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Permit guides

ADU Permits in Palo Alto: a Homeowner's Guide

What you can build, which permits you need, and how the review actually works — in plain language.

Last updated October 2026. Rules change; always confirm current requirements with the city or county before you build.

Who handles your permit

Everything runs through Planning and Development Services, and everything is electronic: all applications, plans, and supporting documents go through Accela Citizen Access (ACA) — instructions at paloalto.gov/BuildingPermit. The Development Center is at 285 Hamilton Avenue (First Floor), Palo Alto, CA 94301 — (650) 329-2496. Palo Alto enforces the 2025 California Building Standards Code as adopted in the municipal code, and the submittal rules are famously precise — the file-naming convention alone can bounce an application.

What you can build

California state law sets the baseline, and Palo Alto follows it:

The three-file submittal — and pre-reviewed plans in progress

Palo Alto's submittal checklist allows exactly three PDF files per review cycle, named C#_address_PLAN, C#_address_APPLY, and C#_address_DOCS — C1 for the first round, C2 after corrections. The PLAN file bundles the cover sheet, structural plans, site and civil plans, architectural drawings, and landscape plans including a T-1 tree-protection sheet. The APPLY file carries the utilities application, residential valuation form, and temporary-power application.

On pre-reviewed designs, the city has been building toward an AB 1332 preapproved-ADU gallery with state grant support — check the city's site for the current gallery before committing to a designer. And Palo Alto explicitly encourages talking with your neighbors before you submit: its review culture is neighbor-sensitive, and early conversations prevent late objections.

What goes into the submittal

• Utilities application and residential valuation form
• Site plan (existing and proposed), plus grading, drainage, and site-improvement plan
• Topographic / boundary survey
• Architectural plans: floor plans, roof and reflected-ceiling plans, exterior elevations, building sections
• Structural plans, details, and calculations
• CALGreen forms — Mandatory plus Tier 2 (sheet GB-1) for a detached ADU
• Landscape plans, including the T-1 tree-protection sheet
• Planning entitlement approval letter, if one applies to your project

Where applications usually get stuck

• File-naming discipline. Misnamed or extra files bounce the submittal instead of being reviewed — get the C#_address format right.
• Tree protection is taken seriously. The T-1 sheet and arborist review slow projects near significant trees; removals are rarely easy.
• Municipal utilities. Palo Alto runs its own electric, gas, and water (CPAU), so service upgrades and temporary power route through the city, not PG&E — a different coordination path than most neighbors' lots.
• Late neighbor objections in a review culture that hears them out — talk to neighbors before you file.
• CALGreen Tier 2 on top of Mandatory for detached ADUs — an extra compliance layer that smaller plans sometimes miss.