A guide for building backyard homes in
Walnut Creek, California

Learn about local zoning guidelines, financing options, and getting started with building a custom ADU in Walnut Creek, California.

Type Five City Guide

With the backdrop of Mt.Diablo, Walnut Creek is your cultural and commercial center in Contra Costa. From scenic views to an eclectic collection of culture, it's a perfect place to live and grow.

Bring your family, friends, and neighbors closer with a beautiful backyard home.

Quick ADU Facts

for Walnut Creek, California

You can build an ADU by right in your backyard

An ADU can increase the value of your home

An ADU is easy to finance using your home equity

Walnut Creek Downtown
Walnut Creek Hillside
Walnut Creek Downtown

Prefab vs. traditional built ADUs

Why Type Five offers you the best of both worlds

There are two methods to build a backyard home or ADU: traditional or prefabricated/modular construction. 

Traditional Construction: This is the most common type of construction and involves hiring a contractor to build your home from the ground up. The advantage of traditional construction is that you have more control over the design and construction process. The disadvantages of traditional construction are that it is usually more expensive and takes longer to build.

Prefabricated/Modular Construction: This type of construction involves building your home in a factory and then delivering it to your site. Prefab offers the advantages of faster build times and opportunities to reduce the overall cost of building. However, prefab doesn’t offer the breadth of customization and design flexibility to fit your preferences, the building codes, and the space available for you to build.

At Type Five, our approach combines the best of both worlds, offering you design flexibility with the cost savings and convenience of prefab. Here are some of the notable features:

  • Customizable: Every Type Five ADU is customizable online. You can select the size, color, layout, amenities, bedrooms, finishings, and more without paying thousands of dollars in design fees.

  • Turn-Key Service: Thanks to our streamlined process, you can ditch the chaos and stress of managing the complexities of building your backyard home. We’ll draw up your plans, get them approved by the city, and manage construction, so you don’t have to. Our platform allows us to be your project's architect and general contractor, saving you enormous time and money while giving you the peace of mind that you're getting an amazing service and product.

  • Fast Delivery: A Type Five ADU is usually ready to move in within 4-6 months. Our tightly integrated process from design to build means you can expect to own your ADU shortly after finishing your design. You can expect clear timelines, little to no back and forth, and weeks instead of months of construction on your property.

  • Upfront Guaranteed Pricing: We guarantee your price right in our design process before you even submit a deposit. You can say goodbye to financial surprises & unexpected “change orders” because every project comes with a guaranteed maximum price before the building starts. This means you can accurately budget for the other things in your life… like your retirement or that vacation you’ve been thinking about!

What’s the bottom line? If you want a backyard home but don’t want to deal with the hassle and expense of traditional construction, then prefabricated/modular construction is the way to go. And if you want the convenience of prefab with the flexibility of custom design, then we’ve got your back.

Type Five Pod
Design and customize your ADU online today.
Customizable to your needs
Our modular design system makes it possible to pick the right shape, size, colors, and features.
Move-in ready in 6-8 months
Our turnkey process handles everything from permitting to site work and construction.
Transparent, guaranteed pricing
We remove the abiguity in costs and stay true to your budget.

Experience a turn-key approach

We streamline everything from design to permitting and construction so we can focus on quality where it matters most.

Our Process
Designing an ADU
Configure your ADU with the size, shape, and amenities you want, all online. We’ll translate your design into plans and a guaranteed budget that work for you and your space.
My backyard was challenging to find the right design for, but Type Five was able to offer a number of options that worked for what my Mom was looking for her in her new home.
Michelle R., from Berkeley, California
Permitting an ADU
Our tools generate instant permit sets with unparalleled accuracy, allowing us breeze through your city’s permitting process and setting your project up for a seamless transition to construction.
I was initially dreading the permitting phase of our backyard home project, but Type Five's incredible accuracy and understanding of the local regulations turned it into a stress-free experience. Their team ensured that every detail met the highest standards, which really set my mind at ease. Thanks to them, we moved to construction without a single hitch.
Derek S. from Orinda, California
Building an ADU
As your general contractor, we orchestrate the entire building process using our vetted network of trusted, skilled contractors and sourcing dependable, renewable materials. And we keep our word: you’ll know the cost and timeline from the beginning.
From start to finish, Type Five was transparent and committed to excellence during the build of our ADU. Their network of skilled contractors and dedication to using renewable materials not only aligned with our values but also ensured a product we're proud to show off. Knowing the costs and timeline upfront made planning a breeze.
Ethan M, from San Anselmo, California
Living in an ADU
Our homes are engineered to last. We'll continue to partner with you on maintenance and improvements so that your ADU grows with you.
Our parents love their new ADU. The quality and durability of our Type Five home are apparent in every corner. It's reassuring to know that we have a partner ready to assist us with any maintenance or updates we need as our family's needs change.
Beverly S, from Albany, California

