California ADU Laws: Guide to 2025 Rules & Regulations, and download the free California ADU Handbook

As Accessory Dwelling Units (ADUs) and Junior Accessory Dwelling Units (JADUs) emerge as essential components in addressing California's housing needs, understanding the current state laws is crucial for homeowners. The California Department of Housing and Community Development (HCD) continuously updates its guidance to reflect the evolving legal framework, aiming for clarity and consistency.

What are ADUs and JADUs?

An ADU is an attached or detached residential dwelling unit providing complete, independent living facilities for one or more persons on a lot with a proposed or existing primary residence. It must include permanent provisions for living, sleeping, eating, cooking, and sanitation. ADUs can take many forms, including efficiency units and manufactured homes.

A JADU, on the other hand, is a smaller unit, no more than 500 square feet, that is contained entirely within a single-family residence. A JADU can have separate sanitation facilities or share them with the existing structure. Only one JADU is permitted per lot zoned for single-family residences.

The Benefits of Building an ADU in California

ADUs offer a wide range of advantages for California homeowners and the state's housing supply:

• Affordability: ADUs are an affordable type of home to construct because they do not require paying for land, major new infrastructure, structured parking, or elevators. They are often built with cost-effective wood frame construction, which is significantly less costly than new multifamily infill buildings.

• Income Potential: ADUs can serve as a valuable source of income for homeowners through rent.

• Family Proximity and Aging in Place: These units allow extended families to live near one another while maintaining privacy. They also give homeowners the flexibility to share independent living areas with family members and others, facilitating older adults' ability to age in place.

• Housing Supply: ADUs are making a difference in the housing crisis. Between 2016 and 2023, the number of ADUs permitted annually in California grew 20-fold, from 1,336 to 26,924. In 2023, ADUs made up over 21% of all homes permitted statewide.

Key Regulatory Standards for ADUs

Understanding the rules governing ADU development is essential to a smooth permitting process.

Permitting and Timing

ADUs that are subject to State ADU Law must be reviewed, approved, or denied ministerially—meaning without discretionary review or a hearing. The review is based on objective standards that involve no personal or subjective judgment.

A permitting agency generally has 60 days to approve or deny a complete ADU or JADU application if an existing dwelling is on the lot. If the agency fails to act within 60 days of receiving a completed application, the permit is "deemed approved".

Owner-Occupancy and Rental Terms

A local agency cannot impose an owner-occupancy requirement on any ADU. However, local agencies can require that ADUs be used for rentals with terms longer than 30 days. For JADUs, the owner must reside in either the remaining portion of the primary residence or in the newly created JADU, with limited exceptions.

Size and Height Limitations

While local agencies may set maximum unit sizes by ordinance, they must allow an ADU of at least 850 square feet, or 1,000 square feet for ADUs with more than one bedroom. Also, conversion ADUs—created from existing space within a primary dwelling or accessory structure—are not subject to these unit size requirements.

A local agency may impose height limits, but they may not be less than:

• Detached ADUs: 16 feet on a lot with a proposed or existing single-family or multifamily dwelling unit. This increases to 18 feet if the lot is within a half-mile walking distance of a major transit stop or a high-quality transit corridor.

• Attached ADUs: 25 feet, or the height limitation that applies to the primary dwelling in the local zoning ordinance, whichever is lower.

Setbacks and Parking

For an attached or detached ADU, a setback of no more than four feet from the side and rear lot lines can be required. Importantly, no setback is required for an ADU or JADU created within an existing living area or accessory structure, or an ADU created in a new structure in the same location and to the same dimensions as an existing structure.

Local agencies are prohibited from imposing parking standards on ADUs in a number of specific circumstances, including ADUs located within a half-mile walking distance of public transit, or ADUs that are part of the proposed or existing primary residence or an accessory structure. In general, parking requirements cannot exceed one space per unit or bedroom, whichever is less. Furthermore, if a garage or carport is demolished or converted for an ADU, the local agency shall not require that those off-street parking spaces for the primary unit be replaced.

Overcoming Homeowners Association (HOA) Restrictions

Covenants, conditions, and restrictions (CC&Rs) and operating rules that effectively prohibit or unreasonably restrict the construction or use of an ADU or JADU on lots zoned for single-family residential uses are void and unenforceable under the Civil Code. HOAs may impose limited objective standards on an ADU or JADU, such as requiring specific materials or architectural styles, but these standards cannot unreasonably increase the cost to build or effectively prohibit construction. HOAs may not influence a local agency's ministerial approval of an ADU or JADU.

Unpermitted Structures Built Before 2020

A local agency is precluded from denying a permit for an unpermitted ADU or JADU constructed before January 1, 2020, because the unit violates building standards, State ADU Law, or a local ordinance. Denial is only permitted if correcting the violation is necessary to protect public health and safety, or if the building is deemed substandard. Homeowners applying for a permit for a previously unpermitted ADU or JADU constructed before January 1, 2020, may also be exempt from impact fees or connection/capacity charges if they provide written evidence that their household income does not exceed the definition of a low- or moderate-income household.

Start Your ADU Journey with Confidence

The process of building an ADU can seem complex, but by understanding the State's ADU laws and leveraging expert resources, California homeowners can successfully navigate the process. HCD provides resources and technical assistance on these matters through its online ADU Portal.

As you prepare to unlock your property’s potential, remember that having the right tools and information is key. We offer specialized resources to simplify the complex journey from concept to completion:

• California ADU Handbook: This free official handbook provides comprehensive guidance directly from the California Department of Housing and Community Development (HCD).

• ADU Ebook: Your Complete Guide to California ADUs: This comprehensive guide dives deeper into the regulatory details, design options, and local considerations to ensure you start your project fully informed.

• How To Finance an ADU Ebook: Navigate the financial landscape with our expert breakdown of loans, grants, and strategic financing options to make your ADU investment a reality.

• Pre-Approved ADU Plans for Sale: Save time and avoid costly revisions by starting with code-compliant, thoughtfully designed ADU plans engineered for California's unique requirements.

Empower your project with the clarity and expertise you need to build with confidence.

