Accessory Dwelling Unit Permit Guide
ADUs usually require zoning review, building permits, utility planning, fire and life-safety review, and inspections from foundation through final approval.
Reviewed July 26, 2026
Almost always required for detached ADUs, garage apartments, basement apartments, and new independent dwelling units.
$1,000-$10,000+ in permit, impact, utility, and review costs depending on location and scope.
Two to six months is common where plan review, utility review, and zoning checks are required.
Cost and timing ranges are general planning examples, not local quotes. Verify the current fee schedule, review queue, and inspection availability with the offices serving the property.
Common permit triggers
- Separate kitchen
- Separate entrance
- Detached dwelling
- Rental or long-term occupancy use
Documents to gather before applying
- Site plan
- Architectural plans
- Energy documentation
- Utility and sewer information
- Fire separation details
Inspection sequence to plan around
- Foundation or slab inspection
- Framing and trade rough-ins
- Insulation and fire separation
- Final building and utility inspections
Mistakes that create delays
- Assuming a guest room is not a dwelling unit
- Missing utility capacity questions
- Ignoring parking or owner-occupancy rules
- Starting construction before zoning approval
State and city variation
State ADU laws may limit local restrictions, but city zoning, utility, and building-code review still control the permit.
Contractor questions
- Who is responsible for pulling the permit?
- Will the permit list the full scope of work?
- Which inspections must happen before work is covered?
- Are permit fees, corrections, and reinspection fees included in the quote?
- Will I receive copies of approvals and final inspection records?
Build a project checklist
Use the checklist tool to prepare documents and inspection questions in your browser. No email address is required.
Open checklist tool