Los Altos · Santa Clara County
ADU Design & Build in Los Altos, California
Los Altos lots and tree ordinances reward a design-build team that knows how to thread the needle on setbacks and protected trees.
Building ADUs in Los Altos, California
SHAPE designs and builds accessory dwelling units for homeowners in Los Altos, California, across North Los Altos, Old Los Altos, Country Club, Highlands-Magdalena, and the Loyola Corners area.
Los Altos' single-family lots are large enough to support a serious detached ADU, and the school district and downtown draw steady long-term-rental demand. Multigenerational families are the fastest-growing use case we see here.
We're a licensed California general contractor (CSLB #1158688) with an in-house architecture and modular construction team. That means one contract, one fixed price, and one team responsible from the first site walk through final inspection with the Los Altos building department.
Los Altos ADU Rules at a Glance
- Setbacks: California state law caps rear and side setbacks for new ADUs at 4 feet, and Los Altos follows that standard.
- Height: Los Altos limits detached ADUs to one story and 16 feet. Attached ADUs can reach 16 feet or the main house's height limit, whichever is greater.
- Maximum size: 850 sq ft for a one-bedroom ADU and 1,200 sq ft for two or more bedrooms. Space above 850 sq ft cannot push the lot over its lot coverage or floor area limits. Los Altos also has protected-tree rules we handle inside the design package.
- JADUs: Junior ADUs (up to 500 sq ft) are allowed inside the existing footprint of the primary home, in addition to a detached ADU on most single-family lots.
- Setbacks from the house: A detached ADU sits at least 5 feet from the main house. Setting it at least 10 feet from the side and rear lines waives the daylight plane rule.
- City plans: Los Altos offers free Permit-Ready ADU plans at 525, 854 and 1,190 sq ft in three styles, with no changes allowed.
- Parking: No replacement parking is required when a garage or carport is converted or torn down to build an ADU, wherever the lot is. Separately, no parking can be required for the ADU itself within one half-mile walking distance of public transit.
Rules checked September 2026 against: City of Los Altos ADU page, Los Altos ADU ordinance, Chapter 14.14, HCD ADU Handbook, California Energy Commission ADU guidance, Santa Clara County Assessor, Santa Clara County ADU Resource Center. City rules change often. We confirm the rules for your lot before design.
SHAPE handles the full permit package with the Los Altos planning department, zoning verification, building plans, Title 24 energy, and every correction cycle, so you don't have to learn the code.
Real permit & build timelines in Los Altos
| Planning + building permit | 10 – 16 weeks |
| Factory + site build | 8 – 16 weeks |
| Typical city permit fees | $10,000 – $16,000 |
Ranges reflect SHAPE projects in Los Altos across 2024–2026. Fees are city permit fees only; SHAPE construction quote is separate and fixed.
Recent Los Altos projects
| Neighborhood | Size | Timeline | All-in price |
|---|---|---|---|
| North Los Altos | 800 sq ft · 2 BR | 3.5 months from permit | $459k all-in |
| Country Club | 1,100 sq ft · 2 BR + den | 4 months | $539k all-in |
| Highlands-Magdalena | 600 sq ft · 1 BR | 3 months | $349k all-in |
Our Process
- Site assessment. We walk your Los Altos lot, confirm setbacks and utility locations, and give you a feasibility read and an all-in price the same week.
- Design. Our in-house architects design the ADU around your lot, your family, and your budget, with fixed pricing before you sign.
- Permits. We submit, respond to every planning and building comment, and drive the file to permit issuance with Los Altos.
- Build. Modules are fabricated in our facility while site work, foundation, utilities, landscaping, runs in parallel. Set and finish happen on site.
Frequently asked
- How much does an ADU cost in Los Altos?
- SHAPE's published prices start at $223,000 for Model 1, $263,000 for Model 2, and $343,000 for Model 2X on a typical lot. The final fixed quote in Los Altos depends on size, finishes, utilities, access, and site conditions.
- How long do permits take in Los Altos?
- California law requires ministerial ADU review within 60 days of a complete submittal. Real-world timelines in Los Altos typically run 2–4 months including corrections. SHAPE manages every submittal and response with the Los Altos planning department.