Detached ADU Cost & Comprehensive Build Guide: Everything You Need for Your Backyard Cottage

Introduction

A Detached Accessory Dwelling Unit (ADU or DADU for short), often called a backyard cottage, granny flat, or carriage house, is the ultimate way to maximize property value, generate passive income, and provide flexible living space.

Unlike attached units or garage conversions, a detached ADU is a standalone structure built from the ground up, offering superior privacy and design freedom. But what exactly does it take to build one, and what is the true cost?

This comprehensive guide breaks down the financial, regulatory, and logistical steps to successfully complete your detached ADU project, ensuring you turn your backyard into a powerful asset.

I. The Detached ADU Cost Breakdown: Why They Cost More Than Conversions

Detached ADUs typically command a higher initial price tag than some other common ADU types due to critical site work and utility connections. Understanding this upfront will help you budget effectively. But there are major benefits for choosing a detached ADU. Remember that price isn’t the only, and shouldn’t always be the most important, deciding factor for what type of ADU to pursue.

The current national cost range for a newly built detached ADU generally falls between $250 to $500+ per square foot, but your final number depends heavily on location, design complexity, and material finishes.

As an aside, I mention cost per square foot here, but I personally find that to be a terrible way to estimate the true cost of an ADU. Smaller ADUs have a much higher cost per square foot than larger ones as there is an economy of scale. Small ADUs still need all the expensive parts like kitchens, bathrooms, mechanical, electrical, and plumbing systems. A better estimated price range would be to assume most ADUs will fall in the $200,000 to $500,000 range depending on size, complexity of design, quality of materials, and site conditions. Size is only one aspect of determining the final price.

Unique Cost Drivers for Detached ADU Construction

To accurately budget your project, pay special attention to these expenses, which are unique to detached structures:

FURTHER READING: For a deep dive into financing your ADU, get our Ebook:
How to Finance Your ADU: A Guide to Loans, HELOCs & Creative Financing.

II. Detached ADU Design & Zoning Requirements

The single biggest differentiator between a successful ADU investment and a stalled project is your command of zoning requirements and their strategic application to design. It’s not simply about checking boxes; it’s about viewing local ordinances as the design DNA of your detached unit. A design firm that’s an expert in ADUs understands that setbacks, height restrictions, and lot coverage rules are not barriers—they are the constraints within which they engineer maximum value, and rentable space. By mastering these parameters early, the design team ensures the design is not just compliant, but is an elegant solution that anticipates permitting challenges, ultimately safeguarding your budget and timeline from the outset. It is also recommended that homeowners read their local zoning codes and ADU regulations so they know what is allowed and what to expect. This can help you pick the best design if you are going with a pre-designed ADU plan, or have better conversations with your custom design team.

Zoning: Setbacks, Lot Coverage, and Height Restrictions

1. Setbacks: Defining the Location
Setbacks determine how close your Detached ADU (D-ADU) can be built to the property lines. They are a critical factor because they dictate the location and also may impact the maximum width and length of your structure.

• State vs. Local Rules: While many state laws (like in California) mandate minimum setbacks as little as 4 feet from the side and rear property lines, local jurisdictions may impose stricter rules or looser ones. These local overlays often relate to fire safety, utility access, or neighborhood design review, and you must adhere to the strictest applicable rule.

• Strategic Placement: Understanding corner lot rules, front yard exceptions, and the necessity of fire access paths is essential for maximizing the usable space allowed by the setbacks.

2. Lot Coverage: Managing Site Density
Maximum lot coverage regulates the total percentage of your lot area that can be covered by all structures, including the primary home, garage, and the new D-ADU. This is a common bottleneck for properties with small yards or large main houses. Often local regulations will limit the footprint of structures rather than the full square footage of built area, so make sure you check your zoning code to see what is allowed or contact an experienced ADU designer in your area.

• Calculating Density: For example, if your lot is 5,000 square feet and the maximum coverage is 40%, only 2,000 square feet of structures are allowed. If your house already uses 1,800 square feet, your ADU is limited to a mere 200 square feet.

• The Exemption Angle: If your lot coverage is limiting what you can build, knowledgeable designers will look for local exemptions, such as rules that exclude features like permeable patios, trellises, or specific foundation types from the lot coverage calculation, allowing you to maximize the buildable footprint of the ADU itself.

3. Height Restrictions: Unlocking Multi-Story Design
Height limits are imposed to ensure the ADU remains subordinate in scale to the primary home and to mitigate concerns about shadowing or excessive bulk from neighbors. Most jurisdictions restrict D-ADU height, often between 16 and 25 feet.

• The Two-Story Challenge: This restriction is vital if you plan for a two-story design. If the local limit is 20 feet, an architect must strategically choose roof types (low-slope vs. peaked) and foundation methods (slab vs. raised) to gain enough vertical space for two full, code-compliant, and highly rentable floors. We have even been creative to get two story structures under the height limit but submerging the ground level of an ADU a few feed below the grade of a yard. These types of creative solutions are why hiring an experienced company like Modern ADU Plans can lead to the best option for your situation.

• Engineering Value: When height is constrained (e.g., 16 feet), the design must shift to a single story or a structure with attic-like space, proving that the D-ADU's design must be calibrated to the specific inch of the local height code to maximize your investment return.

Design Considerations for Modern D-ADUs

The detached nature allows for maximum design flexibility and architectural excellence for both the exterior look and feel and the interior layout and function. Focus on these elements when choosing your plans or discussing a custom design:

1. Privacy and Separation: Orient windows and outdoor spaces (like decks or patios) away from the primary residence and neighboring properties to maximize tenant comfort and value.

2. Making a Small Home Feel Larger: use views, access to narture, sliding doors, open layouts, and heigh ceilings to make the smaller spaces of an ADU feel larger.

3. Curb Appeal: The D-ADU should complement the main house but embrace a modern, efficient design. You don’t want it to look like a fake imitation of a historic style. The ADU design should reflect the time it was built. Focus on large windows, sustainable materials, smart siding, and clean rooflines. Look for design elements that can enhance the feel of the ADU through trellises, wood screens, planters, and other design elements that make the home feel welcoming.

