Affordable Accessory Dwelling Units

Prospect Newtown, in Longmont, CO, has seamlessly integrated affordable housing by creating a host of accessory dwelling units (ADUs). The ADUs are perfectly blended within the town overall—and actually help contribute to the development’s success.

2 minute read

December 6, 2014, 5:00 AM PST

By Danielle Lauren


Accessory Dwelling Unit

radcliffe dacanay / Flickr

Set on the 80-acre site of his family’s former tree farm only a 10-minute drive from Boulder, Prospect Newtown was conceived of by developer Kiki Wallace in the mid-1990s. Attracted to New Urbanism’s tenets of walkable, livable communities, Wallace decided to create a development based on these ideals.

Wallace hired renown New Urbanist architects Duany Plater-Zyberk (DPZ) to carry out his vision. Over the last twenty years, and throughout multiple building phases, Prospect has become a thriving new kind of suburban community. Kids run along sidewalks on narrow tree-lined streets, a town center beckons locals with shops, restaurants, and offices, along with a community park, and a mix of home types—including townhomes, detached houses, live/work spaces, and lofts above retail—attract residents with a variety of architectural styles.

ADUs are a vital component of this plan. Originally, city ordinances required that 10% of new housing needed to be affordable, with no specifics to how this should be done. As a result, Wallace and DPZ decided that ADUs would fill this role. Set above detached garages or behind homes, and generally around 500-650 square feet, these units rent for around $1,000 and are eminently popular with renters and homeowners alike. “By virtue of their location, they act as naturally occurring affordable housing,” says Wallace. “There’s no need to mandate or regulate them.” There are currently around 325 townhomes, condos, lofts, and houses in Prospect—and some 150 additional ADUs.

First and foremost, the planners knew that ADUs had to appeal to homeowners to make them successful. To ensure that “homeowners don’t feel threatened and that renters have privacy” as Wallace describes, thoughtful design included creating separate entrances, making sure that ADUs’ windows didn’t look into the backyard, and placing them behind homes so they feel distinct from the main residence. Though initially the first owners of ADUs all said they wouldn’t rent them out, within six months, all of the first ADUs were completely rented since as Wallace says, “There’s no invasion of privacy, and they bring in subsidies for the landlord.”

Friday, December 5, 2014 in Build a Better Burb

portrait of professional woman

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching. Mary G., Urban Planner

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching.

Mary G., Urban Planner

Get top-rated, practical training

Close-up of "Apartment for rent" sign in red text on black background in front of blurred building

Trump Administration Could Effectively End Housing Voucher Program

Federal officials are eyeing major cuts to the Section 8 program that helps millions of low-income households pay rent.

April 21, 2025 - Housing Wire

Logo for Planetizen Federal Action Tracker with black and white image of U.S. Capitol with water ripple overlay.

Planetizen Federal Action Tracker

A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.

April 30, 2025 - Diana Ionescu

Close-up on Canadian flag with Canada Parliament building blurred in background.

Canada vs. Kamala: Whose Liberal Housing Platform Comes Out on Top?

As Canada votes for a new Prime Minister, what can America learn from the leading liberal candidate of its neighbor to the north?

April 28, 2025 - Benjamin Schneider

Bluebird sitting on branch of green bush.

Wildlife Rebounds After the Eaton Fire

Following the devastation of the Eaton Fire, the return of wildlife and the regrowth of native plants are offering powerful signs of resilience and renewal.

47 seconds ago - AP News

1984 Olympics

LA to Replace Inglewood Light Rail Project With Bus Shuttles

LA Metro says the change is in response to community engagement and that the new design will be ready before the 2028 Olympic Games.

49 minutes ago - Newsweek

Close-up on woman in white and blue striped knee-length dress standing next to mint green cruiser bike resting against low wrought iron fence in front of green lawn.

Paris Voters Approve More Car-Free Streets

Paris Mayor Anne Hidalgo says the city will develop a plan to close 500 streets to car traffic and add new bike and pedestrian infrastructure after a referendum on the proposal passed with 66 percent of the vote.

2 hours ago - domus

Urban Design for Planners 1: Software Tools

This six-course series explores essential urban design concepts using open source software and equips planners with the tools they need to participate fully in the urban design process.

Planning for Universal Design

Learn the tools for implementing Universal Design in planning regulations.