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Accessory Dwelling Units (ADU)
City of Phoenix Standard Plan Library
The ADU Standard Plan Library offers pre-approved designs for detached accessory dwelling units (ADUs), created through the 2024 City of Phoenix & AIA Phoenix Metro Design Competition. These plans help reduce construction time and cost. The plans are free to use for City of Phoenix residents. Residents must submit plans as is without modifications.
2024 Design Competition Winners
The City of Phoenix, in partnership with AIA Phoenix Metro, proudly hosted the 2024 Accessory Dwelling Unit (ADU) Design Competition—an open call for innovative, sustainable, and practical ADU designs. Supported by a national AIA College of Fellows Component Grant, the competition attracted talented entrants from across multiple states, showcasing creative solutions for housing in Phoenix.
On December 3, 2024, winners were announced during a special ceremony at Phoenix City Hall, featuring remarks by Mayor Kate Gallego. The jury-selected finalists underwent an additional City of Phoenix review to ensure designs could be easily adapted into standard plans for local use.
Beyond the competition criteria, the City team evaluated additional parameters, including:
- Ease of conversion to standard plans for permitting
- Compatibility with typical Phoenix lot sizes (6,000–8,000 sq. ft.)
- Strategies to reduce material costs and improve affordability
This initiative marks the first step in creating a comprehensive ADU Standard Plan Library for Phoenix—providing residents with accessible, pre-approved designs to support housing flexibility for years to come.
What's Next?
Approved ADU standard plans will be available at no cost to residents. A plot/site plan will still be required for permitting, but the design fee barrier is removed, making ADUs more attainable for homeowners.
Select your design: Browse the list of standard plans. Contact information for each designer is provided and may be contacted for questions. Please be aware that any changes to the approved standard plans will require a new submittal outside of this process.
What is an Accessory Dwelling Unit (ADU)?
ADUs, often referred to as guest houses, casistas, or granny flats are separate, self-continued living areas that are either fully detached structures or attached to an existing home, with its own external kitchen.
An ADU usually contains all of the amenities to operate as a fully independent, operational dwelling, including a kitchen, bathroom, living area and sleeping quarters.
New Rules
In late 2024, the Phoenix City Council approved new ordinance changes to comply with new state laws for ADUs.
Learn More:
Frequently Asked Questions
Check your HOA rules about accessory structures.
When a lot has no more than one single-family detached primary dwelling, two ADUs are permitted in addition to the primary dwelling unit. A third ADU may be pemittd under certain circumstances. Typical single-family zones are: R1-6, R-1-10...etc.
Use My Community Map to find out the zoning district for your home.
Each zoning district has “lot coverage" guidelines that define how much of your property can be covered by buildings or structures. The new guest house rules allow two ADUs per lot (and even three on certain lots), and each ADU may be up to 75% of the gross floor area of the main house (not to exceed 1,000 sf for lot up to 10,000 sf or 3,000 sf for lots over 10,000 sf).
In My Community Map, link to the Phoenix Zoning Ordinance to determine the lot coverage allowance for your home.
Find your property on the Maricopa County Assessor's Office website. It will list your official lot size as well as the dimensions of the structures on your property. You can use these two figures to make a rough calculation of your current lot coverage.