4. Accessibility: Consider future use. Incorporating zero-step entryways and barrier-free bathroom layouts significantly increases the value and flexibility of the unit for aging-in-place. Whether you are building this now for an aging family member, or you plan to move into the ADU in the future when you are getting older, thinking about accessibility during the design can make your ADU ready for any future use. Plus it could demand higher rent, and be worth more as an investment.

III. Step-by-Step Construction: The Detached ADU Process

The process for building a Detached ADU (D-ADU) is structurally akin to building a small custom home, demanding the same professional rigor, design documents, engineering precision, and schedule discipline. Unlike minor renovations, a D-ADU rbegins with ground-up site work—a phase that is frequently underestimated. Mastering the sequence of these steps is essential, as permits, inspections, and contractor coordination depend on adherence to this order. Knowing the sequence not only helps you manage contractors and timelines but also empowers you to anticipate critical milestones like utility connections and final Certificate of Occupancy, transforming you from a passive homeowner into an informed project manager.

Phase 1: Pre-Construction & Site Preparation

• Demolition & Site Clearing: Clearing the area, removing existing sheds, and performing any necessary tree removal.

• Permitting: Final sign-off on construction documents.

• Excavation & Foundation: Digging utility trenches and pouring the foundation (a critical first step that must pass inspection).

Phase 2: Shell Construction (Framing and Weatherproofing)

• Framing: Erecting the walls, floor, and roof structure.

• Rough-Ins: Installing electrical wiring, plumbing pipes, and HVAC ductwork before the drywall goes up. This includes running the trenches to the main house.

• Exterior Finishes: Installing roofing, windows, exterior siding, and weather barriers to make the structure water-tight.

Phase 3: Interior Finishes & Final Inspection

• Insulation & Drywall: Completing the walls and ceiling.

• Interior Finishes: Installing flooring, cabinetry, interior doors, and plumbing/lighting fixtures.

• Landscaping & Connections: Final grading, connecting utilities, and completing any required fire access paths.

• Final Inspection: Receiving the Certificate of Occupancy (COO), which allows the unit to be legally rented or lived in.

GET STARTED: Ready to find your build partner? Read our guide: Your Guide to Hiring a General Contractor for Your ADU Project.

IV. The Best Detached ADU Plans for Any Backyard

Choosing a pre-designed plan dramatically cuts down on the design timeline and cost compared to a fully custom build. Our plans are specifically engineered to meet modern code requirements while maximizing living space.

Here are a few of our most popular detached ADU plans, perfect for various needs and lot sizes:

Sale

The Backyard Oasis ADU

Sale Price: $1,499.00 Original Price: $1,999.00

Purchase

Sale

The Screen ADU

Sale Price: $1,499.00 Original Price: $1,999.00

Purchase

Sale

The Overhang ADU

Sale Price: $1,499.00 Original Price: $1,999.00

Purchase

Ready to Realize Your Backyard’s Potential?

Browse our full collection of architect-designed detached ADU plans and find the perfect fit for your property and investment goals.

5 Modern ADU Floor Plans That Work on Almost Any Property

If you're a homeowner looking to increase your property's value, create rental income, or provide a flexible living space, an ADU (Accessory Dwelling Unit) might be the smartest investment you can make.

In fact, recent research shows that adding an ADU can increase your property value by 20% to 30%. And depending on your location, renting one out could bring in $1,500 to $4,000 per month in rental income. That’s why more cities across the U.S. are updating zoning laws to encourage detached ADU development. These small homes are solving big problems: housing affordability, aging in place, and sustainable urban growth.

But the key to a successful ADU project? Choosing the right floor plan from the start.

In this guide, we're sharing five pre-designed, modern detached ADU layouts that are functional, affordable, and work well on a wide range of properties. Whether you're looking for a compact studio or a more spacious two-bedroom, these floor plans are optimized for how people live—and how cities approve construction.

Let’s dive in.

Sale

The Cabin

Sale Price: $1,499.00 Original Price: $1,799.00

Purchase

1. The Modern Studio ADU

A studio ADU is the perfect entry point. These small, efficient homes are typically between 400 and 500 square feet and combine all essential living functions, sleeping, cooking, and bathing, into one thoughtfully designed space. They are pretty affordable and simple to build.

🛠 Ideal size: ~350–500 sq ft
🏡 Best for: Rentals, guest suites, short-term stays, offices

Why this floor plan works:

• Small footprint = lower cost and faster permitting

• Can fit almost anywhere on your lot

• Low utility and maintenance costs

• Feels modern and spacious with open-concept design

These are especially popular in cities like Los Angeles, Seattle, and Portland, where lot sizes can be tight, and simplicity speeds up approval. They often have a good return on investment as they are the simplest, most cost-effective ADU to build, but you can still get decent rent in high-demand cities or neighborhoods.

Sale

The Backyard Oasis ADU

Sale Price: $1,499.00 Original Price: $1,999.00

Purchase

2. The One-Bedroom ADU

The one-bedroom ADU strikes the perfect balance: it offers privacy and separation between the sleeping and living areas, while still remaining compact and affordable. They can demand a bit higher rent, but are still pretty simple and affordable to build. In fact, our most popular design - The Backyard Oasis ADU - is a one-bedroom that blends a simple plan with a modern look and feel. It is a great fit for almost any backyard and makes a perfect rental unit or short-term AirBnB rental.

🛠 Ideal size: ~500–700 sq ft
🏡 Best for: Long-term rentals, parents, adult kids, couples without kids

Why this floor plan works:

• Flexible layout options (L-shape, linear, or stacked)

• Large enough for full-time living, small enough to remain affordable

• Increases your property’s livable space without sacrificing your backyard

• Popular with renters looking for independent housing

These ADUs make a great case for permanent housing, particularly in neighborhoods where the cost of construction or living space is high.

