All you need to know about building ADUs in
Alameda County, California
Learn about Alameda County's ADU regulations, find homes that fit your backyard, and kickstart your journey to constructing a personalized ADU.
Where the city hums, the coast beckons, and adventure is always on the horizon. From Oakland's vibrant street art to Berkeley's eclectic charm, there's no shortage of cool spots to explore. Sip artisan coffee, savor international cuisine, or simply bask in the California sun by the bay. Alameda County – it's all about the good times, every time.
Bring your family and friends together with an inviting backyard residence in Alameda County.
Prefab vs. stick built ADUs
Trove gives you the best of both approaches
When it comes to crafting your backyard haven, you've got two routes:
traditional construction or the speedy prefab/modular path.
Traditional Construction: This is the familiar journey, where a contractor brings your ADU to life, granting you full creative command. Yet, this path often demands more time and money.
Prefab/Modular Construction: Here, your ADU is birthed in a factory before it graces your site, promising swift assembly and potential cost savings. However, it might not satisfy your unique tastes or location-specific requirements.
At Trove, we fuse these worlds, offering you the best of both.
Customizable: Every Trove ADU can be tailored to your liking online. From
size and color to layout, amenities, bedrooms, and finishings, you're in
control, without costly design fees.
Fast Delivery: A Trove ADU is typically move-in ready in just 4-6 months. Say goodbye to long, drawn-out construction projects with our efficient process.
Upfront Pricing: No surprises here! We know your price during the design phase, so you can budget with confidence, avoiding unexpected financial hurdles.
In essence, if you crave a backyard retreat without the hassle and costs
of traditional construction, prefab/modular construction is your path.
And if you desire prefab's ease with custom design options, look no
further - we've got your back.
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Alameda County ADU FAQs
Common questions about what you can build in Alameda County
What is an ADU?
An ADU is an accessory dwelling unit. It is a secondary housing unit on a single-family residential lot. ADUs go by many names, including granny flats, in-law units, backyard cottages, secondary units, and more.
Can I build an ADU on my property in Alameda County?
ADUs are permitted in Alameda County in accordance with state law. A single-family dwelling is allowed to create at least one ADU. Owner-occupied single-family properties have the option to build one ADU and one Junior ADU. Meanwhile, multi-family properties containing four or more existing residential units are permitted to construct one ADU. These ADUs may be constructed as new units or converted from existing space, and they can be either detached, attached, or Junior ADUs.
How long does it take to get a permit for an ADU in Alameda County?
The city of Alameda County is generally required to review your permit application within 60 days of submission. However, if your designs align with the local code, it's feasible to secure permit approval within a 30-90 day timeframe from the date of submission.
How many ADUs are allowed per property in Alameda County?
According to state regulations, a single-family residence in Alameda County can establish a minimum of one Accessory Dwelling Unit (ADU). Owner-occupied single-family homes also have the option to create one ADU and one Junior ADU. Multi-family properties featuring four or more existing residential units may construct one ADU. Nonetheless, the precise number of ADUs permissible on your property may be subject to local zoning regulations. We recommend reaching out to the city of Alameda County and your local zoning authority to ascertain the specific limits on ADU numbers for your property.
Are there any specific lot size requirements for ADUs in Alameda County?
Alameda County does not impose a minimum lot size requirement for Accessory Dwelling Units (ADUs). Additionally, California state law explicitly states that lot coverage regulations should not hinder the construction of a statewide exemption ADU.
What are the size restrictions for ADUs in Alameda County?
The state law allows ADUs up to 800 sq. ft., with specific jurisdictions allowing up to 1200 sq. ft. From our research, it looks like the maximum ADU size in Alameda County is 1200 sq. ft. However, you should check with your city for the most up-to-date regulations. Eave's system is designed to align with these guidelines, ensuring compliance with regulations and adapting to the available space for construction.
What is the typical rental rate for an ADU in Alameda County?
You can typically rent an ADU in Alameda County for approximately $2,822.29 per month, which aligns with the average monthly rent for a one-bedroom apartment, provided that the rental term exceeds 30 days. It's important to note that for ADUs constructed before December 31, 2024, there is no owner-occupancy requirement.
Is it permissible to utilize an ADU as an Airbnb or short-term rental in Alameda County?
In Alameda County, you are not allowed to utilize an ADU as an Airbnb unless you are renting it for a period exceeding 30 days. According to California law, ADUs constructed under subdivision (e) of Gov. Code, § 65852.2 cannot be rented for durations less than 30 days. Consequently, the use of your ADU as a short-term rental in Alameda County is prohibited.
Can your HOA impede the construction of an ADU in Alameda County?
No, your local homeowners association (HOA) is not permitted to prevent the construction of an ADU or JADU in Alameda County. Assembly Bill 670 (2019) and AB 3182 (2020) introduced amendments to Section 4751, 4740, and 4741 of the Civil Code, which expressly prohibit common interest developments from obstructing or unreasonably restricting the construction, use, rental, or leasing of an ADU on a lot zoned for single-family residential use. Any covenants, conditions, and restrictions (CC&Rs) that effectively hinder or unreasonably limit the construction or utilization of an ADU or JADU on such lots are rendered void and unenforceable, or the HOA may be liable for actual damages and civil penalties.
What is the impact of an ADU on property taxes in Alameda County?
In Alameda County, the city will evaluate the value of your newly constructed ADU, usually utilizing the cost-based appraisal method, and then multiply it by the property tax rate of 1%. For instance, if your ADU costs $220,000 to build, you can anticipate an annual property tax increase of approximately $2,200. Importantly, the addition of an ADU to your property will not prompt a reassessment of the value of your primary residence.
How does the addition of an ADU impact property value in Alameda County?
In Alameda County, integrating an ADU into your property typically enhances its overall value. However, the precise amount of this increase is contingent on the appraisal method employed by your appraiser. If the cost-basis method is utilized and the ADU's construction cost is $220,000, you can anticipate a corresponding increase of $220,000 in your property's value. An alternate appraisal approach is the sales comparison method, in which the ADU's value is determined by analyzing recently sold properties in Alameda County that feature ADUs. Nevertheless, the applicability of this method depends on the availability of a sufficient number of recent property sales with ADUs, which may not always be the case. For a rough estimate, you can also calculate the added value yourself by multiplying the current price per square foot of your property by the square footage contributed by the ADU and then compare it to the cost of constructing the ADU. The actual value appreciation is likely to fall somewhere between these two figures.
What is the typical cost of constructing an ADU in Alameda County?
The average cost to build an ADU in Alameda County is approximately $220,000. It's essential to consider that numerous factors impact the project cost, many of which are specific to your property and may necessitate special surveys for assessment. Factors include whether your property is flat or sloped and if utility upgrades are necessary. Additionally, it's worth highlighting that converting an existing structure or repurposing your garage into an ADU does not necessarily result in lower costs compared to constructing a brand-new detached ADU. You can gain a comprehensive understanding of the various components contributing to ADU construction costs in your city by utilizing Eave's design tool to tailor your ADU project to your specific needs.
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