How Long Does It Take to Get an ADU Permit?

Quick Answer

Getting an accessory dwelling unit (ADU) permit typically takes 2–6 months, though timelines vary significantly by jurisdiction and project complexity. Garage conversions and prefab ADUs on the simpler end may clear permitting in 4–8 weeks, while ground-up new-construction ADUs with design review or variance requests can stretch to 6 months or beyond.

What Affects ADU Permit Timelines?

Several factors determine how quickly your ADU permit moves through the system:

Factor	Impact on Timeline
Jurisdiction	Cities like Los Angeles and Portland have streamlined ADU processes; smaller municipalities may lack dedicated staff
Project type	Conversion (garage, basement) is faster than new construction
Zoning compliance	Projects requiring variances or conditional use permits add 2–4 months
Plan completeness	Incomplete submissions are the #1 cause of delays
Utility connections	New sewer/water connections may require separate permits
Design review	Historic districts or HOA-governed areas add review layers

Typical ADU Permit Timeline by Phase

1. Pre-Application Research (1–2 Weeks)

Before submitting, you need to confirm your property's zoning allows ADUs, understand setback and height requirements, and determine whether your project qualifies for any streamlined approval pathways. Many jurisdictions now offer free pre-application consultations.

2. Plan Preparation (2–6 Weeks)

Hiring an architect or designer and preparing construction documents typically takes 2–6 weeks. Plans must include structural, electrical, plumbing, and energy compliance details. Using pre-approved ADU plans, where available, can reduce this phase significantly.

3. Plan Check Review (4–12 Weeks)

This is usually the longest phase. The building department reviews your plans for code compliance, and corrections are common. First-round plan check takes 4–8 weeks in most cities. If corrections are required, each resubmission adds another 2–4 weeks.

4. Permit Issuance (1–2 Weeks)

Once plans are approved and fees are paid, the actual permit issuance is typically quick, often within a few business days to two weeks.

State-Level Streamlining

California's AB 68 and SB 13 require jurisdictions to approve or deny ADU applications within 60 days of receiving a complete application. Oregon, Washington, and several other states have enacted similar legislation. These laws have significantly reduced permitting timelines in participating states, though the 60-day clock only starts when the application is deemed complete.

Tips to Speed Up Your ADU Permit

• Use pre-approved plans if your city offers them
• Submit complete applications with all required documents on the first try
• Hire an experienced ADU designer familiar with local codes
• Schedule a pre-application meeting to identify potential issues early
• Consider prefab ADUs from manufacturers with pre-engineered plans

Bottom Line

Most homeowners should budget 2–6 months for the ADU permitting process from initial application to permit in hand. The biggest variable is your local jurisdiction's workload and whether your project requires any special reviews or variances.