Princeton ADU Permits & Fees [2026]
By-right zoning, 30–60 day approval timeline. Zoning permit, construction permit, utility fees, and inspection schedule.
Permit Types & Costs
Zoning Permit
Confirms the ADU is permitted and meets bulk standards (setbacks, height, coverage).
Cost: $300–$800
Construction Permit (Building)
Covers structural, electrical, plumbing, and general safety compliance.
Cost: $4K–$8K (detached)
Electrical & Plumbing Permits
Separate permits for electrical and plumbing work.
Cost: $2K–$4K combined
Utility Connection Fees
Water, sewer, electric connections. Detached ADU fees typically capped at 50% of primary dwelling fee.
Cost: $2K–$5K (varies by utility)
Timeline
Typical Approval Timeline: 30–60 Days
Week 1: Submit zoning + construction permit applications
Week 2–4: Plan review; clarifications if needed
Week 4–6: Permit issuance (no major revisions)
After: Begin construction; inspections at foundation, utilities, final
Ready to Start Your Permit Process?
Contact a local ADU contractor or architect to prepare plans and handle permitting.