the demand for housing is “inelastic.” That is, increasing the number of houses, will not make the houses cheaper. There are too many rich people who want to move to Boulder, and can afford to pay the “market rate” for housing. However exorbitant that market rate is.I really don’t understand City Council’s rationale here.

  4. One of the ironies of Sarah’s argument is that most people who fight against more housing in their city would prefer to make the argument that it will cause the values of their homes to plummet. This is a very effective argument that has been wielded for decades to prevent all kinds of housing from being built. The problem with that argument is that it’s indefensible (and always has been) and as Sarah points out, density by itself is not a solution for affordability when demand overwhelms supply. So, now whenever any kind of proposal is set forth for any kind of housing that isn’t regulated as Affordable you hear the opposite argument that it will make housing more expensive. Or if that’s too bold, then at least it will not make housing more affordable. Her argument to this effect is juxtaposed with the claim that what families really want are large houses with large yards instead of the small, yardless condos that the imagined finger-wagging YIMBY’s who support this reform are trying to pack them into. This argument is laugh-out-loud funny to me because the proposal as described in the article is for houses on lots that are so large that you could build another single-family home on them without stretching the units per acre standard or the floor area ratios. That scenario does not exactly evoke the Little Old Woman Who Lived in a Shoe much less most people’s idea of “increased density”. We live in a time when the overwhelming trend is to have every aspect of land use and housing over regulated – everything from what color your HOA will let you paint your garage door, to who your roommates can be, to whether a single-family home on a large lot can be turned into a duplex. To characterize this very modest liberalization of the zoning code as arising from moralizing activists who like to “tell people how to live” is just plain silly.

    Most housing experts I have listened to agree that there is no one solution to the affordable housing crisis in North American cities and I think Sarah and I agree that this particular reform is not going to make any difference to housing affordability as broadly defined in Boulder. (Although I would point out that the difference between being able to afford a $4M home and a $2M home is quite large and that some people would even prefer to squeeze out this second and perhaps less desirable category of rich people.) Some people think that the only new housing that should be built should be regulated as permanently affordable. This is one of the most effective ways to make sure that new housing supply is sharply curtailed especially in rich neighborhoods where it gets regulated to the point of being infeasible.

  5. Thanks Philip for a reasonable response to this thread. First there is complaint that no one wants to live in small condos with no yard despite abundant evidence that plenty residents do want that– then complaints that such homes are right next to the Pearl St. junction — which is exactly where they should be built–catering to those who enjoy living right next to google/target and the main urban corridor without having to drive or even ride a bike. And walking to the pocket parks that are abundant along goose creek/valmont right in the neighborhood. I just don’t understand the logic behind nilly willy rejection of any change in land use, any new builds regardless of how sensable and appropriate for the specific location. Reject and complain for the sake of winning brownie points from fellow contrarians? Is that what this community has devolved to? How about we say at least two positive things about each proposal for every negative (but constructive) criticism we give? Being this critical of every little thing reduces the dialogue among neighbors–about anything. Why stick your neck out to make any kind of comment if all you get is very negative response to even the most reasonable idea?

  6. Housing needs to be regulated if you want it to be affordable. That much is evident. Expand and improve the affordable housing options. Stop catering to market developers and wealthy landowners looking to maximize profits.

  7. I would agree with several people on here that regulating for affordability is about the only way to make it really possible in Boulder due to the extreme imbalance between supply and demand and the already extremely high land values. However, this will ultimately have to be done at the state level due to a 1981 state law that bans rent control. A few years back “the Supreme Court of Colorado ruled that requiring developers to set aside a portion of units that would be rented at below-market-rate in new projects is illegal. It is considered a form of rent control that was banned by the state legislature in 1981.”

Leave a comment
Boulder Reporting Lab comments policy
All comments require an editor's review. BRL reserves the right to delete or turn off comments at any time. Please read our comments policy before commenting.

Your email address will not be published. Required fields are marked *