Sale

The Screen ADU

Sale Price: $1,499.00 Original Price: $1,999.00

Purchase

3. The Two-Bedroom ADU

Two-bedroom ADUs offer the most versatility. With more square footage, these units can comfortably house families, multigenerational households, or live-in caregivers. They can demand higher rent as they could house a family, or you could rent each bedroom separately or to roommates.

🛠 Ideal size: ~700–900+ sq ft
🏡 Best for: Families, aging parents with caregivers, higher-value rentals

Why this floor plan works:

• More privacy and separation between rooms

• Feels like a full standalone house

• Excellent for long-term use or home + office setups

• Maximizes ROI through flexible occupancy options

If you have the space and budget, a two-bedroom layout is a future-proof option, whether you use it yourself or rent it out. It gives the most flexibility and does a great job at balancing private bedrooms with enough space for very nice living and kitchen areas.

Sale

The Overhang ADU

Sale Price: $1,499.00 Original Price: $1,999.00

Purchase

4. The ADU Over Garage

Want to add living space without sacrificing your yard? An ADU built over a garage is a smart way to go vertical, especially in urban areas where square footage is tight. There is often a tug of war between building an ADU and accommodating off-street parking. Although ADUs provide much more value than a parking space, many families want both. This is the perfect balance. You get an nice ADU while still maintaining parking or better yet, space for hobbies like a workshop.

🛠 Ideal size: Varies (~400–800 sq ft above a 1 or 2-car garage)
🏡 Best for: Urban homes, privacy-focused users, dual-purpose builds

Why this floor plan works:

• Efficient use of vertical space

• Offers elevated views and clear separation from the main house

• Combines storage/parking with livable space

• Perfect for adding value without expanding the building footprint

Over-garage ADUs are ideal for lots where yard space is limited but local code allows for vertical expansion. You get bonus storage below and usable living space above. Make sure you check your local ADU regulations to find out if you can build tall enough to comfortably accommodate a garage with an ADU above. One other thing to consider with these ADUs, is that they won’t be accessible. They are probably not a great fit for aging-in-place or housing people who have physical challenges climbing stairs. Which leads us to our last ADU type.

Sale

The Japandi ADU

Sale Price: $1,499.00 Original Price: $1,999.00

Purchase

5. The Accessible, Aging-in-Place ADU

Designed with mobility and long-term use in mind, accessible ADUs are increasingly in demand—not just for aging parents, but for anyone who values comfort, safety, and inclusive design. Because these work for people with all physical abilities, we often recommend starting with accessible, barrier-free ADU designs for everyone. It often doesn’t cost more and gives you flexibility. If I were building an ADU for myself, I’d design it to be barrier-free design.

🛠 Ideal size: ~500–800 sq ft
🏡 Best for: Elderly family, mobility-impaired users, future-proofing

Why this floor plan works:

• Single-level layout with no steps or thresholds

• Features like wide doorways, curbless showers, and open kitchens

• Can qualify for city incentives or fast-track permitting

• Keeps aging family members close while giving them independence

These ADUs provide peace of mind today, and flexibility for the future—whether for family needs or resale appeal.

The Right ADU Floor Plan Is Waiting For You

The demand for ADUs is growing rapidly across the US and Canada, and with good reason: they’re practical, sustainable, and offer real financial upside. But before you jump into permitting or construction, choosing the right floor plan will save you time, money, and headaches down the road.

Each of the five ADU floor plans above has been carefully designed to work with a wide range of properties, maximize usable space, and meet most local building codes. When you choose a pre-designed plan, you avoid the back-and-forth of custom architecture—and instead get a faster, more affordable path to building your dream ADU.

At Modern ADU Plans, we make it easy to find a design that fits your goals and your property.

ADU Zoning Rules for Columbia County, Oregon

Doing some research for a recently project had us looking up ADU regulations in Columbia County in Oregon. I’ve shared the actual code language below to make it easier for you to find the information you need. In general, this is one of the more restrictive ADU codes we have found . It sounds like the people who wrote this code either don’t want ADUs, or are listening to NIMBYs or others who are anti-ADU.

The actual zoning language:

224 Accessory Dwelling Units

1. One accessory dwelling unit is allowed in conjunction with a detached single-family dwelling on a lot zoned for single-family development within an Urban Growth Boundary (UGB) of a city. UGB areas have the following residential zoning districts: Single-Family Residential (R-10), Single-Family & Two-Family Residential (R-7), and Rural Residential (RR-5 and RR-2).

2. An ADU shall contain a kitchen, bathroom and a living/sleeping area that is completely independent of the primary dwelling. Recreational vehicles are not allowed as an accessory dwelling unit. Creation of a new Accessory Dwelling Unit may be accomplished through any of the following methods:

   1. A. Attached to the primary dwelling by converting a single-family dwelling’s existing living area, attic, basement or garage;

   2. B. Attached to the primary dwelling by adding floor area to the existing single-family dwelling;

   3. C. Constructing a detached accessory dwelling unit on the developed site including siting of a manufactured dwelling;

   4. D. Converting an accessory building, or portion thereof, to an accessory dwelling unit; or,

   5. E. Constructing a new dwelling with an internal accessory dwelling unit and, ~ 24 ~

   6. F. Constructing a new dwelling and converting the existing dwelling to a detached ADU, provided both dwellings meet the minimum zoning requirements.

3. The County will require the proposed Accessory Dwelling Unit to comply with the Gross Habitable Floor Area, and Owner Occupancy requirements as imposed by the City for the unincorporated portion of the City’s Urban Growth Boundary Area.

4. Domestic Water:
   Documentation shall be submitted to LDS that the ADU can be served by an existing public or community water district or by a private well that has been recorded with the State of Oregon Water Resources Department. LDS shall also require a Will Serve letter from the community/city water purveyor verifying the ADU can utilize the water system.

5. Sewage Disposal:
   The County Sanitarian shall review and approve the proposed method of onsite sewage disposal for the ADU for compliance with the applicable provisions in the Oregon Administrative Rules (OAR) 340-071-0205 for existing septic systems. If the ADU will utilize community sewer, documentation shall be submitted to the County that the affected city will provide sewer service.

