As Accessory Dwelling Units (ADUs) grow popular, many homeowners wonder whether they can take their design to the next level—literally. One of the most common questions they ask is: Can an ADU be two stories? The short answer is yes, but there are important factors to consider before building one.
In this guide, we’ll explore the local regulations, pros and cons, and potential costs of two-story ADUs, helping you make an informed decision about your property.
Local Regulations and Zoning Laws
A few months ago, I worked with a homeowner in a bustling California neighborhood who had limited space but big ideas. Her backyard was modest in size, yet she wanted to create a multi-generational living space where her elderly parents could live comfortably and independently.
She asked me if an Accessory Dwelling Unit (ADU) could have two stories without compromising outdoor space. I reassured her that with the right planning and design, building the ADU vertically was not only possible but could be the perfect solution here.
And so, we designed a two-story ADU that gave her parents a spacious upstairs bedroom and living area. Moreover, the ground floor offered a shared kitchen and bathroom, all without taking up too much yard space.
Building a two-story ADU offers a range of architectural possibilities, and much like my client’s project, it can solve space issues while enhancing your property’s overall functionality. However, when planning to build a two-story ADU, you must understand the local regulations and zoning laws for these structures.
While state laws, particularly in California, have made it easier for homeowners to add ADUs to their properties, specific restrictions can vary between cities and counties. These regulations are designed to balance the growing demand for ADUs with the need to maintain neighborhood aesthetics, safety, and privacy.
Below are the key regulations to keep in mind when planning a two-story ADU:
Height Restrictions
Local planning departments set height restrictions to ensure that new constructions blend in with existing neighborhood architecture and don’t overpower surrounding homes. For example, in many California cities, the height limit for a single-story ADU is around 16 feet, while for two-story ADUs, the limit can range between 25 to 30 feet, depending on local rules.
Some cities may allow taller structures in exchange for larger setbacks from property lines or in specific zoning areas. It’s important to check your local city’s planning code to determine the maximum height limit for your ADU.
Additionally, if your property is located in a historic district or a neighborhood with special design guidelines, you may face stricter height limitations to preserve the area’s historical look.
Setbacks
Setbacks refer to the required distance between your ADU and property lines, streets, or other buildings. They help prevent overcrowding, protect privacy, and ensure space for emergency access.
In many areas, ADUs must be at least 4 to 5 feet away from side and rear property lines. However, a two-story ADU might need larger setbacks than a single-story unit to reduce its height impact on neighboring properties. Some cities may also have stricter setback rules if the ADU is near a main road or faces another home.
Parking Requirements
Typically, parking requirements for ADUs depend on the number of bedrooms or the size of the unit. For example, a city might require one additional parking space for each bedroom in the ADU.
However, under California’s ADU laws, if your property is within half a mile of public transit, you may not need to add extra parking, no matter the size or number of stories. Some cities have even relaxed these rules further to encourage ADU construction, reducing or removing parking requirements altogether.
Keep in mind, though, that a two-story ADU with multiple bedrooms or more living space may still face stricter parking rules if your city enforces them. In such cases, you might need to provide on-site parking or apply for exemptions.
Neighbor Considerations and Design Review
In many areas, homeowners building a two-story ADU may need to address privacy concerns for their neighbors. Since a two-story unit can rise above fences and hedges, it may overlook nearby properties, raising privacy issues.
Some municipalities may require submitting a design review or public notice to neighbors before approving a two-story ADU. In these cases, neighbors may have the chance to give feedback on the proposed design, particularly if it impacts their privacy or view. To meet these concerns and follow local rules, you might need to use frosted windows or add landscaping.
Pros and Cons of Two-Story ADUs
While two-story ADUs offer advantages in terms of space and design flexibility, they also come with certain challenges that you must carefully consider. Let’s explore the pros and cons to give you a clearer picture.
Pros
A two-story ADU can be a smart solution for many property owners. Let’s explore a few benefits of choosing a multi-level ADU for your home.
Maximizes Space on Small Lots
In areas with limited lot space, a two-story ADU lets homeowners add more living space without expanding the building’s footprint. This is especially valuable in densely populated urban or suburban neighborhoods, where backyard space is often scarce.
By building upward instead of outward, you can preserve yard space for other uses like outdoor seating, gardens, or playgrounds.
Greater Design Flexibility
With two levels, you have the flexibility to separate living areas, like placing bedrooms upstairs, and common areas, like the kitchen and living room downstairs. This setup also improves privacy for both the ADU residents and the main household.
