Los Altos ADU Guide: Requirements, Cost, Planning & More [2024]

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Benefits of Accessory Dwelling Units

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Los Altos ADU Zoning, Height, & Size Requirements

Before starting your new ADU project, adhere to the following zoning requirements. 

Confirm your home address with the San Jose Permits Office to determine where your Los Altos home or primary residence is zoned. If it is zoned in R-1, R-2, R-M, or PD, you can build your ADU or JADU. If it is not in these zones, you are not permitted to build your ADU or JADU. 

An ADU’s height limit is 16 feet tall for size and height requirements. If you’re building a new ADU with an on-site parking space with a rear and side setback of at least 30 feet, the ADU is permitted to be 19 feet tall. 

The size of an ADU can be up to 800 square feet. If the MFA and MDA approve it, your ADU can be 850 to 1,000 square feet. If your new ADU has on-site parking and a rear and side setback of 30 feet, then the ADU maybe 1,200 square feet in size. 

JADUs can be up to 500 square feet in size or 650 square feet with on-site parking space.

Upgrade your Los Altos home with the perfect ADU

Experience all the benefits that come with building an ADU. Better functionality, increased value, and aesthetics.

Los Altos ADU: Everything to Know

All the information you need to transform your Los Altos home with the perfect ADU addition. Increase your home’s functionality, space, and aesthetics by following the guidelines

Los Altos Setback Requirements

Any new ADU will have a front setback of at least 40 feet, while the rear or side setback should be at least 4 feet. If your new ADU has a rear or side setback of at least 30 feet, add an additional flooring area or higher building height. 

Number of ADUs Around

The state of California now allows single-family homeowners to have an ADU and JADU per lot. For multi-family homes and residences, California allows two detached ADUs, while duplexes can build on any attached ADUs. 


ADU Building

Building an ADU in Los Altos doesn’t require a site development review process or have to meet any design criteria, only the following: 

The ADU design needs to correlate with the design of the home or primary residence. This means the materials used to build the ADU must be the same as those used to build the home, including roofing materials, roof pitch, window types, and exterior and interior walls. 

Furthermore, any exterior lighting for the ADU must be downward-facing or covered. The location of the new ADU cannot be located on any slopes more than 30 percent, within 25 feet of the top of a creekbank, in a recorded easement, critical zone of a heritage park, or near/in a geotechnical or seismic hazard zone.

Permit Types for Los Altos ADU

To build an ADU in Los Altos, you only need a building permit and any related permits. Homeowners wanting to start the process must meet with a planner for the pre-application process. The planner will help homeowners create a checklist of all the documents for zoning, geotechnical reports, and more to apply for the building permit. 


A JADU, or Junior Accessory Dwelling Unit, is a small living space inside an existing home. It’s like carving out a mini-apartment where you already live. This tiny spot has its own place to cook and a separate entrance, but it might share a bathroom with the main house.


Los Altos ADU Parking

Parking for your new ADU should share the same driveway as your primary home. Homeowners cannot add a new driveway to their property for their new ADU. One designated onsite parking space for their new ADU is required. However, there are a few exceptions to this rule. 

The exception to the Los Altos ADU parking is that a parking space made for the new ADU can be located near the setback area. No additional parking space is required for any ADUs within half a mile of a public transit stop.  

If an ADU is created by converting a flooring area with your primary home or all existing ADU structures, a parking space is not required. Similarly, if an ADU was created by demolishing or converting the garage or carport, an on-site parking space does not need to be built or replaced. 

JADUs do not require their own parking space.

Los Altos ADU Types

You can add multiple types of ADUs to your home and property. Each ADU type is different, so research which addition is best for your home. 

Standard ADU

A standard ADU is a small, independent house you can build on the same land as your main house. It's like a second, smaller home with a kitchen, bathroom, and sleeping area. In most cases, this type of ADU is either attached to or detached from the home.

Streamlined SADU

A SADU, or Streamlined Accessory Dwelling Unit, is a small, separate home that can be quickly added to a property. It follows a set of rules that make it easier and faster to get permission to build because it meets specific standards that the city or town has established.

Non-streamlined SADU

A non-streamlined standard attached dwelling unit is a separate living space connected to your main house, like an apartment that shares a wall with your home. Building this kind of space is not as quick because it doesn't follow the faster, simpler rules that some other types of extra living spaces do due to specific paperwork that can take more time to be approved and finished.


A JADU, or Junior Accessory Dwelling Unit, is a small living space inside an existing home. It's like carving out a mini-apartment where you already live. This tiny spot has its own place to cook and a separate entrance, but it might share a bathroom with the main house.



I needed ADU Garage Conversion, and I contacted many contractors for that project. I wanted to make sure to find a reliable contractor for that big project. Finally, I decided to go with Valley Builders and Remodeling. Their price was acceptable, they were available soon, and they gave me the most detailed answers and completely understood what I wanted. The project went OK, the working crew was very professional, responsible, respectful, communicative, and friendly. The project was finished on time and within my budget, and the outcome was excellent. I will highly recommend this contractor and will definitely work with them again on some future projects.

Mike M.