6. Access:
   The road access to all ADUs shall be reviewed and approved by the County Public Works Department and the affected city for consistency with the applicable provisions of the County Road Standards Ordinance and the Urban Growth Area Management Agreements between the affected city and Columbia County.

7. Siting Requirements/Standards:
   The proposed ADU must comply with the underlying zone R-10, R-7, RR-5 and/or RR-2 Zones’ minimum yard setback requirements for primary dwellings. Height limitations and lot or parcel coverage requirements shall be the same as the underlying zone.

8. On Site Parking:
   The ADU shall provide one additional on-site parking space if the primary dwelling has less than three available on-site parking spaces (inclusive of garage and driveway).

9. Location of Entrances:
   For an attached ADU only one entrance to the residence may be located on the front of the dwelling facing the street, unless the primary dwelling contained additional door entrances before its conversion to an ADU. An exception is entrances that do not have access from the ground such as entrances from balconies or decks.

10. Exterior Design and Appearance:
    ADUs shall maintain consistency with the primary dwelling. For an ADU that is created by an adding floor area to the existing primary dwelling, the ADU shall have the same siding and roofing materials and exterior paint colors as the primary dwelling. For a detached ADU the County will require compliance with clear and objective design and appearance regulations adopted by the City where the UGB is located. ~ 25 ~

11. Divisions of Property:
    The division of a property containing an ADU shall comply with the minimum and applicable provisions of Zoning District and Subdivision and Partitioning Ordinance. Establishing a new ADU shall not allow the further division of RR-5 and RR-2 properties provided for in Sections 606 and 627 of the County’s Zoning Ordinance.

12. Alteration:
    If an existing authorized detached accessory structure, or portion thereof, is converted into an ADU, it is exempt from the minimum setback standards for primary dwellings. Any floor area that is added to this structure must not increase the setback non-conformity. Proposed expansions are not eligible to be approved with a Variance to the setback standards for single-family development.

13. Existing Non-conforming ADU:
    An existing, non-conforming second dwelling on a lot or parcel in any residential zone permitted by this section may be determined to be a conforming ADU through an approval process that includes the following:

    1. A. All necessary building permits and occupancy authorization is obtained to assure the ADU complies with the applicable fire, life & safety and building codes per the Oregon Residential Specialty Code and

    2. B. The ADU complies with other requirements of this section, such as size, floor area, water, sewerage, entry and access.

Commentary:

Their decision to impose style restrictions is terrible policy. In fact, I believe style restrictions should be illegal. It has nothing to do with protecting the health, safety, or welfare of the public and has no place in codes.

Further, the requirement to create an additional parking space is another sign that they don’t actually want to make building ADUs easy. In fact, this is an overreach by dictating how you can use your private property. Parking requirements make housing more expensive, directly lead to more traffic congestion, and have nothing to do with the health, safety, or wellfare of the public. Again, these types of regulations should be outlawed on the national level.

The only positive thing I can say about these ADU regulations is they at least allow ADUs. Other than that, this is an example of how to write a terrible ADU code that makes them harder to build and more expensive.

Maximize the ROI On Your Property With Our Free ADU Investment Proforma Worksheet

If you are considering investing in an Accessory Dwelling Unit (ADU) to maximize the value of your property or generate rental income, you have found the right place. Homeowners like you are an integral part of addressing our housing issues, while ADUs can also be a huge part of building generational wealth. Modern ADU Plans has developed free resources to help you make informed decisions about your ADU project. Along with our ADU Budget Worksheet, we highly recommend downloading our comprehensive ADU Investment Proforma Worksheet.

But First, Why Choose To Build An ADU?

ADUs are on the rise across the US and Canada for good reason. Accessory Dwelling Units help homeowners increase their property value, generate rental income, or provide a space for family members and guests. Many of our cleints even build an ADU for themselves to move into so they can rent out the larger main house. This is especially popular if their kids have grown up and moved off to college.

Not only are ADUs great for homeowners like you, they are also great for our communities. Towns and Cities across the country are facing housing shortages as we have underbuilt housing for decades now. We see this issue manifest in the homeless crisis we see and hear about on the news and in our towns. ADUs can be a great way to add new housing options in an affordable way without leading to sprawl. They are a sustainable way to increase housing supply within our communities.

These versatile structures are cost-effective, environmentally friendly, and can significantly boost the overall value of your property while improving your neighborhood.

Make Informed ADU Investment Decisions

Like investing in other real estate assets, building an ADU requires careful planning and consideration of various factors such as construction costs, potential rental income, financing options, and return on investment. Our free ADU Investment Proforma Worksheet is designed by experts in the field to help you analyze these crucial aspects and make sound financial decisions.

Although small in size, building an ADU is still a significant investment. It takes hundreds of thousands of dollars to build a quality ADU and we want you to spend your money wisely. Specifically, we want you to have a positive return on this investment. You should see cashflow on a monthly basis through rental income as well as an increase in your property value if you ever decide to sell the property in the future. This is why we advise our clients to work through a project proforma and develop a comprehensive project budget at the outset of an ADU project.

The Power of Data-driven Planning For Your ADU

Our worksheet provides a clear layout for inputting your project specifics, including construction costs, estimated rental income, financing terms, and ongoing expenses. By utilizing this powerful tool, you can project your potential cash flow, calculate your return on investment, and assess the financial viability of your ADU project.

What you need to do is some basic research on your local market. Input the going rates for similar sized rental units in your area, research local construction costs, and contact your bank for information on financing options. We can also assit you with answering these questions and filling out the proforma if you need help.

How to Get Your Free ADU Investment Proforma Worksheet

To access this valuable resource and kickstart your ADU investment journey, simply download our free ADU Investment Proforma Worksheet using the short form to the right. Empower yourself with the knowledge and tools needed to make informed decisions and maximize the potential of your property by planning for your new Accessory Dwelling Unit.

Don't miss out on this opportunity to take control of your financial future with an ADU investment. Download our free worksheet today and embark on your path to property enhancement and financial success!

