Accessory Dwelling Units (ADU’s)

The City of Arvada's unique and vibrant character attracts new visitors and not-yet-residents from near and far. My wife and I experienced its unmistakable charm firsthand when we visited Olde Town Arvada during the search for our first home. We instantly knew that Arvada was where we wanted to settle down. However, despite both of us working full-time, finding an affordable property proved to be a challenge. In 2014, we finally purchased our first home, but felt we had overpaid and were concerned about our financial stability. Unfortunately the affordability crisis has only accelerated over the past 10 years.

The Challenges

One of the key challenges with housing affordability in our city stems from the types of new construction being developed. Most new buildings are either high-density rental apartments or low-density larger homes, resulting in a shortage of smaller, more affordable options like starter single-family homes, duplexes, condos, and townhomes. Various factors contribute to this issue, including local code requirements, land costs, the permitting process, and state-level concerns like construction defects litigation (which make 'missing middle' housing a risky endeavor for builders and investors).

The Opportunities

As a local government, our City Council has multiple avenues to enhance the diversity of housing options, including the 'missing middle,' that are brought to market each year. While I'll dive into more of these strategies in future blogs, I want to concentrate on what City Council can do to make it easier to turn your backyard into an extra space for an aging parent, a revenue generator, help tackle the housing crisis, or become more familiar with local building rules and regulations. Let's make it easier to build ADUs (Accessory Dwelling Units) in Arvada!

What is an ADU? 

An accessory dwelling unit (ADU), also known as a “mother-in-law” or “granny flat,” is an attached or detached residential dwelling unit that provides complete independent living facilities for one or more persons on the same parcel as the main dwelling unit. This includes permanent provisions for living, sleeping, eating, cooking, and sanitation. There are several different types of ADUs and Arvada’s wide variety of lot sizes and configurations means that documenting every possible layout is nearly impossible.

Are there currently ADUs in Arvada? 

ADUs have been allowed in Arvada for over a decade and have experienced a relatively consistent 10 new units per year. They are popular options for all corners of our City. Arvadan’s build a decent number of ADUs, but not as many as other cities with supportive rules and policies for ADUs. If those cities are a guide, Arvadan’s could be building up to 10x more ADUs with more supportive policies than they are now. Recently, the state has mandated the removal of some restrictions that make ADUs more appealing for some homeowners. However, the largest hurdle for most interested in exploring ADUs as an option for their property is cost.

New State Laws affecting ADU’s:

Colorado's 2024 ADU laws, enacted by House Bill 24-1152 took effect on June 30, 2025, and mandated that all municipalities must allow at least one ADU in areas zoned for single-family homes. Key changes include setting maximum setbacks, requiring a minimum lot size equal to the primary home's, and allowing ADUs of 500-750 square feet. The law prohibits restricting ADUs with design standards more stringent than the primary dwelling and restricts requiring owner occupancy or parking for the ADU, except in limited circumstances. 

Key Mandates of the New State ADU Laws

• By-Right ADUs: Municipalities must allow at least one ADU as a permitted use in all areas where single-unit detached dwellings are allowed. 

• Administrative Approval: An administrative process, rather than a discretionary one, must be used to approve ADU permits. 

• Size Requirements: ADUs are generally required to be between 500 and 750 square feet, but specific local rules may allow for larger sizes. 

• Setback Requirements: Setbacks for ADUs cannot be more restrictive than those for the primary dwelling, with a mandatory 5-foot rear yard setback allowed in the absence of existing limitations. 

• Lot Size: The minimum lot size requirements cannot exceed those for the primary single-unit detached dwelling. 

Prohibitions for Municipalities

• Design Standards: Local governments cannot apply architectural style, building materials, or landscaping requirements to ADUs that are more restrictive than those for the primary dwelling. 

• Owner Occupancy: Municipalities are generally prohibited from requiring the owner to live in the primary home or the ADU. 

• Parking: New off-street parking cannot be required for an ADU, with exceptions for parcels lacking any existing off-street parking and where on-street parking is prohibited. 

Mike’s Proposed Solution: Preapproved ADU plans 

The cost to develop architectural plans, engineering drawings, and the time and money required to move through the permitting process at the City could be streamlined substantially making ADUs a more affordable option for homeowners. Other communities have done this and seen a ten-fold increase in the number of ADUs successfully implemented in one year. 

Example of preapproved plan set:

By providing pre-approved ADU plans, residents can save time and money. Interested homeowners, with sufficient space, can download plans from the city website, choose one that fits their lot configuration, and contact the listed prefabrication vendor to get started. ADUs have become popular for prefabrication methods, where the new structure is delivered largely complete or with minimal additional construction needed. Prefabrication is another opportunity for homeowners to save money on labor and assembly costs. 

Example of a prefabrication floor plan:

While some property owners may opt for a custom build, which could be as expensive as purchasing a small new home, others find the current process and costs prohibitive. This solution, successful in other cities, benefits the city, property owners, and people seeking more housing options. This one housing product increase will not solve our affordability crisis, but it will increase our housing stability and resilience as a city.

Here is a fun website that allows you to customize your prefabricated ADU down to the flooring and it comes fully assembled ready to crane-in to your location for about $120,000!

As your next City Council representative in the At-Large seat, I am committed to working with community members, staff, homebuilders, and my fellow council members to find practical solutions and forge partnerships that provide housing options and opportunities for all Arvadans.