ADU Builder in Los Altos
Los Altos Hills is one of California’s most distinctive residential communities — a hillside town of about 8,000 residents with a minimum lot size of one acre, no commercial development, and no downtown. Every parcel here is a genuine estate, surrounded by mature oaks and open space.
An ADU on a Los Altos Hills property occupies a different category than in any other city in this set. On a one-to-five-acre parcel, a detached guest cottage or caretaker’s unit isn’t a compromise — it’s a natural extension of the estate. The regulation framework reflects the town’s character: a tiered system where the default ADU size is 800 sq ft, but lots that can accommodate 30-foot side and rear setbacks with on-site parking unlock 1,200 sq ft and 19-ft height. On most LAH lots, those thresholds are achievable, and the extra planning up front pays off in a meaningfully larger unit.
ADU Regulations in Los Altos Hills
ADUs in Los Altos Hill must follow specific setbacks, height, and size requirements. A new ADU must maintain a minimum front setback of 40 feet from street frontages and at least four feet from side and rear property lines. If the ADU provides a least 30-foot side and rear setbacks, it may qualify for additional floor area and increase height.
The standard height limit for a new ADU is 16 feet. This can be increased to 19 feet if the design includes an on-site parking space and meets the 30-foot side and rear setback requirement. By default, properties may build an ADU up to 800 square feet. Depending on Maximum Development Area (MDA) and Maximum Floor Area (MFA), ADUs may be expanded to 850 square feet for studios or one-bedroom units, or up to 1,000 square feet for two-bedroom units. If on-site parking is provided and setbacks meet 30 feet, the maximum ADU size may reach 1,200 square feet.
Build Your ADU in Los Altos Hills
Start with ParcelZ. Enter your address and get instant eligibility, your buildable area, and matching floor plans. Free, no signup, under 60 seconds. Then our team takes it from there.
The Los Altos Hills ADU Permitting Process
Los Altos Hills uses a two-step permitting process — a Planning Department zoning approval precedes the building permit application. This is more involved than single-step permit portals used in most other cities, and it means the design needs to be fully resolved (setbacks, size tier, height, parking) before the first submittal. Getting this right upfront prevents delays between planning approval and building permit issuance.
Free Feasibility Study
Apex calculates your lot’s MDA and MFA, identifies which size tier applies, confirms the front/side/rear setback constraints, and determines whether the 30-ft setback + parking bonus is achievable on your specific parcel. This shapes every design decision before any drawings are produced.
Select a Floor Plan
Once the tier is confirmed, Apex selects a floor plan sized to the appropriate maximum: 800, 850, 1,000, or 1,200 sq ft. On large LAH lots, the 1,200 sq ft two-bedroom plan is the most common target. Height is designed to the 16 or 19 ft limit based on the tier.
Planning Department Submittal
Apex prepares the zoning approval package — site plan, architectural drawings, setback documentation, and MDA/MFA calculations, and submits to the Los Altos Hills Planning Department. This step confirms zoning compliance before building permit work begins.
Building Permit Application
Once planning approval is issued, Apex files the full building permit package: structural drawings, Title 24 energy calculations, utility plans, and any required demolition documents.
Construction & Inspections
Apex manages the build under city inspector oversight, coordinates all required inspections, and delivers the completed unit with a Certificate of Occupancy.
Why Build an ADU in Los Altos Hills?
An ADU in Los Altos Hills provides versatile space to support your lifestyle. It can serve as a home office, art studio, or guest home, giving family members or visitors privacy and independence while keeping everyone close
ADUs are also a smart financial investment. Renting out an ADU can generate steady passive income, helping offset expenses or serve as a long-term investment. In a high-demand area like Los Altos Hills, ADUs are attractive to renters seeking modern, private living spaces,
In addition, building an ADU can increase your property’s overall value. Homes with ADUs often stand out in the market, offering extra living space, rental potential, and flexible options for family or future use, all while making efficient use of you existing lot.
Have questions? Contact Apex Homes Today
Our team knows Los Altos Hills’ zoning, permits, and pricing inside out. Call us for a free, no-pressure conversation about your property. We’ll tell you exactly what’s possible.