Disclaimer: The information provided in the ADU Investment Proforma Worksheet is for general informational purposes only and should not be considered financial advice or legal advice. Please consult with a qualified professional for personalized guidance tailored to your specific situation.

Invest wisely, invest in ADUs with Modern ADU Plans.

Your ADU Proforma worksheet is complete and you are ready for the next steps?

There are a few ways you can move your project forward after you work through the proforma and make the decision to proceed with building an ADU.

You can hire a designer to help develop a custom designed ADU, purchase a pre-designed ADU plan, or talk to an ADU expert to discuss your ideas and develop a plan. Modern ADU Plans offers all of these options to help homeowners like you achieve your ADU goals.

There are three convenient buttons to the right, each offering you a way to take the next step towards your ADU.

Maximizing Your ADU Budget: Download Our Free ADU Budget Worksheet Today

If you are considering building an Accessory Dwelling Unit (ADU) but feeling overwhelmed by the costs involved, we sympathize. ADUs are significant investments even though they are small houses. There is also a lot of misleading information out there on ADU Facebook Groups, ADU blogs, and other sources. Budgeting for an ADU project can be a daunting task, and can get complicated, which is why we have created a comprehensive ADU Budget Worksheet to help you plan effectively and maximize your budget.

Why You Need an ADU Budget Worksheet

Your ADU project's budget is crucial to ensure that you stay on track and avoid financial surprises along the way. Planning early and accurately can help you save costs and avoid mistakes on your ADU build. Our ADU Budget Worksheet is designed to assist you in estimating costs accurately, identifying potential expenses, and helping you make informed decisions throughout the construction process. It is a guide that you can use early on in the planning process, but also set up to help you track the actual costs and compare them against your budget throughout the ADU design and construction process.

What Does Our ADU Budget Worksheet Offer?

Our free ADU Budget Worksheet includes detailed sections for all aspects of your ADU project budget, such as:

• Construction Costs: Estimate expenses for materials, labor, permits, and more.

• Design and Planning Fees: Include costs for architectural plans, engineering, and other design-related expenses.

• Utility Connections: Budget for water, electricity, and gas connections.

• Interior Finishes: Plan for flooring, fixtures, appliances, and other interior design elements.

• Exterior Finishes: Estimate costs for siding, roofing, landscaping, and other exterior finishes.

• Contingency Fund: Allocate a percentage of your budget for unforeseen expenses.

How to Download Our Free ADU Budget Worksheet

Getting your hands on our ADU Budget Worksheet is easy! Simply click the download link to the right to access this essential tool for your ADU project. Take the first step towards a well-planned and budget-friendly ADU construction process today.

Don't let financial concerns hold you back from realizing your ADU dream. Download our free ADU Budget Worksheet now and pave the way for a successful and cost-effective ADU project. Download now and start building your dream ADU with confidence!

Remember, proper budgeting is the key to a stress-free ADU construction experience. Let our ADU Budget Worksheet be your guide as you embark on this exciting journey.

Your ADU budget worksheet is filled out and you are ready for the next steps?

There are a few ways you can move your project forward after you work through the budget. You can hire a designer to help develop a custom designed ADU, purchase a pre-designed ADU plan, or talk to an ADU expert to discuss your ideas and develop a plan. Luckily Modern ADU Plans offers all of these options to help homeowners like you achieve your ADU goals.

There are three convenient buttons on the right side of this blog, each one offering you a way to take the next step towards your ADU.

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Next Steps for your ADU Project:

Video: 5 Things to know before building your ADU

Southern Californians are racing to build accessory dwelling units — or ADUs — small, fully equipped homes on the same lot as a larger house. But building an ADU can be complicated and expensive. This video discusses 5 things you should know as you embark on building an ADU on your property.

Read the full story from the LA Times: You Do ADU, Part 1: Thousands of Californians are building ADUs. Should you?

California ADU Regulations - 2024

Navigating the regulations that affect new ADU projects can be daunting. Each state, county, city or town has their own rules and regulations that affect these projects. However, some states are passing state-wide rules to aim to unify some of the restrictions and make ADU development easier. California is one of the states leading this charge as they aim to promote ADUs as an important part of addressing housing affordability challenges.

With the goal of making ADUs easier to build, California has been passing some great laws that have drastically changed the ADU rules. There are some big changes even from last year. In the article below we will discuss some of the updated rules. But first, let’s start with the basics.

What is an ADU?

ADU is an acronym for Accessory Dwelling Unit. Often called other names like casita, laneway suite, garden suite, granny flat, or even guest house, ADUs are secondary homes built on a property, which are accessory to the primary structure. Unlike tiny houses on wheels, ADUs are full houses and include permanent foundations, separate entrances from the main house, fully functional kitchens, full bathroom, space for sleeping (either a bedroom or space for a bed if the unit is a studio), plus full utilities (water, sewer, and electricity).

ADUs are typically built as rental units, houses for extended families, or homes for downsizing and aging-in-place. In many places they can also be used as short-term rentals like for AirBnB or VRBO, although some towns and cities prohibit this use as they want ADUs to be used as permanent housing.

California Regulation Changes for 2024

Where there once was a tapestry of different rules and regulations across the state, California has been working on passing ADU laws that are applied statewide. Government officials have seen the challenges of having so many different rules and restrictions, thus they have been working to pass laws that override local restrictions that were used to prohibit or significantly hinder the ability for some homeowners to add ADUs to their properties. Because ADUs provide a lot of benefits to both individual property owners as well as society at large, passing statewide regulations that are easy to meet is helping people build enough ADUs to significantly increase the housing supply across the state.

Owner Occupancy on the Property

Owners are no longer required to live on the property if they want to build an ADU and rent it out according to AB 976. Property owners can now build ADUs and rent out both the main house and the new ADU. California has removed this requirement statewide, meaning no local jurisdiction can make this a requirement. This is a win for those looking to add ADUs to properties they currently own but are renting out. We believe ADUs are great investment opportunities and this doubles down on that belief.

ADUs can be sold separately as Condos

We absolutely love this change and think it is a true game changer for ADUs. It is something we hope spreads nation-wide as a way to make more affordable starter homes available for purchase.