- Do I need to add parking for an ADU in Los Altos?
- Often, no. No parking can be required for an ADU within a half-mile walking distance of public transit, and no replacement parking is required when a garage or carport is converted or torn down to build the ADU. We check your lot's distance to transit during feasibility.
- What size ADU can I build in Los Altos?
- Los Altos allows 850 sq ft for a one-bedroom ADU and 1,200 sq ft for two or more bedrooms, as long as the space above 850 sq ft fits within the lot's coverage and floor area limits. On top of local rules, California state law guarantees at least 800 sq ft on most single-family lots regardless of local FAR limits.
- Can I rent out an ADU in Los Altos?
- Yes. California state law allows long-term (30+ day) rentals of ADUs statewide. Short-term rentals are set by the city, Los Altos, like most Bay Area jurisdictions, restricts or prohibits stays under 30 days.
- How strict is Los Altos on protected trees?
- Los Altos actively protects mature heritage trees, an arborist report is often required as part of the ADU permit. We design around drip lines from the start and coordinate with the city arborist before permit submittal.
- Can I build a larger ADU on a Los Altos flag lot?
- Yes. Flag lots and larger single-family parcels in Los Altos routinely support the full 1,200 sq ft detached ADU. We confirm FAR and lot coverage during feasibility.
- Should I use the city's free permit-ready plans or go custom?
- The city's Permit-Ready plans (525, 854 and 1,190 square feet) save design fees, but no changes are allowed. If your lot has protected trees, an odd shape, or a layout you have in mind, a custom design usually fits better. We can price both on the same lot.
- Will a 1,200 square foot ADU fit under my floor area limit?
- Maybe. Los Altos allows 1,200 square feet for two or more bedrooms, but the space above 850 square feet cannot push the lot over its coverage or floor area limits. We run those numbers on your survey before design starts.
- How does the daylight plane work for a Los Altos ADU?
- The daylight plane limits how high a building can rise near a property line. Setting a detached ADU at least 10 feet from the side and rear lines waives the rule. Second-story windows within 15 feet of a property line on attached ADUs need a 5-foot sill height.
- Can I build an ADU on any Los Altos lot?
- Yes, on any lot with an existing or proposed single-family home. State law does not allow a minimum lot size for ADUs. In Los Altos the practical limits are floor area, lot coverage and protected trees.
- How many bedrooms can a Los Altos ADU have?
- State law does not let cities cap the number of bedrooms in an ADU. In Los Altos the bedroom count sets the size allowance: 850 square feet for one bedroom and 1,200 for two or more.
- Does a Los Altos ADU need solar panels?
- A new detached ADU does. Under the 2025 California Energy Code it needs new solar panels, which can be added to an existing system elsewhere on the property. An attached ADU counts as an addition and does not need solar.
- Will an ADU raise my property taxes in Los Altos?
- Only on the new building. The Santa Clara County Assessor does not reassess your existing home. It assesses the ADU at market value when it is finished, or partly on January 1 if construction is still underway.
- Can I sell the ADU separately?
- No. Los Altos's ADU code does not allow separate sale, and the city has not adopted the state's optional condominium route under AB 1033.
- Can I build the ADU and a new main house at the same time?
- Yes. State law lets the city approve both together, and the ADU is still reviewed without discretionary review. When the two are built together, utilities can treat the ADU as new residential use for connection fees.
- Can I legalize an older unit built without permits?
- Often, yes, if it was built before 2020. State law (AB 2533) bars impact fees and penalties for those units, though the city can deny one that is substantially unsafe. We can assess what it would take to bring yours up to code.
- Is the California $40,000 ADU grant still available?
- No. CalHFA's ADU Grant paid up to $40,000 toward predevelopment costs, and CalHFA says its latest round was fully allocated in December 2023. CalHFA warns that anyone offering to get you one is running a scam.
- How long does PG&E take to connect an ADU?
- PG&E reported ADU electric hookups averaging about 300 days from request for projects finished by August 2025, and says its average for new service had dropped to 118 days by March 2026. We file with PG&E when the permit goes in so power is not the last thing we wait on.
Nearby cities we serve
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