Berkeley's ADU Guidelines

Frequently asked questions about what you can build in Walnut Creek

Can I build an ADU on my property in Walnut Creek?

In Walnut Creek, you can build an Accessory Dwelling Unit (ADU) on your property if it is zoned for single-family or multiple-family dwellings.

Do I need a permit for an ADU in Walnut Creek?

Yes, you need a permit to build an Accessory Dwelling Unit (ADU) in Walnut Creek. The Walnut Creek Municipal Code outlines specific requirements and standards for ADUs in different zoning districts, indicating that both the construction of new ADUs and the conversion of existing structures into ADUs are subject to regulatory approval. This includes attached ADUs within the gross floor area of existing or proposed single-family dwellings, detached ADUs within existing accessory structures, and new detached ADUs subject to size, height, and setback requirements​​

How long does it take to get a permit for an ADU in Walnut Creek?

The average time the city of Walnut Creek takes for your permit application is 60 days of submission. It is possible to get your permit approved within 30-90 days of submission so long as your designs are drawn with the local code in mind.

At Type Five, we take care of your entire permit process. Our ADU plans meet the highest standards of construction and building code across California, ensuring that our permits are approved in the shortest time possible.

How many ADUs can I have in Walnut Creek?

The number of ADUs you can have in Walnut Creek depends on whether or not your lot has a single-family dwelling (and the amount of single-family dwellings on the lot) or has a duplex or multiple-family dwelling on the lot.If you have a lot with one single family dwelling you are allowed 1 ADU and 1 JADU.

If you have a lot with more than one single family dwelling you are allowed 1 ADU and no JADUs.

If you have a lot with a multi-family residence, you are allowed to have up to 2 ADUs.

Is there a minimum lot size for an ADU in Walnut Creek?

There is no minimum lot size requirement for an ADU in Walnut Creek. California state law also mentions that lot coverage requirements can’t preclude the creation of a statewide exemption ADU. A statewide exemption ADU is 800 square feet, with a height limitation of 16 feet and and 4 feet rear and side yard setbacks.

With Type Five, you can design an ADU to fit whatever available space you have in your backyard. Our system can flex and adapt to ensure you can build high-quality livable space even if it's in a smaller area. Get started with designing your ADU here.

Is there a minimum size for an ADU in Walnut Creek?

There is no minimum size for building an ADU in Walnut Creek. California state law gives local governments the ability to set minimum and maximum height standards. However they cannot require a minimum square footage requirement that prohibits an efficiency unit.

Type Five's ADUs can adapt to a variety of different sizes for your needs. Get started with designing yours here.

How big of an ADU can I build in Walnut Creek?

For a one-bedroom or studio ADU, the maximum size for building an ADU in Walnut Creek is 850 square feet; however, if your lot is larger than 15,000 square feet, the maximum can extend up to 950 square feet. For a two-bedroom ADU, the maximum size is 1,000 square feet.

Can you build a two story ADU in Walnut Creek?

In Walnut Creek, the height limit for an Accessory Dwelling Unit (ADU) is generally set at a maximum of 16 feet for detached ADUs. This makes it challenging to incorporate a two story ADU that have a minimum of 7ft of interior ceiling height.

How many bedrooms can an ADU have in Walnut Creek?

There is no limit to the number of bedrooms an ADU can have in the city of Walnut Creek according to California state law. The California HCD ADU handbook states that a limit on the number of bedrooms could be construed as a discriminatory practice towards protected classes, such as familial status, and would be considered a constraint on the development of ADUs.

How close to the property line can I build an ADU in Walnut Creek?