Basically, it is now possible to build a new ADU on a property, and then condoize all of the homes on the property to be able to sell them separately. Meaning, you can now develop ADUs as a for-sale product rather than just as a rental unit. This is great if you want to build an ADU as an investment but want to get your money out of the project relatively quickly.

In markets where housing prices are quite high, you could see situations where you may build an ADU for say $300,000, condoize the property, and then sell off the ADU for say $450,000. In just a year or two you could see a 50% return on your investment. Plus you are creating a home that can be purchased for a very reasonable cost compared to many homes on the market.

ADU Types that are now allowed in California

All residential properties are eligible to add an ADU. And depending on the size of the property you could build up to 3 ADUs on your property - one Junior ADU (JADU), one attached ADU, and one Detached ADU (DADU). You can also convert existing structures like garages into ADUs.

ADU Size regulations

There are different maximum size limitations based on the property and layout of the ADU. In all cases you should be able to build an ADU up to 800sf. Individual jurisdictions can’t limit ADUs to below that size but can pass local laws increasing the maximum size an ADU can be. The state has passed laws that if no maximum size is defined then the maximum size is automatically set at 1,200sf for detached ADUs. If you are doing an attached ADU you can build up to 50% of the floor area of the main house or 800sf, whichever is larger.

Furthermore, if you are converting an existing structure you don’t have to abide by ADU size limitations as long as you aren’t expanding the size of the structure. If you stay within the existing footprint you can have an ADU of any side. This is great news if you are converting a large garage, basement, or other existing space into an ADU

Property Setbacks for ADUs

Most properties have setback requirements for buildings that prevent you from building right up to the property lines. I am very much against property setbacks as they prevent us from building some of the best housing types, like attached row houses. Side setbacks especially should be illegal nation-wide. But that is a battle for another day.

For ADUs in California side and rear setbacks are set at 4’ unless a local jurisdiction passes a law reducing that. Places like San Diego have stated that there is a 0ft side and rear setback for ADUs!

The front setbacks are a bit more flexible and can still be set by each jurisdiction as long as it doesn’t hinder the property owner’s ability to build an ADU up to 800sf.

ADU Height Limits

Height limits get a bit more complicated as it depends on location of the property, existing structures, and the type of ADU. The following rules apply:

• 16 ft height limit is the minimum for every ADU in California under any circumstance. Local jurisdictions can’t enforce a lower height limit. This most likely leads to a single story ADU although we have found some creative workarounds to get two-story ADUs within a 16’ height limit. Curious? Contact us for more information.

• 18 ft heights are allowed if an ADU is within 1/2 mile walking distance from public transit or if the property already has a two story tall multi-family dwelling. 18’ tall ADUs can definitely be a two story structure.

• 25 ft height limits are imposed if the ADU is going to be attached to the main residence. Even if the main house is taller, the ADU can only be 25’ tall.

Parking Requirements for ADUs

This is another area where we disagree with many of the regulations. Under no circumstances should parking be required on any property. It should be up to the property owner to decide if they want to build parking. Parking minimums are the dumbest laws and directly lead to more expensive housing and terrible environmental impacts. Parking requirements should be abolished nation-wide.

Alas, here are the rules:

• Off-street parking is required for ADUs in most circumstances.

• Exceptions:

  • If an ADU is within 1/2 mile walking distance from public transit

  • If the ADU is within a historical district

  • If the ADU is a conversion of existing space (like a basement or garage)

  • If the ADU is located within one block of a car-share vehicle

  • On street parking permits are required in your neighborhood but aren’t offered to the occupant of the ADU

• If you are converting a garage into an ADU, you are not required to replace the lost parking space.

CalHFA ADU Grant Availability

The CalHFA ADU Grant provided up to $40,000 towards the soft costs of building an ADU (soft costs are things like design, permitting fees, etc.). It was so popular that the latest allotment of $25 million committed to the program was claimed in just a few days. Thus no more funds are available as of the start of 2024.

Considering the popularity of the program and the continued need for new housing there is a good chance that it will be refunded in the near future.

Fire Sprinkler Requirements for ADUs

Fire sprinklers aren’t required except in a few circumstances. If they are required in the main house then they are also required in the ADU. Also, if the ADU is built far enough away from road or driveway access a sprinkler system may be required. This is due to access to the structure by the fire department and access for their trucks combined with length of fire hoses. If your ADU will be located more than say 150’ away from the street you may need to install sprinklers. Contact your local building department to verify the specifics of your project.

ADUs are now allowed on multi-family properties

All multi-family properties are now eligible to have ADUs. In fact, you can add at least one ADU by converting existing space in the building and you can add up to two additional detached ADUs. It gets even better. If the multi-family building has more than 8 units, you can add up to 25% of the number of units in the existing building. Example: if you have a 12 unit apartment building you can add up to 3 ADus (25% of the existing units).

Solar Panel Requirements for ADUs

When building a detached ADU it is required that you have solar panels on either the ADU or the main house. However, there are some exceptions for prefab ADUs or Modular ADUs. There aren’t solar requirements for basement ADUs, or JADUs.

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Ready to start your ADU Project?

At Modern ADU Plans are here to help you achieve your goals and have a successful ADU project. Head over to our ADU store to find a beautiful ADU that meets your needs, or contact us if you are considering a custom designed ADU solution. We also offer some free resources on this website and consultations if you want to meet with an ADU design expert to ask questions.

What Makes The Best ADU Design?

The Accessory Dwelling Unit (ADU) has emerged as a transformative force in modern housing, offering homeowners opportunities for additional income, flexible living space, and even multigenerational living. But amidst the excitement, a crucial question arises: what makes the best ADU design?

There's no one-size-fits-all answer, as the ideal ADU blends seamlessly with the characteristics of your property, your project budget, and the intended use of the ADU. However, certain key principles guide the creation of exceptional ADUs:

1. Functionality Reigns Supreme:

Start by defining your vision. Will the ADU serve as a rental unit, home office, in-law suite, or guest quarters? Each purpose demands distinct functionalities. Prioritize essential features like the number of bedrooms and bathrooms, size and layout of kitchens and living areas, carefully considering occupant needs and space limitations. Utilize space-saving solutions like built-in storage, convertible furniture, and open floor plans to maximize every square foot.

