Differences Between Attached & Detached ADUs

The common difference between attached and detached ADUs is that an attached ADU shares a wall with the main residential unit despite having a separate living space. On the other hand, a detached ADU is separated from the main residential unit by a certain piece of open land.

If you want to build a detached ADU in Bay Area without any hassles, then you should contact ADU Specialist Bay Area. So, let us understand the difference between the attached and detached ADUs.

Attached ADU

The attached ADU is a separate section but is still connected to your main house. However, you have to build a separate entrance for this unit so that it can fulfil the legal requirements of an ADU. This unit helps to generate more space in your house.

Detached ADU

The detached ADU is a separate house built on your property. This house is eligible for one bedroom, one kitchen unit, and one bathroom and can be an ideal home for your parents where they can stay comfortably with all amenities available. Moreover, you can rent this place for some extra income.

Difference between detached and attached ADU

Maximum Size

There are restrictions for the maximum size of an attached or detached ADU.

The attached ADUs cannot be bigger than 50% of the main residential unit.

On the other hand, a detached ADU can be as big as 1200 square feet regardless of the size of the main residential unit. There are restrictions in some countries that restrict the size limit; however, a detached ADU can be built on a minimum area of 800 square feet no matter which area you belong to.

Construction Costs

Detached ADUs are more expensive than attached ADUs as attached ones are built from scratch. They share one or more walls with the primary residential unit. You will also require fewer raw materials to build this type of ADUs.

On the contrary, the detached ADUs require a separate foundation and thus construction costs exceed accordingly. You will require adequate raw materials to build such ADUs. So, their cost is almost equal to a small newly constructed building.

Potential Rental Earnings

You might earn a higher rental income from a detached ADU than an attached one. Here are the reasons:

Detached ADUs have more square footage as they are not restricted to being built on half of the area of a main residential unit. Hence, if you want to rent this unit, then you will get higher rental earnings because of the bigger area.

On the other hand, attached ADUs have restrictions as far as the size is concerned.

Secondly, a detached ADU is tenants’ first choice as it offers more privacy than the attached ones. Hence, you can make a fair amount of rental earnings from a detached ADU than an attached one.

Parking Requirements

The parking requirements vary for different types of ADUs. So, the same rule does not apply to all types of ADUs built on your property.

You can have at least one off-street parking space for a detached ADU. The parking can either be covered or uncovered. You can build a parking lot at the front, rear, or side of the ADU unit.

On the other hand, for attached ADUs, the parking requirements depend on the location of the ADU. Sometimes, the ADU is located in the basement or attic of the main residence or sometimes it is located on the exterior part of the house. So, for an exterior attached ADU, you can have one off-street parking space of its own, just in case of detached ADUs.

But, for an interior ADU, you do not have to build a separate parking space.

Property Valuation

An ADU adds value to your property. However, there are differences in resale value based on the type of ADU built on your property.

A detached ADU can increase the value of your property compared to an attached ADU. However, an attached ADU helps you make the best use of the space by increasing the square footage of your primary residential unit.


If you want to build an ADU to add value to your home, then you should hire a trusted ADU contractor in your location to avoid future hassles.