City of Boulder officials want property owners who tear down homes and build larger ones to pay a fee to help pay for affordable housing projects. Credit: John Herrick

The Boulder City Council voted 8-1 last week to allow duplexes and triplexes in single-family neighborhoods, where such homes are currently prohibited. The ordinance is an incremental step toward eliminating a restrictive form of zoning that housing advocates nationwide have long blamed for stifling the supply of housing, driving up costs and exacerbating racial and economic inequities. 

In the City of Boulder, most residential land is zoned for detached single-family homes, making it illegal to build any other type of housing. This has created a suburban feel desirable to many. But it also means homes are relatively scarce, and therefore, often more expensive. 

The new ordinance will take effect on Jan. 1, 2024, according to city officials. 

While its implications are sweeping, the changes for single-family neighborhoods are unlikely to have a dramatic effect in the near term. The ordinance leaves intact density standards that limit the number of housing units allowed on a given lot. As a result, many property owners will not be able to subdivide their homes into duplexes or triplexes. 

City officials estimate that over time, this zoning change will result in about 1,600 additional housing units. 

The zoning changes also seek to encourage developers to build more, smaller housing units in high-density residential areas by altering density calculations. Such changes have been in the works for years. 

“It’s in the weeds,” Mayor Aaron Brockett said of the ordinance during a public hearing late last month. “But I think it’s going to have a really positive impact on development in the community for the decades to come.” 

The zoning changes are somewhat similar to what Colorado lawmakers this year wanted to require of larger cities through statewide land-use legislation. That bill, which was backed by Gov. Jared Polis, failed on the last day of the session, largely due to opposition from local governments. 

Unlike the state bill, the local ordinance has generated relatively little controversy in Boulder. According to the results of a city survey, the concerns included reduced property values, increased car traffic, and a general skepticism that the changes will not reduce housing costs and will benefit developers. 

The changes are not intended to overhaul the city’s zoning code. In January 2022, councilmembers told city officials they wanted staff to come back with a proposed ordinance before the 2023 city election. However, given the relatively tight timeframe — as well as vacancies and turnover in the city’s Planning and Development Services Department, which helped write the code changes — the reforms were always likely to be incremental. 

“We had understood this to be a fairly nuanced and surgical effort,” Brad Mueller, the city’s director for Planning and Development Services, told councilmembers last month. “We know there is more work to be done.” 

The ordinance is the latest in a series of code revisions by the Boulder City Council aimed at creating more housing in the city and potentially driving down costs. Councilmembers have loosened restrictions on accessory dwelling units and raised the city’s occupancy limits. They are also considering changes that would require developers who build larger homes to pay more into the city’s affordable housing program

The latest change would apply to most of the city, in terms of land area. This includes the neighborhoods of Mapleton Hill, Newlands, Old North Boulder and Martin Acres.

While officials were drafting the ordinance and gaining public feedback, some residents suggested that anyone who converts a single-family home to a duplex or triplex should be required to sign a covenant that makes the new home deed-restricted as permanently affordable. 

But city officials rejected this idea. They said it would be a disincentive for property owners to convert their homes to duplexes, and make it less likely developers would build them. Also, anyone who adds additional housing units to a property is required under the city’s inclusionary housing program to pay a fee that the city uses to subsidize affordable housing elsewhere. 

In addition to eliminating single-family zoning, councilmembers amended the city’s zoning code to encourage the construction of smaller homes and relaxed parking requirements. 

The Boulder City Council has approved zoning changes to encourage developers to build more, smaller housing units in certain apartment and condo projects. Credit: John Herrick

More dense apartments and condos 

In mixed-use and high-density residential areas, the ordinance adjusts how the city calculates density to encourage more, smaller housing units. This is achieved by eliminating open space requirements and calculating density limits based on floor area ratios. Currently, density is achieved by requiring a minimum lot size for each dwelling unit.  

These changes would apply to the neighborhoods such as Whittier, Goss-Grove and University Hill.  

Relaxing parking requirements

Current city code requires developers to provide 1.25 off-street parking spaces for each housing unit in certain developments. The ordinance reduces that to one car spot per unit. 

The change also allows developers to build fewer parking spots than required under city code without going through the site review process. Sometimes the city’s Planning Board reviews such requests. In recent years, the board has almost always approved requests for minor parking reductions. 

Some transportation advocates want the city to eliminate its off-street parking requirements altogether. 

Parking mandates, they argue, increase the costs of building housing. It costs developers about $40,000 per spot to build below-grade parking, according to a recent estimate from city officials. Because those costs are typically passed onto tenants, people who do not own cars are essentially subsidizing car ownership for others. 

Depending who is elected this November, parking reform is likely to be a priority for the next Boulder City Council.

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:

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  1. John, the headline is misleading. They didn’t eliminate single family zones. They allowed duplexes and triplexes on certain very large lots.

    1. It is my understanding that technically, come Jan. 1, no zoning districts will only allow single-family homes. This includes RR-1, RR-2, RE, and RL-1. As the story points out, this might not have much of a practical effect, given the density requirements. I hope the headline and the story make it clear that this is not a zoning overhaul, not was it intended to be. But it is a step toward something much bigger.

  2. I find it interesting that Boulder continues to encourage new builds and, in this case, allow for more duplexes, etc., yet they continually complain about traffic congestion. Seems like an oxymoron.

    1. Congestion comes from people commuting into the city. More people within the city with access to our transit and bike infrastructure leads to fewer cars and less congestion

  3. It was not controversial because Boulder residents are completely tuned out on this issue. Boulder Progressives get a win for their base and real estate overlords, with a reform that will build zero affordable or middle income units, these duplexes will be extremely high end investment units, not housing for normal people.

    1. This is one of the incremental steps. The end goal is to encourage more smaller and affordable homes to be built, hence reducing the pressure on housing market, reduce cost and per-capita emission. It’s best done state wide to create the desired impact.

      Who is that one vote against this ordinance?

  4. It won’t change rent levels at all. That’s what the progressives don’t seem to get. More density, without regulation on price, only gets you more density.

    1. The goal is to increase housing supply. Multiplex units are also typically smaller by internal square footage than single family houses, much more so when lot sizes are considered. More smaller homes will drop prices. Density is not an issue unless we fail to offer alternate means of getting around. But perhaps by “regulation” you mean preventing these units from being purchased as investment properties? If so, we should absolutely ensure these homes only go to owners and not to the investor class.

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