All ADUs built in Walnut Creek and the state of California are required to have 4-foot side and rear yard setbacks. State law allows a local government to determine its own front yard setback requirements. Walnut Creek requires a 20-foot front yard setback.

Does an ADU need its own electrical panel, water meter, or gas meter in Walnut Creek?

In the city of Walnut Creek, an ADU is generally not required to have its own electrical panel, water meter, or gas meter unless the ADU was built at the same time as a new single-family dwelling on the property. However, owners of ADUs that plan to be used as rental units typically install a new set of utility meters to make billing cleaner for tenants.

Are fire sprinklers required in an ADU in Walnut Creek?

You are not required to install fire sprinklers in an ADU in Walnut Creek so long as sprinklers are not required in your main residence.

Is solar required on an ADU in Walnut Creek?

You are generally exempt from installing solar panels on your ADU if your ADU is less than 750 square feet.

How much can I rent an ADU for in Walnut Creek?

You should be able to rent an ADU in Walnut Creek for $2,577, which is the average monthly rent for a one-bedroom apartment so long as the rental term is longer than 30 days.

Can an ADU be used as an AirBnB or short-term rental in Walnut Creek?

You cannot use an ADU as an AirBnB in Walnut Creek unless you are renting it out for a period longer than 30 days. California law states that ADUs created under subdivision (e) of Gov. Code, § 65852.2 cannot be rented for a period less than 30 days. This means you cannot use your ADU as a short-term rental in Walnut Creek.

Can your HOA prevent your ADU build in Walnut Creek?

Your local homeowners association (HOA) cannot prohibit the construction of an ADU or JADU in Walnut Creek. Assembly Bill 670 (2019) and AB 3182 (2020) amended Section 4751, 4740, and 4741 of the Civil Code to preclude common interest developments from prohibiting or unreasonably restricting the construction or use, including the renting or leasing of, an ADU on a lot zoned for single-family residential use.

Covenants, conditions and restrictions (CC&Rs) that either effectively prohibit or unreasonably restrict the construction or use of an ADU or JADU on such lots are void and unenforceable or may be liable for actual damages and payment of a civil penalty.

How does an ADU affect property taxes in Walnut Creek?

The city of Walnut Creek will assess the value of your newly added ADU, typically by using the cost-based method of appraisal, and multiply it by the property tax rate of 1.3%. So, if your ADU in Walnut Creek costs $200,000 to build, you can expect your annual property taxes to increase by $1,300 per year. Adding an ADU to your property will not trigger a reassessment of the value of your primary residence.

How much value does an ADU add in Walnut Creek?

Adding an ADU to your property in Walnut Creek typically adds value to your property, however, the exact amount depends on the appraisal method that your appraiser chooses to use. If an appraiser uses the cost-basis method & the cost of your ADU is $200,000, then you can expect your home value to appreciate by $200,000.

Another method that an appraiser can use is the sales comparison approach, where the value of the ADU addition is determined by recently sold properties in Walnut Creek that included ADUs. However, this approach depends on the number of recently sold properties and there sometimes isn’t enough information to use this approach with ADUs. A back-of-the-envelope way to estimate the value yourself would be to multiply the existing price per square foot of your property by the square footage added by the ADU and compare it to the cost of your ADU. The appreciation is likely in between those two numbers.

How much does it cost to build an ADU in Walnut Creek?

The average cost to build an ADU in Walnut Creek is $230,000. Keep in mind there are a ton of factors to consider when estimating the cost of a project, many of which are unique to your property and sometimes require special surveys to identify. Examples of these factors include whether or not your property is flat or sloped and whether or not you need to upgrade your utilities.

It’s also important to note that converting an existing structure or converting your garage into an ADU isn’t necessarily cheaper than building a brand new detached ADU. You can get an in-depth overview about what goes into the costs of building an ADU in your city on our cost calculator page, or you can get a brief idea of what costs look like below.

Online Resources

Learn more about building in Walnut Creek, California

City of Walnut Creek ADU Permitting Website

City of Walnut Creek ADU Municipal Code

Type Five Pod

Thoughtful design meets unparalleled flexibility.

Type Five brings architectural design and quality to your Berkeley backyard at an unbeatable price.

Type Five makes thoughtfully designed and well-crafted homes for all kinds of life.
Designed in Berkeley, California.