Additionally, multi-level ADUs can be designed for multiple uses. For example, you can use the first floor as a home office, gym, or guest room, and the second floor as living spaces.
Enhanced Curb Appeal and Aesthetics
A two-story ADU can greatly improve the look of your property. With more vertical space, architects can add features like larger windows, unique roof designs, and varied exterior materials to make the ADU stand out. The taller structure allows more light inside, giving it an open and airy feel, and adds a modern, sophisticated touch.
Furthermore, the vertical design can create a dynamic look that complements the architecture of the main house. Whether you prefer a sleek, contemporary style or a more traditional design, a two-story ADU offers plenty of customization options.
Cons of Two-Story ADUs
Before deciding to move forward with a multi-level design, you need to consider the potential drawbacks of constructing a two-story ADU.
Higher Construction Costs
Multi-level structures are inherently more complex to design and build compared to single-story units. Thus, they come with higher costs.
Factors that contribute to the higher cost include:
- Foundation Reinforcement: A two-story building needs a stronger foundation to support the extra weight of a second floor.
- Staircases: Adding staircases increases construction costs and takes up more interior space.
- Framing and Structural Support: Taller walls and more complex framing add to the cost of building a multi-level structure.
- Utilities: Plumbing, electrical, and HVAC systems need to be extended across two levels, which may involve more materials and labor.
While the increased costs can be offset by the extra square footage and potential rental income, it’s essential to factor them into your overall budget.
Potential Zoning and Height Restrictions
Building a two-story ADU can be tricky due to local zoning rules and height restrictions. Many cities have specific limits on ADU height, especially in areas where preserving sightlines and reducing the impact on neighbors is important. If your design goes over these limits, you may need a variance, which can slow down the approval process and add extra steps.
It’s important to check with local planning departments and work with experienced builders to make sure your design follows these rules from the start.
Accessibility Challenges
While a two-story ADU offers many benefits, it can be challenging for people with mobility issues. Stairs are a key part of a multi-level design. But for elderly residents or those with disabilities, they can be a major obstacle. If you’re planning to use the ADU for aging parents or as a future retirement home, accessibility should be a top priority.
While you can add features like elevators or chair lifts to improve access, these options can raise construction costs and take up space. If you want to future-proof your property, a single-story ADU might be a more practical choice.
Mitigating Costs and Finding a Balance
While the cost of building a two-story ADU can be higher, there are ways to mitigate some of these expenses.
Efficient Design Choices
A compact, well-planned floor layout can lower material and labor costs without sacrificing functionality. Aligning utilities like plumbing and electrical systems vertically between the two floors can simplify installation and reduce expenses.
Moreover, you can choose a simple staircase design, like a spiral or straight-run staircase, to save both space and money. Also, use open-plan layouts with fewer interior walls to make the space feel larger while lowering construction costs.
Choosing Cost-Effective Materials
While high-end finishes and materials can elevate the look of your ADU, they also increase the budget. Instead, choose durable, mid-range materials that offer both quality and longevity without breaking the bank. For example, you could use engineered wood flooring instead of hardwood or fiber cement siding to save money while still achieving an attractive finish.
You can also reduce costs by using prefabricated or modular components. These are made off-site and assembled on-site, cutting labor time and potentially lowering construction costs. While modular designs may limit customization, they can still be tailored to your needs and provide significant savings.
FAQs
1. Do two-story ADUs take longer to build than single-story units?
Yes, two-story ADUs typically take longer to build due to the more complex construction process, including staircases and reinforced foundations. On average, it can take anywhere from 8 to 12 months from planning to completion.
2. Can a two-story ADU be built on a sloped lot?
Yes, a two-story ADU can be built on a sloped lot, but it may require additional engineering and foundation work. This can increase the cost and complexity of the project.
3. Do I need a separate entrance for each floor in a two-story ADU?
While you don’t need to have separate entrances for each floor, some homeowners opt for it if they plan to rent out each floor independently. This can offer greater privacy for occupants.
Conclusion
While an ADU can be two stories, it requires thoughtful planning, attention to local zoning laws, and careful consideration of costs. A multi-level ADU can maximize living space and enhance privacy, but it also increases construction expenses and potential regulatory challenges.
If you’re considering building a two-story ADU but don’t know how to navigate the zoning challenges, we at GoldenADU can help! Our team can offer you expert advice on everything from design to local regulations. Just contact us at 213-693-2405 to schedule a free consultation.
