Building a backyard guesthouse in Tempe is about to get faster, cheaper, and far less complicated.
The City of Tempe has wrapped up its inaugural Accessory Dwelling Unit (ADU) Design Challenge, selecting 10 pre-approved casita designs that homeowners will soon be able to use with an expedited permitting process. City officials say the new plan library responds to growing interest in ADUs, fueled in part by recent state legislation requiring cities to allow them on single-family lots.
City planners saw the demand coming. Questions about ADUs were already pouring in, according to Tempe Principal Planner Jacob Payne, prompting the city to look for ways to reduce barriers before homeowners were overwhelmed by cost and red tape.
Modeled after similar programs in Tucson and Phoenix, Tempe’s contest was supported by a $20,000 AARP Community Challenge grant, which funded prize money for architects and outreach to residents. The response was broad: 23 design teams from Arizona, California, and New York submitted proposals, with concepts ranging from ultra-compact units to accessible and sustainability-focused designs.
Community input played a major role. A jury made up of architects, Arizona State University faculty, and planning professionals reviewed the entries, while nearly 500 residents weighed in through online voting. That feedback helped steer the final selections toward smaller, more affordable casitas that could fit comfortably into existing backyards without sacrificing pools or mature landscaping.
The winning designs blend architectural quality with desert practicality — incorporating features like passive cooling, efficient layouts, and materials suited for Tempe’s climate. While ADUs typically have little visual impact on neighborhoods, Payne says they offer meaningful gains for the city’s housing supply.
The 10 designs will now form Tempe’s new Standard Plan Library, giving homeowners a curated set of options that are already vetted by the city. Instead of starting from scratch, residents can browse the designs, contact the architect, and purchase a license — capped at $5,000 and often costing much less — before moving directly into the permitting stage.
That shortcut can translate into major savings. Custom ADU designs can cost tens of thousands of dollars in architectural fees alone, while pre-approved plans also eliminate much of the time and expense tied to plan review.
City officials view ADUs as one tool — not a cure-all — for addressing housing needs. Casitas can provide space for extended family, aging relatives, or renters, all while maintaining neighborhood character. Early signs suggest strong momentum: after just four ADUs were built under Tempe’s earlier pilot program, the city has already received 73 applications so far this year.
Tempe plans to roll out an ADU dashboard to track trends and expects to expand the Standard Plan Library next year, inviting additional designers to participate. For now, residents can explore the initial set of winning designs through the city’s official Standard Plan Library at https://www.tempe.gov/StandardPlanLibrary, offering a head start for anyone considering a backyard home.
