What Does ADU Stand for in Real Estate?

An ADU stands for an accessory dwelling unit, which is a secondary living space built on the land you own and where your primary residence exists. Located on the same property, accessory dwelling units (ADUs) can provide shelter for family members, generate rental income, serve as guest house facilities, or become your investment in a future resale venture.

Where you place your accessory dwelling unit (ADU) holds equal importance to choosing the exact layout or details of the design. When you build an ADU, abiding by building codes and regulations is crucial.

Let’s discuss the meaning of ADU, its benefits, and essential considerations for ADU building!

Accessory Dwelling Unit Purposes

Accessory dwelling units have versatile designs and features. They differ in size, configuration, way of construction, and many other aspects. So, it’s important for property owners to understand in advance why they need an auxiliary residential unit.

Accessory dwelling units (ADUs) serve a variety of purposes, including:

• Providing independent living space

Do you have an elderly family member who needs a small home with a separate entrance? Or maybe your adult children don’t fit into the existing single-family home? A backyard cottage on the same lot can accommodate your extended family members at a convenient distance.

• Separate unit for guests

An ADU home is also a great solution if you frequently house guests. If the main house becomes too crowded with each family reunion, build a nice, tiny ADU house on the same grounds.

• Source of passive income

Of course, ADUs have quite high upfront costs. But who hasn’t dreamed of easily covering monthly expenses? Besides offering permanent living space, ADUs can serve as rentals and bring you up to $2,000 per month.

• Increasing property value

By building an accessory dwelling unit, you improve the overall utility of your property. So when you need to sell your land with the primary residence and an ADU, its real estate market price may be way higher than the price you initially paid for it.

• Secondary dwelling unit for work and hobbies

Create additional living spaces for storing items, working remotely, or enjoying your leisure time. ADUs can be home offices, home theaters and playrooms, photography studios, greenhouses for cultivating rare plants, and many more.

Whether you’re looking for extra living space for a granny flat, an additional income source, or selling it together with your existing property in the future, ADUs are multifaceted affordable housing options that can significantly enhance the usability and versatility of your property.

Accessory Dwelling Unit (ADU) Types

ADU projects encompass planning ADUs, designing their layout, acquiring permits, preparing the site, and the ADU construction process itself. When you plan your ADU project, you either choose between several pre-designed ADU options or do the architecture from scratch.

In most cases, you’ll eventually opt for one of these common ADU types:

• Detached Accessory Dwelling Units (ADUs)

Detached units are self-sufficient, standalone residential units akin to your main house. The only difference is their size. They offer the same amenities as big homes: a sleeping area, a food preparation area, a bathroom, and a living space. They usually have their own utility connections independent of their primary residence.

• Attached ADUs

Unlike detached ADUs, attached ADUs adjoin the primary house. If a detached ADU has separate utilities, an attached ADU may share utility connections and some amenities with the existing home, which makes it a cheaper option.

• Garage Conversions

In contrast to newly constructed ADUs, a garage conversion plan suggests utilizing an existing structure like your unused detached garage. Similarly, owners of carriage houses can have their units converted into ADUs. This small dwelling will have a pre-built frame, requiring only upgrades to meet residential space standards.

• Internal ADUs

In addition to autonomous ADUs, there’s one more type that is very similar: a home extension. If you have an underused attic, basement, or spare bedroom, you can create an internal ADU within the framework of your main house’s existing space. For example, a small but functional basement apartment.

• JADUs

Junior ADUs are simply small living spaces that come into existence as a result of conversion. Some garage conversion ADUs fall under the notion of JADU. JADUs can be no more than 500 sq. ft.

When selecting the type of ADU, consider the zoning laws and local ordinances that apply to each particular type of accessory dwelling unit (ADU). After all, ADU laws play a key role in determining the specific building requirements, amounts of fees, complexity of the permitting process, and overall feasibility of your ADU project.

Accessory Dwelling Unit Setbacks

No matter the square footage, an ADU can only occupy a certain zone within your plot. The borders of your land have the name “property lines.” And you can only position your accessory unit at a defined distance from the property lines.

Local jurisdiction rules establish the particular values of these setbacks. In California, you can place your ADU four ft. from the side and rear property lines. Some jurisdictions even allow zero setbacks. However, many ADU builders recommend building an ADU six or more ft. away from the property lines to ensure compliance with not only setback requirements but also fire safety rules.

There are reasons why it’s better to stick to a 6-foot setback:

1. Simpler way to the construction site;
2. Preventing expensive fire-rated buildings;
3. Ensuring increased functional area and storage capacity.

Keep in mind that if your ADU has a garage space attached to it, the garage space must abide by its own setback requirements. These requirements are typically 10 to 15 ft. for the rear line and 5 to 7 ft. for the side line. Thus, if two constructions share a wall, it makes sense to plan the ADU in such a way that the garage takes its proper place.

ADU Setbacks: Why Do They Exist?

