You’ve checked your zoning, picked a design, and you’re ready to build your Accessory Dwelling Unit (ADU)—now it’s time for permits.
Permitting is one of the most important (and often most overlooked) steps in the ADU process. Whether you’re building in Phoenix, Gilbert, Mesa, or anywhere across Arizona, understanding the permitting process can save you time, money, and stress.
Here’s a clear breakdown of what to expect—and how to make the process smoother.
What Is an ADU Permit?
A permit is the city’s formal approval to move forward with construction. It ensures your ADU meets:
- Local building codes
- Zoning regulations
- Health and safety standards
For ADUs, this typically includes:
- A building permit
- Possibly electrical, plumbing, and mechanical permits
- Site plan approval showing setbacks, access, and utility connections
What Documents Do You Need?
Every city is a little different, but you’ll usually need:
- A site plan showing where the ADU will go on your property
- Architectural drawings of the building or renovation
- Engineering plans (for foundation, Mechanical, electrical, or plumbing if required)
- A grading or drainage plan, in some cases
- A completed permit application
If you’re using a pre-designed plan, some of these elements may be partially included—but you’ll still need to verify that the design fits your lot and local standards.
How Long Does Permitting Take?
Plan review time frames vary by jurisdiction and time of year. For example, the end of the year a lot of people are taking time off of work and may slow the review process.
Average time frames:
- 3–6 weeks for smaller cities or simpler projects
- 4–8+ weeks in larger cities like Phoenix or if resubmittals are needed
- Add extra time if you’re coordinating with an HOA or planning department for exceptions or variances
Tip: Getting help with your application and plans up front can prevent costly delays later on.
What About HOAs?
Even if your city allows ADUs, homeowners’ associations (HOAs) may have rules about:
- Detached structures
- Design requirements
- Rental restrictions
These don’t override state law, but they can slow things down if approvals are needed. Always check your CC&Rs before submitting to the city.
How PlanHAUS Can Help
At PlanHAUS, we specialize in designing ADUs that are built for permitting success. Whether you’re starting from scratch or modifying an existing layout, we’ll help you:
- Prepare site plans and architectural drawings
- Navigate city or county submission requirements
- Coordinate with HOAs and engineers
- Answer city feedback and resubmittals
