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Understanding Adu Laws: Which States Permit Accessory Dwelling Units?

Understanding Adu Laws: Which States Permit Accessory Dwelling Units?

Picture of the owner of Birkes BuildersDavid Birkes
Owner | General Contractor & Builder
Birkes Builders
Published On:
August 15, 2023
Last updated:
August 15, 2023
a couple of small wooden buildings sitting next to each other

What states allow adu

Introduction: What is an ADU and Why is it Important?

Demystifying the ADU Concept

An Accessory Dwelling Unit, or more commonly known as an ADU, might seem like a complex term to decipher at first glance. But fear not, for it's nothing more than a secondary living space constructed on a property that already houses a single-family dwelling.

This could be a detached structure in your backyard, a basement apartment, or even an over-the-garage loft. These units come complete with kitchen facilities and bathrooms, thus creating an autonomous living space within the same residential lot.

The Appeal of ADUs

What makes them so appealing? Well, the reasons are manifold. For starters, they increase property value significantly by adding usable living space without necessitating new land.

Plus they offer flexible housing options - perfect for aging parents who want to maintain independence while staying close to family; young adults seeking some privacy without breaking the bank; or even homeowners yearning for that passive rental income. Hence, these versatile domiciles are gaining tremendous popularity across US states.

The Significance of Understanding Statewide Regulations

However intriguing they sound though, building an ADU isn't just about picking up your toolkit and getting started right away! There are zoning laws and building regulations you need to navigate before embarking on this exciting endeavor.

And those regulations can vary significantly from state to state - which brings us back full circle as to why we're discussing this topic today! By understanding the legal landscape around accessory dwelling units in different states across America, you'll be equipped with crucial knowledge before taking that big leap towards adding an ADU to your property.

The Big Picture: States Embracing the ADU Concept

Across America, a quiet revolution is reshaping the landscape of our residential neighborhoods with the advent of Accessory Dwelling Units (ADUs). These humble abodes, colloquially known as "granny flats," "in-law suites," or "backyard cottages," offer a potent solution to the increasing housing crisis.

They maximize land use, provide affordable housing options and foster multi-generational living. In these changing times, many states are showing an unprecedented receptiveness towards this niche concept.

Let's embark on a journey across America, exploring states that are embracing ADUs and their unique approaches. We will navigate through the West Coast pioneers who sowed the seeds for this movement; trek to East Coast enthusiasts adopting this trend; lastly, we'll pay homage to heartland adopters who didn't let geographic location deter their progressive stance on ADUs.

Westward Ho! The West Coast Pioneers: California, Oregon, and Washington

The Golden Embrace of California

Leading the charge is California with its progressive stance on ADUs. The Golden State recognized early that ADUs could be instrumental in addressing its burgeoning housing crisis.

It passed numerous laws easing restrictions and fast-tracking approval processes for ADU construction. Beyond reducing bureaucratic red tape, California also encourages local jurisdictions to adopt more flexible guidelines of their own.

This has led to some truly innovative local policies further incentivizing homeowners to consider building an ADU on their property. California's story is not just about policy changes; it's about communities witnessing firsthand how these compact dwellings can transform lives by providing affordable living options while enhancing neighborhood dynamics.

Oregon's Ode to Diversity in Housing

Moving northward brings us Oregon -- a state famous for its commitment to sustainability and diversity in housing. Portland has been particularly proactive - instituting pilot programs encouraging homeownership with rental opportunities via constructing backyard homes. Oregon's approach stands testament that thoughtful policies which value human scale can lead towards more diverse neighborhoods.

Bend's building codes serve as a prime example where accessory dwelling units play a pivotal role in maintaining the city's unique charm while addressing modern housing needs. This Pacific Northwest tales showcases that encouraging construction of unassuming small dwellings can make large strides towards more inclusive communities -- striking harmony between preservation and evolution.

The Evergreen Crusade: Washington State

Few states have welcomed backyard cottages quite like Washington State. Seattle led the way by significantly relaxing regulations around constructing accessory dwelling units and even advocating for multiple such units per lot! This radical approach emerged from Seattle's intent to increase density without altering neighborhood character significantly - an innovative model garnering attention nationwide.

Spokane follows suit with little-known laws allowing conversion of existing structures into income-generating homes thereby fostering economic resilience at grassroots level. In essence, Washington State's narrative reveals how cities can convert constraints into opportunities - leveraging limited land resources into creating homes-for-all without sacrificing community spirit or aesthetics.

State-by-State Breakdown of ADU Regulations

California's Progressive Stance on ADUs

California, the sunshine state, seemingly always at the vanguard of progressive practices, has adopted an incredibly forward-thinking stance when it comes to Accessory Dwelling Units (ADUs). The state serves as a beacon of hope for those hoping to add such units to their properties.

Local Jurisdiction Flexibility

The pioneering spirit doesn't stop at the state level -- local jurisdictions are given leeway to mold policies suiting their unique conditions and housing needs. For example, San Francisco allows homeowners in certain neighborhoods to convert existing structures into ADUs without worrying about parking requirements or unit caps. Contrastingly, in Los Angeles County, while still supportive of ADUs, regulations are slightly more stringent with caps on sizes and designs depending upon zoning.

Tiny Details of California's Statewide Standards

The statewide standards serve as a flexible framework for ADU development. No minimum lot size is required for adding an ADU; however, setbacks from property lines must be maintained.

Furthermore, owner-occupancy requirements have been eliminated until 2025 for most single-family and multifamily lots. The fine-grained details that California's laws provide makes them a lodestar among states that allow accessory dwelling units.

