Jackie Krentzman is a Bay Area-based writer and editor.

For many planners and policymakers, missing middle housing is the holy grail of housing. This type of housing — duplexes, triplexes, bungalow courts, and live-work spaces — can provide residents with both affordable housing and an enhanced sense of community. But restrictive zoning, outdated planning systems, and a preference for single-family homes by local residents can make them hard to construct. Some cities are getting creative and examining how they can adjust their rules to spur missing middle housing.

According to Daniel Parolek, a Berkeley-based thought leader on urban planning who coined the term in 2010, one appeal for cities is that it lets local officials talk about the need for more housing choices without triggering fear. We sat down with Parolek, author of “Missing Middle Housing: Thinking Big and Building Small to Respond to the Housing Crisis,” to learn how cities can spur missing middle housing through community engagement, local planning, implementing new or improved local policies, and community-focused zoning changes. Our conversation has been edited for clarity and length.

Jackie Krentzman: Why is this type of housing “missing?”

Dan Parolek: One hundred years ago, most neighborhoods had a mix of single-family homes and houses with multiple units. Then in the 1920s and ‘30s, single-family zoning became the norm, and this mix of housing ground to a halt. The systems needed to deliver these housing choices have disappeared. I often say we’re using 20th century tools to respond to 21st century problems. Most Americans cannot afford to purchase a single-family home, and we need to remove barriers for a broader range of choices.

Zoning changes and parking reform are key to enabling cities to respond to the acute housing shortage in the U.S. There is no one-size-fits-all solution, but there are some best practices, such as form-based zoning, that have been successful. This might involve targeted fixes or a complete rewrite of the zoning or development code. We also developed an approach called the Missing Middle Scan, a quick and cost-efficient analysis designed to help cities identify barriers and opportunities. Some cities, like Modesto, have used this work to inform their housing element and general plan updates.

Why has the appetite for missing middle housing increased over the past 25 years?

Studies have shown that most Americans want to live in walkable, community-oriented neighborhoods, and they are willing to trade off a single-family home for these features. There’s also a growing realization of the health benefits of walking and biking — and fatigue from long commutes. People are tired of getting into their cars. Millennials in particular want a more sustainable lifestyle that prioritizes the climate. Single-person households are rapidly increasing, and these residents want to be near amenities and feel part of a community. Of course, the greatest driver has been the rise in housing prices due to high demand and low inventory.

What sort of zoning reform is needed to encourage missing middle housing?

Zoning wasn’t designed to support today’s housing crisis. Based on our experience with cities across the country, these regulations almost always conflict with adding missing middle housing to new or existing neighborhoods. Much of our work is focused on supplementing and informing housing elements and general plan updates. This leads to targeted fixes or sometimes a complete overhaul of zoning codes.

California has adopted dozens of bills that allow for more units and make it easier to build housing. Local decision-makers can be smart while implementing this legislation by doing so with more nuanced tools, mostly related to form and scale. Some even go beyond what is required. For example, we recently worked with Sacramento on a robust missing middle housing strategy that replaced single-family zoning citywide. The city also removed density caps and paired that with form and scale standards to help ensure smaller, more affordable units.

What can cities tell developers who are unsure if they can meet their profit margins by building missing middle housing?

The per-square-foot construction cost of missing middle housing is more than single-family homes due to building code requirements, but the financial advantage lies in how the land is used. Developers can generate stronger financial returns by increasing the number of units per parcel and help cities meet their housing goals. This is why zoning changes that allow more units are so important. These changes allow developers to multiply revenue without proportionally increasing costs. Smaller units often command a higher price per square foot in walkable neighborhoods due to the growing demand.

Who can benefit from this housing?

Cities of all sizes need this housing. The lowest hanging fruit for any city is in the downtown and downtown adjacent neighborhoods, or any property built before the 1940s, which may already allow multiple units on a lot but still have barriers such as minimum lot sizes and parking in place. Downsizing baby boomers are also a key audience. Many want to sell their single-family home and live someplace smaller near their grandchildren. A good example is a river house project in Healdsburg, a cottage community with a shared community greenspace.

How do you address those community members who are wary of such housing in their neighborhoods?

We start by acknowledging their concerns. Then we talk about how these buildings are “house scale” — they often sit next to single-family homes and most people don’t notice they contain multiple units. We demonstrate visually that if regulations are thoughtfully changed, these housing types can deliver much-needed housing choices.

A primary reason middle housing is gaining traction is because it offers cities a way to talk about the need for more housing choices without triggering fear. I tell cities to avoid using the word “density” because it carries a negative connotation for most people. Instead, we advise cities to show photos of missing middle housing that already exists in their community. We then encourage people to tell their own stories about living in this form of housing, or where their kids, their kids’ teachers, their best friend, or other relatives may live now. Leveraging visual examples and narratives from real people is highly effective and deeply important to us.