You can classify accessory dwelling units (ADUs) into one of two main categories: detached ADUs (DADUs) and attached ADUs. A DADU is a standalone structure that shares land with the main house. This type of unit is also known as a granny flat, backyard cottage, or mother-in-law apartment. An attached ADU, as its name suggests, is built in a way that’s connected to the main house.
If you’re thinking about adding an ADU to your home, you might want to know how the attached and detached units differ. Below, learn all about the attached ADU vs. DADU divide so you can determine which unit might be best for your property.
12 key differences and similarities between an attached and detached ADU
While both attached ADUs and DADUs are full-on homes, several factors differentiate the two. At the same time, there are also many ways in which the two are similar. Below are 12 factors that can help you compare these units and decide which might be better for you.
Attached ADU vs. DADU differences
Below are some of the key points that differentiate AADUs from DADUs.
Placement. The primary difference between an AADU and a DADU is its placement. An attached ADU is connected to the main house. It shares a wall with a room in the house. A detached ADU, on the other hand, is separate from the main house and acts as a smaller home.
Privacy. A DADU is removed from the main house, so it gives residents more privacy than an attached ADU. A fence, yard, or outdoor divider might further separate the two living spaces. Residents can come and go as they please with little to no interaction with the people living in the main house. They won’t overhear conversations among other people in the household or worry about prying housemates. While residents of an attached ADU have their own living space and entrance, they may not have as much privacy because of a shared wall.
Size. Attached ADUs and DADUs may differ quite significantly in terms of square footage. Attached ADUs are often smaller than detached ADUs since they’re often limited by the physical restrictions of your home. Notably, in some locales, you also cannot add on more than half of the square footage of your existing structure.
Cost. Attached ADUs can be less expensive than custom, stick-built DADUs but more expensive than prefab, off-site construction DADUs. A turnkey ADU service provider can help you determine whether an attached ADU or an off-site construction DADU will be more affordable. For example, with Spacial, 400-square-foot studio DADUs start at $139,000, and 500-square-foot one-bedroom ADUs start at $157,000. These prices often undercut attached ADU prices when adding Spacial’s end-to-end turnkey ADU services. Plus, in the long run, Spacial’s solar photovoltaic (PV) rooftop system and high-efficiency HVAC will keep your utility bills low too.
Design. With an attached ADU, your options for design and customization may be a bit limited since you have to consider the existing house. With a detached ADU, you have design options ranging from front and top paneling colors to the landscaping surrounding the unit.
Passive income. About 51 percent of new ADUs in California serve as rental units. Renting out a detached ADU will often bring in more income than with an attached ADU. DADUs are often larger, and they always have more privacy, so tenants are often willing to pay more to rent them.
Photo by Spacial
Attached ADU vs. DADU similarities
AADUs and DADUs are similar in ways mostly related to the benefits they can bring to your property. Below are some key similarities between attached and detached ADUs.
Purpose. Both attached ADUs and detached ADUs can create useful additional living space on your existing property. You can use these units to house older adults in your family, out-of-town guests, and renters, or you and your family can utilize the space as a work area, studio, or private getaway.
Property value increase. Adding an ADU to your lot can immensely increase your property’s value. On average, an ADU in California is valued at about $235,545. But in places where the cost of living is higher, like the bay area, the ADU is valued much higher. Your ADU’s type, size, and will influence its value, but even a relatively basic garage conversion can bring some significant value to your property. That’s on top of creating the opportunity for rental income.
More square footage. Even the smallest ADU (the typical minimum is 300 square feet) adds more liveable space in your home or on your property. The amount of space an ADU adds can be significant: The average size of new ADUs in California is 615 square feet. Even if you opt for an attached ADU, you’re maximizing the amount of square footage you can use as livable space.
Applicable for local funding and grants. If your income falls at or below a certain limit, you could qualify for a grant to help you finance your attached or detached ADU. The California Housing Finance Agency (CalHFA) runs a grant program that could reimburse you up to $40,000. This program is designed to help you cover pre-development costs (site preparation, permits, property surveys) involved in building an ADU.
Similar permit processes. Whether you’re adding an attached ADU or building a detached ADU, you’ll need to ensure your unit adheres to local guidelines. Fortunately, the permit processes for AADUs and DADUs are similar. You’ll first need to check if your property is eligible for a new ADU. From there, you’ll need to fill out a permit application. Your application will first undergo an environmental review. City planning staff will then review your ADU’s design and lot size to assess the construction and new features you want to add. The planning department will then send everything to the building department for final review. You’ll then receive your permits once your application is approved.
Customizable amenities. Both AADUs and DADUs need appliances, furniture, and fixtures. You can customize each of these features so they fit the vision you’re aiming to achieve. Or you can rely on a turkey ADU services provider like Spacial to handle all these parts for you. Yes, custom appliances and fixtures are nice, but they can inflate your budget, and you have to arrange for their installation. Spacial ADUs arrive with all appliances and fixtures ready to go, and we’ll also furnish your ADU through our West Elm partnership. You’ll feel right at home, right away.
An ADU can bring some great benefits to your property, especially a detached ADU. This type of ADU can add significant value, additional square footage, and the potential for higher rental income. If you think a DADU is the ideal unit for your property, Spacial can help you take your idea and turn it into a reality.
At Spacial, we offer two options for detached ADUs: a studio and a one-bedroom unit. Our studio provides plenty of room to give family, friends, or tenants an open and inviting living space. If you’re looking for a slightly larger setup, our one-bedroom ADU offers a spacious, warm, and modern layout.
When you choose to work with Spacial, you leave all the hard work to us. We’ll take care of the surveys and permits to expedite the approval process. From there, our team will construct your ADU off-site. While we do that, we’ll lay the foundation for your unit and install the systems needed to make your ADU functional. Once your unit is complete, we’ll hook it up to our crane and safely install it right on your property in just one day.
The process of planning and building a detached ADU can be a lot easier than you might think. Contact Spacial today to start planning your vision.
