Which ADU Is Right For You?
November 3rd, 2024
Chris Koss, AIA
While different types of ADUs serve various functions, the right type of ADU for you may vary depending on your design preference, the size & shape of you property, and your location's zoning regulations. Already know what type of ADU you want? Click here to see the AIA|LA's top designs of 2024 for design inspiration. Don't know what type of ADU is best for you? Here's a list of each type of ADU and which type we suggest you should build based on how you want to use it:
As the most versatile and popular ADU type, a detached ADU is a detached dwelling constructed independently from the front house. It often resembles a cottage or a guest house and is built to the side or behind the front house. While the detached ADU type offers the widest range of use applications, with a construction cost of $350-$500 per square foot, detached ADUs are also the most expensive type to construct. Although detached ADUs are a great solution for housing elderly parents or adult children, housing a workspace or studio space, and even caregiver housing, detached ADUs are the most popular type of ADU for rentals as they're effectively single-family homes - the most attractive housing type for most tenants. Your yard is a highly attractive amenity especially for tenants with pets or children who will absolutely love having a yard for running around or playing. As a standalone building, tenants are typically more willing to pay a premium for physical autonomy from the front house especially if there is still enough space for a yard.
We recommend a detached ADU for homeowners looking for steady short and/or long term rental income.
Attached ADUs share at least one wall with the primary home but, in most cases, maintains status as an additional unit by having its own separate entrance. Besides being the best option for smaller lots, attached ADUs are typically easier to permit and require less material. By attaching to the primary/front house, the attached ADU option is the best option for a smaller lot size since you wouldn't need to provide required setbacks as you would for a detached ADU. Considering that attached units cost about $300-$400 per square foot, an attached ADU could be the best option for a tight property and limited budget. The attached ADU type gives more independence to elderly parents or adult children without leaving the property. If you intend to house aging or handicapped family members on your property but they still would prefer some separation, then the attached ADU style may be your best option. For those retirees who need healthcare most days or everyday but don't want to give up their home and move into a nursing home, attached ADUs offer a desirable amenity for dedicated caregivers to live closer to their patients' homes. AARP has become a strong advocate for adding ADUs to accommodate multigenerational families and caregivers for older adults.
We recommend the attached ADU type for homeowners who wish to provide independent housing for caregivers and multigenerational housing.
Another popular choice for homeowners, a garage conversion ADU is an existing garage that's been renovated into a habitable unit, often with a kitchen, bathroom facilities, fitness room, artist studio, and/or a home office. If you intend to build an ADU for your business or hobby, the garage conversion type may be the right application for hosting a private workspace or studio separate from the front house. As the garage conversion typically displaces car storage, it's typically less desirable as a rental unit. As this type converts an existing structure into a new use, the garage conversion construction budget is one of the most cost-effective, costing around $100,000 to $130,000. For our wedding's first dance, my wife and I took lessons in our dance instructor's ADU, and it was the perfect space to learn all the moves while our instructor saves thousands of dollars a month on studio rental fees!
For these reasons, we recommend the garage conversion ADU type for a home office or studio space.
For homeowners who own a large enough property and wish to maximize their backyard's earning potential, the duplex ADU type is a great choice for building multiple rental units. With comparable construction costs to the detached ADU, a duplex ADU is a popular choice for homeowners to generate two rental incomes in their backyard.
While all ADUs need to address parking requirements, if you're considering building a duplex ADU, you especially need to consider parking requirements: California state legislature limits the required parking for an ADU to one parking space per unit or per bedroom and permits the parking space to be a tandem space in an existing driveway. State legislation further stipulates that parking cannot be required when an ADU is located within ½ mile of public transportation or within an historic district, which would permit a duplex ADU to be built even on a smaller lot.
We recommend the duplex ADU type for homeowners who want to generate two rental incomes in their backyard, especially when their property is within ½ mile of public transportation or within an historic district.
For homeowners who would like to provide housing for a family member or caregiver within their basement, finished or unfinished, a basement conversion ADU is an excellent, cost-effective choice that provides independent access to a housing unit within the home. As the most cost-effective ADU type, the basement conversion typically costs around $30,000 to $75,000.
Given the conversion nature of basement conversion ADUs, California law states that parking is not required for ADUs located within a primary residence or when a car-share vehicle is located within one block.
We recommend a the basement conversion ADU type for homeowners who want to provide housing for a caregiver or family member.
Junior ADUs (JADUs) are the most versatile and simple ADU type, are no more than 500 square feet, and have two different applications: internal and detached. An internal JADU is typically a bedroom in a single-family home that has an entrance into the unit from the main home and an entrance to the outside from the JADU. A detached JADU is simply a separate structure from the primary house. Each JADU must have cooking facilities, including a sink, but is not required to add a private bathroom and may share a bathroom with the primary home. While not required, many local ordinances, including Los Angeles, have permitted JADUs.
As the simplest and most affordable housing option, internal JADUs bridge the gap between a roommate and a tenant by offering an interior connection between the unit and main living area. The doors between the two spaces can be secured from both sides, allowing them to be easily privatized or incorporated back into the main living area. These units share central systems, require no fire separation, and have a basic kitchen, utilizing small plugin appliances, reducing development costs. This provides flexibility and an insurance policy in homes in case additional income or housing is needed. They present no additional stress on utility services or infrastructure because they simply repurpose spare bedrooms that do not expand the homes planned occupancy. No additional address is required on the property because an interior connection remains.
As an added benefit, a JADU does not require additional parking.
For homeowners who simply want to rent out a bedroom in their house as a unit or add a home office or studio space as an independent structure to their backyard, the detached JADU is the most cost-effective and time efficient option.