Remodeling may be stressful, but working with Valley Boutique Builders made the process much less so. Roi was fantastic at communicating throughout the remodel, working with me to find solutions, and respecting my home and the shared areas of the condo building. In the end, my house was completely transformed and beyond my expectations in terms of both quality and beauty. I would strongly suggest him and the company! 5 Stars!

Marvin A.

Our experience was truly amazing. We hired them to build an ADU above our garage, and they did a great job. They were flawlessly on budget during the entire project, and it was completed on time, on budget, and in accordance with local regulations. Thank you for making our ADU dream a reality. I will definitely suggest you to anyone wishing to build an ADU on their property. Keep up the good job!

Lakeisha S.

Every Los Altos ADU is different

Find inspiration for yours by viewing recently completed projects.

The Valley Boutique Builder ADU Experience

Choose Valley Boutique Builders for your ADU project and benefit from our expertise in interior design and construction management.

Our proven design-build process ensures that your ADU is tailored to your goals, budget, and timeline. With personalized attention and exceptional service, we keep you informed and involved throughout the entire process.

Count on us to deliver a structurally sound and stunning ADU that exceeds your expectations, creating a remarkable living space.

ADU Permit Application

We guide you through a seamless permit application process.

Custom Accessory Dwelling Unit Design

We make your dream a reality, merging bespoke design with excellent ADU construction.

Build Your Los Altos ADU on Budget

Working closely with your to meet your needs, on time and on budget.

More About Los Altos Accessory Dwelling Units

An ADU, or Accessory Dwelling Unit, is like a smaller house or apartment on the same land as a bigger house. Imagine you have a single big house on a lot, and then in the backyard or maybe attached to the side, there’s a smaller place where someone else can live. This ADU can have its own kitchen, bathroom, and sleeping area, but it’s on the same property as the main house. It’s like a cozy little home within a home. People build ADUs for extra space for family, to rent out for extra income, or even as a home office. They’re a smart way to use land and help with housing shortages in crowded cities.

ADUs typically have their own kitchen, living area, bathroom, and separate entrance, providing complete living facilities for one or more persons. They’ve become increasingly popular solutions for more flexible housing to accommodate family and friends or serve as another form of income. 

ADUs, or accessory dwelling units, come in several flavors, like your favorite ice cream shop, which might have many choices. 

The junior ADU, or the junior attached dwelling unit, is a smaller version of a regular ADU and is a small living space built within the walls of a house you already have. Think of it as turning part of your existing home, like a bedroom, into a little apartment with its kitchen and entrance so someone can live there separately from the main living space. It’s a cozy spot that lets homeowners offer a place to live to someone else, like a family member or a renter, without needing to build something new.

There are detached ADUs or separate little houses in your backyard, like having a tiny neighbor living just next door but still on your property. These are ideal for mother-in-law suites or hosting guests for a long time. 

Then there are attached ADUs, which are connected to your main house—like an extra wing with its door and everything you need to live independently. There’s the garage conversion type, where you transform your car’s home into a cozy nook for a person, adding windows, a bathroom, and a little kitchen. 

Some people have basement conversions, too, turning the space downstairs that might be used for storage into a little apartment.

Finally, there’s the above-garage ADU, like a treehouse for grown-ups. It is built on top of the garage and gives whoever lives there a bird’ s-eye view of the neighborhood. All these types give families more living space or a way to earn extra money by renting them out.

Multiple financial and residential benefits come with adding an attached, detached, or junior ADU, including: 

  • Extra space for entertaining and hosting guests
  • Increased property value when you are ready to sell your home
  • Can be used for extra income 
  • Allows for more privacy on your property 
  • ADUs are also an affordable option for homeowners because it doesn’t require extra pay for land, driveways, etc

ADUs aren’t just for entertaining loved ones and family; you can also create your personal shed for your hobbies, like working on cars, doing arts and crafts, and going to the home gym. The possibilities are endless when you work with Valley Boutique Builders. 

Build Your Ideal ADU in Los Altos with Valley Boutique Builders!

The decision to build an ADU depends on your personal circumstances and goals. ADUs can provide various benefits, including extra living space for family members, rental income, and increased property value.

 Additionally, ADUs are becoming more popular due to the rising cost of housing and the need for more affordable options. However, costs and regulations must also be considered, so it’s important to research and weigh the pros and cons before deciding.

Multiple factors influence the cost of building an ADU, including labor costs, materials, the square footage of the ADU, obtaining permits and licensing, and much more. Consult with a professional before you start any demolition. 

Yes, in Los Altos, California, like in other cities and towns, you typically need a permit before building an ADU. You need to get a building permit, a permit for planning, or a public hearing to start building your ADU. However, it is recommended that those planning to build an ADU read the Los Altos rules and regulations to confirm that their upcoming building meets the zoning requirement before submitting for a building permit. 

Yes, building an ADU with a kitchen must meet these requirements. The kitchen must have a refrigerator, sink, cooktop, oven, or range of at least 10 cubic feet. There must also be enough counter space for food preparation and cabinet space proportional to the ADU. 

The new California law allows homeowners and builders to add two additions to their homes. These additions are an ADU and a JADU, and they can be built on any residential lot. Multi-family homes can build up to two detached ADUs on their lot, but not two attached ADUs. 

Embark on a transformative journey with us and together, we will bring your ADU vision to life and create a space that embodies your style and enhances your Los Altos lifestyle.

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