Permit guides

ADU Permits in Los Altos: a Homeowner's Guide

Los Altos gives away ADU plans for free — three sizes, three styles, full drawing sets.

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

Who handles your permit

ADU permits in Los Altos run through the Development Services Department (Planning and Building & Safety divisions). Approval is ministerial — no design review board, no public hearing for a compliant ADU. The city is also actively accepting new designer submissions into its pre-approved plan program.

What you can build

Free plansCity permit-ready detached ADU plans provided free of charge

525 / 854 / 1,190Free plan sizes in sq ft: studio/1-bed, 1-bed, and 2-bed

3 stylesMediterranean, Traditional, and Contemporary

1,200 sq ftMax for a detached ADU under state law

4 ftMinimum side and rear setbacks for detached ADUs

60 daysState deadline for the city to act on a complete application

Free plans — and a pre-approved program on top

Los Altos runs two tracks at once. The permit-ready program offers complete detached ADU drawing sets — structural, mechanical, electrical, and plumbing — free of charge, viewable at City Hall during regular hours. Separately, the Pre-Approved ADU Program lists detached plans from private designers that the Building & Safety and Planning divisions have pre-reviewed; you contract with the designer to use them, then add your property-specific details and pull the building permit.

Free plans still need site work. Even the city's own plans require property-specific adaptation — the right foundation for your soils, utility connections, and siting on your lot. The free set covers the building, not your ground.

What goes into the submittal

Chosen plan set (city permit-ready or designer pre-approved) plus site-specific construction plans
Site plan showing ADU placement, setbacks, and distances to property lines and existing structures
Foundation design matched to site soil conditions
Utility connection plans for water, sewer, and electrical
Title 24 energy compliance documentation

Where applications usually get stuck

Skipping the site-specific work. The most common mistake with free plans is treating them as turnkey — foundation and utility adaptation is where corrections come from.
High-cost-market execution. Los Altos sits in one of the country's priciest construction markets. Shortcuts get expensive fast here — remediation compounds quickly, so the first build needs to be right.
Designer coordination. On the pre-approved track, you're contracting with the plan's designer — clarify who handles site adaptation before you sign.

Not sure where to start? That's the part we do. We check your property against the requirements, coordinate the plans and specialists, and manage the submittal and corrections — one point of contact.

Tell us what you need help with.

Not sure where to start? That's what we're here for.

Send your project

Erik — (916) 540-8960 · Vall — (916) 956-8106
office@pcg-engineering.pro