Why do we need regulations regarding setbacks for ADUs? There are several key reasons:

• Safety. By keeping a minimum distance between the ADU and property lines or other objects on your land, we can reduce the risk of fire spreading around. It also eases access to emergency services in case of an incident;
• Structural integrity and space management. By following setback rules, we ensure the construction is durable and your lot has proper ventilation, not deterioration of your quality life;
• Privacy concerns. By establishing setback rules that make owners maintain a healthy distance between the lots, governments help to promote privacy in the neighborhoods;
• Pathway for workers and services. Having space between the ADU and property lines allows easier access for construction workers as well as for utility maintenance stuff, delivery services, guests, and the owners themselves.

All in all, ADU setbacks are crucial for safeguarding your property and providing comfort to both property owners and their neighbors.

Setbacks for Different ADU Types

For a detached ADU, California zoning laws and local ordinances establish a reduced setback requirement of 4 ft. However, the size and height of your detached ADUs also play a role in determining the setbacks. This way, ADUs less than 1000 sq. ft. have reduced setbacks, while ADUs from 1000 to 1200 sq. ft. have not. Also, two-story ADUs (ADUs higher than 16 ft.) are subject to standard setbacks.

The attached ADUs have different rules. They may have setbacks applied to the primary residence since many attached ADUs are adjacent to the main house. So, it means more than 4 ft. Also, ADUs attached through a covered walkway may demand larger setbacks because of fire safety regulations and building code requirements. These ADUs are not as common, but due to architectural preferences or plot constraints, some homeowners opt for these types of construction.

The rules about how far a garage conversion needs to be from property lines are also peculiar. The original location of your garage (or carriage house) and its position in relation to other existing structures greatly influence the setbacks.

Corner Lots Setbacks

If your property is at the corner of two intersecting streets, you have a corner lot. In this case, you have two facades instead of one, like most lots do.

There are a couple of main rules determining setbacks for such unique properties:

1. On a corner lot, your front property line is at the narrower street frontage. The other front side is a street side (or side property line) with a setback of 4 ft;
2. If your lot has two fronts, each of the street-facing sides of your parcel are front property lines. However, if one of the sides has traffic banned by local authorities, it becomes a rear property line with a setback of 4 ft.

Summing up, corner lots have more complex rules than regular lots, so they require more attention to detail when building an ADU. If you’re the owner of a corner lot, it’s advisable to consult with professional ADU builders or other specialists adept at local ADU building requirements.

ADUs Fire Safety

The California Building Code establishes a set of fire safety rules related to various aspects of ADU buildings. In high-fire-risk zones or areas with densely built-up landscapes, fire safety standards are stricter than in other zones.

Thus, for an ADU to meet fire safety standards, it’s essential that there be enough space between the ADU and neighboring structures. These distances are usually ten ft. or more. Also, when you build one ADU unit atop or next to another, the materials and design used for these units should be capable of enduring fire for a specific time period to guarantee safety. Examples of necessary components might be enclosed overhangs, tempered glass, and flame-retardant stucco.

Adding a Fire Sprinkler

In the majority of cases, ADUs do not require fire sprinklers. Although, there are a few cases that stand outside of this rule. They include:

• In multi-family households and high fire hazard zones, if your main residence has fire sprinklers, an ADU should have them as well;
• If the ADU’s location is more than 140 ft. from the curb, you may need to install fire sprinklers, the number of which differs depending on the area. This is due to pulling the hose from the fire truck. Some fire stations might not have hoses that can stretch that far to put out a fire if it occurs in the ADU.

Fire sprinklers are not a very cheap addition to your ADU, even though they are a life-saving one. Depending on the ADU size, they can cost from $5,000 to $10,000, with some extra upgrading expenses possible.

Frequently Asked Questions — FAQ

What’s one drawback of an ADU?

A significant drawback of ADU building is the potential expenses and bustle associated with ensuring compliance. An ADU cost encompasses not only construction costs but also various permitting fees and site preparation expenses. Area-to-area differences as well as those necessary to meet complex requirements can cause prolongations and extra spendings.

What qualifies as an ADU in California?

An accessory dwelling unit (ADU) is a residential unit on the land with an already existing primary home. An ADU structure must meet zoning ordinances and other legal requirements to receive the status of a lawful ADU. These rules include setback requirements, height and size limitations, zoning rules, and many more.

Why is an ADU an affordable housing option?

Local governments put great effort into addressing housing shortages in areas with high population density. ADUs are an effective way to diversify residential spaces and make them more multi-purposed. Some cities and counties offer financial aid specifically for ADU construction, while some banks provide renovation loan options with lucrative rates for financing ADU construction.

What is the difference between an ADU and an addition?

While an addition is a part of your house, an ADU is typically a separate structure. Even speaking about attached units or internal ADUs, we still note that laws consider them self-sufficient residential units. A home addition is just an extension of an existing home, not a new, distinct home.