2. Embrace the Power of Design Flexibility:

Don't be confined by conventional layouts. Explore various ADU plan options online, including pre-designed blueprints or customizable ADU floor plan templates. These resources offer a springboard for inspiration, allowing you to adapt and tailor the design to your specific needs. Remember, flexibility doesn't compromise style. Look for plans that integrate with your personal style and taste, or your existing home's architectural style, creating a cohesive aesthetic.

3. Invest in Sustainability:

A well-designed ADU is not only functional and stylish, but also environmentally conscious. Consider incorporating energy-efficient features like solar panels, water-saving fixtures, low-energy lighting and other systems, and recycled and locally sourced materials when possible. These choices not only benefit the environment, but also reduce your long-term operational costs. Remember, sustainable design is an investment in your future and the planet's.

4. Let Natural Light Flow:

In any living space, natural light is essential for well-being and creating a sense of spaciousness. Opt for generous windows, skylights, and strategically placed light sources to illuminate your ADU. This design element not only enhances aesthetics, but also promotes mental and physical health. It can also reduce your electric bill.

5. Don't Neglect Outdoor Connections:

Every ADU benefits from a connection to the outdoors. Include a private patio, deck, or balcony for occupants to enjoy fresh air and natural surroundings. This outdoor space can become a haven for relaxation, entertainment, or even gardening, further expanding the living experience. With the smaller square footage of ADUs, outdoor living space can make them feel and act larger then they are.

Ready to Transform Your Vision into Reality?

While these principles provide a roadmap, crafting the perfect ADU requires expert guidance. Consider partnering with experienced architects, designers, and builders who specialize in ADU construction. Their expertise can ensure regulatory compliance, structural integrity, and aesthetic harmony, transforming your vision into a functional and beautiful reality.

Investing in an ADU is a wise decision, unlocking both personal and financial benefits. By incorporating these design principles and seeking professional guidance, you can turn your ADU into an asset that enriches your life and property for years to come.

Start your ADU journey today! Explore our comprehensive database of ADU plans and connect with qualified professionals to bring your dream to life.

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One of the most popular ADU designs on the internet is available for purchase. What makes this the best ADU design? The ADU plan is simple yet functional. The design is both modern yes practical and affordable. People love the covered outdoor space, the large windows, and the large open great room making the ADU interior design both beautiful and functional.

Case Study: the Garcia Family and Their Backyard ADU Investment

The Garcia family, located in sunny California, faced a common challenge as their family grew: the need for more space. With adult children struggling to afford the cost of purchasing a new home close to their parents, they decided to explore the idea of adding an Accessory Dwelling Unit (ADU) to their property for multi-generational living. The idea was for the parents to move into the ADU designed for barrier-free living and aging-in-place, while the younger family members moved into the main house. Little did they know, this decision would result in a great return on their investment and much more.

The Decision to Invest in an ADU

After careful consideration and research, the Garcia family made the decision to move forward with building an ADU in their backyard. They saw it as an opportunity to create additional living space for their family, and also as a potential source of rental income in the future. The flexibility and potential for a high return on investment made the idea even more attractive.

What pushed them in this direction was the incredibly high cost of purchasing a single family home in California. The cost of building a new construction detached backyard ADU was approximately half the cost of buying a new home which made this decision a no brainer for their family.

Construction and Design

The Garcia family wanted a high quality design but also were hoping to minimize the cost of the design process as well as cut down on the time a custom design would take. After researching a variety of options including hiring an architect for a custom designed ADU, purchasing a prefab ADU, or going with a pre-designed ADU plan set, they decided that starting with the pre-designed plans but then customizing their preferred plan to fit their needs was the best approach - balancing cost and quality.

They worked closely with our team of ADU professionals to adapt one of the modern ADU plans for sale. The accessory dwelling unit was designed to be a comfortable, fully functional living space complete with a kitchen, bathroom, and large bedroom that offered great views to the backyard garden.

The thoughtful ADU design was focused on barrier free living and aging-in-place perfect for their parents to move into and age gracefully.

Although it was designed for elderly residents, the high-quality design will enable the ADU to be a desirable living space for potential renters in the future. This gives the new backyard ADU the flexibility for immediate needs and long term financial return on the investment.

Return on Investment

After the completion of the ADU, the Garcia family enjoyed the immediate benefits of the additional space. Their adult child who moved into the main house, was able to afford their own home for their growing family while still being close to their parents. They also had the added benefit of child care close by. The ADU saved thousands of dollars each month compared to the rental prices in their area. It also will be a lot cheaper than having their parents move into a retirement or assisted living home in the future.

They also have a ready made rental unit in the future that they estimate would bring in between $2,000 and $3,000 dollars per month in rent if/when they decide to put it on the market. This will give the young family additional income and provide financial flexibility.

Added Property Value

The backyard ADU not only provided financial benefits but also added value to the Garcia family’s property. The increased square footage, modern design, and the versatility of having an additional living space on the property boosted the overall value of their home. Should they decide to sell in the future, the presence of the ADU could potentially attract more potential buyers and increase the resale value of their property, potentially by hundreds of thousands of dollars. Taking the tight residential real estate market in California into consideration, and they anticipate the value to continue to rise significantly over time.

Conclusion

The Garcia family's decision to invest in building a backyard ADU proved to be a wise choice and one that thousands of families are deciding to make each year. From providing much-needed space for their growing family to generating a significant return on investment through rental income and added property value, their backyard ADU has been a great success. Their story serves as an example of how an ADU can be a wise investment, providing practical and financial benefits for homeowners. If you’re considering adding an ADU to your property, the Garcia family's experience is a testament to the potential rewards that come with this decision.

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Stay tuned for more inspiring stories and useful tips on modern ADU living at Modern ADU Plans.
Thank you for the opportunity to share this story and highlight the positive impact of adding an ADU to a property.