Tiny Houses and ADUs – What’re the Differences?

Lately, I’ve been getting emails asking if a Tiny House could be used as an Auxiliary Dwelling Unit (ADU). This seems like something everyone should know by now but there are some big differences.

Tiny House

Tiny House

A tiny house and an auxiliary dwelling unit (ADU) are both types of compact, self-contained dwellings, but they differ in their intended use and legal definitions.

Size and Mobility:

Tiny House: A tiny house is typically a small, freestanding dwelling that ranges in size from around 100 to 400 square feet. It is often built on a trailer bed and designed to be movable, allowing for flexibility in location.

Auxiliary Dwelling Unit (ADU): An ADU, also known as a backyard cottage, granny flat, or in-law suite, is a secondary housing unit that is located on the same property as a primary residence. ADUs can be either attached or detached from the main dwelling and are generally larger than tiny houses, ranging from a few hundred to over 1,000 square feet.

Auxiliary Dwelling Unit

Legal Status and Regulations:

Tiny House: The regulations surrounding tiny houses can vary significantly depending on the jurisdiction. In some places, they may be classified as recreational vehicles or park models, subject to specific zoning or building codes. In other areas, they may need to adhere to traditional housing standards, which can limit their mobility and placement options.

Auxiliary Dwelling Unit (ADU): ADUs are typically subject to local zoning and building regulations. Many cities and municipalities have specific guidelines regarding their size, design, parking requirements, and permitted locations. ADUs are often intended for long-term residential use and must comply with local housing codes.

Purpose and Function:

Tiny House: Tiny houses are often associated with minimalist living, sustainability, and mobility. They are sometimes used as primary residences, but they can also serve as vacation homes, guest houses, or even office spaces.

Auxiliary Dwelling Unit (ADU): ADUs are primarily intended to provide additional housing options on existing residential properties. They are commonly used to accommodate family members, such as aging parents or adult children, or to generate rental income. ADUs are usually designed with more amenities and functionality, including separate living spaces, kitchens, and bathrooms.

Here’s a chart showing the differences:

While there may be some overlap in design and features between tiny houses and ADUs, the key distinctions lie in their size, mobility, legal status, and intended purpose. It’s important to consult local regulations and zoning laws to determine the specific requirements and definitions in a particular area.

Gary Fleisher

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Gary Fleisher

Gary Fleisher, “The Mod Coach”, has been entrenched in the offsite construction industry for most of his life. Having started his career in the lumber industry, Gary spent decades working with manufactured and modular home producers and homebuilders. For the past 15 years his blog and LinkedIn postings have introduced thousands to the benefits of factory-built construction and have served as a forum for industry professionals to share insights and perspectives. Gary lives in Hagerstown, MD with his wife, Peg.

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