ADU Permits in Los Altos: The 2026 Process, Fees, and Timeline

Los Altos processes ADU permits ministerially under the California state baseline: a decision within 60 days of a complete application, no public hearing, no neighbor approval, and a guaranteed right to a detached ADU on nearly any single-family lot (Government Code sections 66310 to 66342). State law preempts any stricter local rule, so the statewide framework, up to 1,200 square feet detached, 4 foot side and rear setbacks, no owner-occupancy requirement, is the operative rulebook.

The short version: Los Altos follows the state ADU baseline, and its quarter-acre-plus lots are among the easiest canvases in our service area: room for a full-size unit without crowding the main home. The permit is objective and bounded; the design question is what to do with all that space. We run the whole process, with a permitting budget built into one project price.

The Los Altos ADU permit process, step by step

1. Start with what state law guarantees. Up to 1,200 square feet detached where standards allow, never less than an 800 square foot, 16 foot unit, 4 foot side and rear setbacks, and at most one parking space with broad exemptions. Citations in our Can I build? rules lookup.
2. Take stock of your lot. Los Altos zoning favors large parcels, quarter-acre and up is common, which means most lots comfortably fit even our biggest homes while preserving yard. Placement usually optimizes for privacy and utility runs rather than squeezing between setbacks.
3. Design and engineer the plans. Site plan, floor plans, structural, and Title 24, drawn to the city’s objective standards. Complete packages clear plan check in one round far more often.
4. Submit and manage review. The 60-day ministerial clock runs from completeness. No hearings, no subjectivity.
5. Permit, build in parallel, inspect. Foundation and utilities on site while the home is built in the factory, then crane set and final inspection.

On our projects every step above is handled for you, with a permitting budget built into the one project price. Your exact permit and city fees are set by Los Altos and confirmed in your feasibility study.

What big lots change

On a 10,000 square foot Los Altos parcel, the size conversation flips: instead of asking what fits, you choose what serves the plan. Our 1,200 square foot Twelve Hundred three-bedroom at $549,000, all-inclusive of construction, works as a genuine second house for parents or adult children, while the U-shaped Twelve Hundred U at $599,000 adds a private courtyard feel. Owners optimizing for rental yield often still pick the 749 square foot two-bedroom at $369,000, because it stays under the impact-fee threshold and rents strongly in a city with Silicon Valley commute access.

That is the real Los Altos question, income, family housing, or long-term value, and our guide to whether an ADU is worth it plus the Santa Clara County ADU regulations guide frame it well.

Los Altos ADU fees

The state fee structure governs the major items: impact fees are waived for ADUs under 750 square feet, and at 750 square feet or larger they must be proportional to the primary dwelling. School fees on larger units and building permit fees that scale with valuation belong in the budget too. Your feasibility study itemizes every fee for your address, and all of it is included in your contract price, so the fee schedule is our problem, not yours.

How long the permit takes

Expect the 60-day ministerial window from a complete application, with design and plan preparation in front of it. Review pace sits with the city; what we control is the overlap: your home is about 97% built in our Salinas factory, roughly 65 minutes away, while Los Altos reviews the plans. On delivery day the home arrives essentially finished, which your neighbors will appreciate. The full schedule is in our Los Altos ADU timeline guide.

Frequently asked questions

How big an ADU can I build in Los Altos?

State law allows detached ADUs up to 1,200 square feet, and Los Altos’s large lots mean that maximum is realistically buildable on most parcels, unlike cities where setbacks eat the envelope. Your free property analysis confirms the exact envelope for your address.

Do I need to add parking?

At most one space, with broad state exemptions: near transit, replacing a garage, or converting existing space. On most Los Altos lots the long driveway already solves it even where a space is required.

Can I build an ADU for my parents and rent it later?

Yes. No owner-occupancy requirement applies to standard ADUs, so the same unit can house family now and become a long-term rental later. Many of our clients plan exactly that sequence; see our multigenerational living guide.

Does an ADU make financial sense at Los Altos property values?

High land values cut both ways: construction is the same price, but every permitted square foot appraises at Los Altos rates, and rental demand from Silicon Valley is deep. Run your numbers in the ROI calculator, then pressure-test them in a feasibility study.

See what your Los Altos lot supports

A big lot deserves a real plan, placement, utilities, and the right model, not guesswork. Book a free property analysis and our team will map your options; expect about 30 minutes, at no charge.