Oregon's Green Light for Granny Flats

Let's turn our gaze northwards where Oregon has shown its own commitment toward more inclusive zoning laws and embracing the green light given to granny flats or as they call them there - 'Accessory Dwelling Units'.

Portland's Pilot Program Details

The city of Portland has become a hotbed for ADU construction after initiating an encouraging pilot program aimed at increasing affordable rental housing options. The city offers financial incentives including waiving System Development Charges (SDCs) saving homeowners tens of thousands on their construction costs.

Quirky Facts about Bend's Building Codes

In contrast to Portland's bustling urban environment is Bend - where the focus on building codes revolves around maintaining its small-town charm amidst rapid growth. It limits detached ADUs to single-story structures and requires design elements that blend with the primary home. Despite these restrictions though, Bend has seen robust growth in new constructions signifying its residents' adaptive nature!

Washington's Welcoming Policies for Backyard Cottages

Drawing inspiration from its southern neighbors we now journey towards Washington State known not just for its space needles but also its welcoming policies towards backyard cottages or "Detached Accessory Dwelling Units".

Seattle's Sweeping Changes

In Seattle - the jewel in Washington State's crown - recently enacted changes have made way for increased density via DADUs. Removing parking requirements along with relaxing lot size and owner-occupancy rules have allowed homeowners greater flexibility in adding such units.

Little-known Laws in Spokane

Moving eastwards within Washington reveals Spokane which enforces distinctive rules surrounding DADUs like limiting these structures' height based on proximity to neighboring homes ensuring privacy is upheld while still promoting infill development. The city also demonstrates how suburban areas can successfully incorporate accessory dwellings into their communities.

Emerging Trends in Other States

The Resolve of Massachusetts: Transforming Housing Through ADUs

In the world of accessory dwelling units, Massachusetts is demonstrating that taking measured strides can lead to significant change. The state has recently exhibited a growing fondness for ADUs, and no city embodies this shift more evidently than Boston.

Boston, a city famous for its historic neighborhoods and brownstone buildings, is not one to shirk from bold steps when it comes to housing innovation. The city has embraced the concept of ADUs with an enthusiasm that is gradually transforming its landscape.

With municipal laws encouraging homeowners to build these units either within or as extensions to their existing homes, Boston's housing situation is undergoing an optimistic metamorphosis. The revolution isn't confined solely to Boston though; it has spread its wings across the state.

Nestled amongst this trend is Worcester--whose lesser-known legislative changes could potentially have considerable impact on their housing crisis. Worcester's zoning code revisions have made room for ADUs in single-family dwelling districts--an admirable attempt at addressing affordability issues through increased density.

Vermont's Progressive Stance: Aiming for Versatility in Housing

Vermont, known for its picturesque landscapes and tranquil lifestyle, seems an unlikely pioneer in the realm of versatile housing solutions such as ADUs. But step into Burlington and you'll find a city using forward-thinking initiatives to accommodate its growing population.

Burlington sees beauty in diversity--not just in its people but also in its housing options! The city's blueprint for success lies in promoting ADU development as part of their comprehensive plan by allowing homeowners to create additional living spaces either within or added onto their existing homes--a solution both practical and sustainable.

Yet there's more still hidden beneath Vermont's charming facade; secrets nestled deep within Montpelier's Municipal Code reveal unexpected support for the construction of accessory dwelling units. These hidden gems include provisions that allow homeowners flexibility regarding where they can locate an ADU on their property--be it attached or detached--all while providing affordable rental options amidst rising living costs.

Case Studies of Unexpected States with Friendly ADU Policies

Colorado's Surprising Support for Secondary Suites

Daring Development Decisions in Denver

You might not expect it, but Denver has shown itself to be quite the maverick when it comes to the development of accessory dwelling units (ADUs). In recent years, this rustic Rocky Mountain metropolis has made daring decisions that pave the way for more secondary suites in residential zones. Progressive policy changes have encouraged homeowners to explore adding ADUs onto their properties, creating a boon in diversified housing stock.

The Obscure Ordinances of Boulder

Let's head northwest up Highway 36 to Boulder, another Colorado city that embraces the concept of ADUs. Known primarily for its vibrant college community and stunning Flatirons backdrop, Boulder also boasts some obscure ordinances supporting secondary suite development. The city updated its regulations in 2018; among other things, these guidelines now permit an increased number of occupants based on lot size and reduce parking requirements.

Minnesota's Model Approach to Accessory Apartments

Minneapolis' Major Moves

Moving northward now to Minnesota and specifically Minneapolis - this city is making major moves towards allowing more homeowners to reap the benefits of having an accessory apartment. With relaxed zoning laws that include all residential property types across every neighborhood, Minneapolis is setting a new precedent by embracing a universally inclusive approach.

Rarely Recognized Rules in Rochester

It would be remiss not to mention Rochester when highlighting Minnesota's pioneering approach toward ADUs. Despite being far less recognized than its metropolitan cousin Minneapolis, Rochester holds its own with forward-thinking rules and regulations encouraging ADU construction. As one example: they've eliminated lot-size requirements entirely!


As we've journeyed from coast-to-coast exploring Accessory Dwelling Unit (ADU) legislation state-by-state, it's clear there are innovative housing solutions emerging nationwide. From major metropolitan areas like Denver and Minneapolis taking bold regulatory steps, smaller cities like Rochester are also making their mark with groundbreaking approaches as well. As we look toward a future where housing needs continue evolving rapidly - affordability challenges persist - let's remain optimistic about creative solutions like ADUs playing a critical role in addressing these issues.

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