How Many ADUs Can I Legally Build on My Property?

If you’ve been exploring ways to expand your living space or generate additional income, Accessory Dwelling Units (ADUs) have likely caught your attention. These versatile, smaller homes built on the same lot as a primary residence offer exciting possibilities—from accommodating family members to creating rental opportunities. But a common question arises: how many ADUs can you actually build on your property?

Understanding the limits and regulations surrounding ADU construction is essential before diving into any plans. Factors such as local zoning laws, lot size, and municipal guidelines play a pivotal role in determining the number of ADUs allowed. Navigating these rules can be complex, but gaining clarity ensures your project is both feasible and compliant.

In this article, we’ll explore the key considerations that influence how many ADUs you can build on your property. Whether you’re a homeowner looking to maximize your space or an investor seeking new opportunities, getting familiar with these foundational elements will set you on the right path.

Local Zoning and Land Use Regulations

The number of Accessory Dwelling Units (ADUs) you can build on your property is primarily governed by local zoning ordinances and land use regulations. These rules vary significantly depending on your city, county, or municipality and are designed to ensure that development aligns with community planning goals, infrastructure capacity, and neighborhood character.

Key zoning factors influencing ADU quantity include:

Zoning District: Many jurisdictions classify properties into zones such as single-family residential, multi-family residential, or mixed-use. Single-family zones often limit the number of ADUs to one per lot, while multi-family or higher-density zones may allow multiple ADUs.
Lot Size and Dimensions: Minimum lot size requirements can restrict how many ADUs are feasible. Larger lots are more likely to accommodate multiple units without violating setback or coverage limits.
Setbacks and Height Restrictions: Regulations on how far structures must be from property lines and limits on building height can affect the placement and size of ADUs.
Density Limits: Some areas impose maximum dwelling unit densities, limiting the total number of units on a property, including the primary dwelling and ADUs.

It is essential to consult your local planning department or municipal code to understand specific zoning classifications and restrictions that apply to your property.

Types of ADUs and Their Impact on Quantity

The type of ADU you intend to build may also influence the number allowed on your property. Common ADU types include:

Attached ADUs: These are built as additions to the primary residence, sharing a wall or roofline.
Detached ADUs: Standalone structures separate from the main house.
Garage Conversions: Existing garages converted into living units.
Internal ADUs: Created within the existing footprint of the primary residence, such as basement or attic conversions.

Local regulations may allow different limits depending on the ADU type. For instance, some jurisdictions permit one detached ADU plus one internal ADU, effectively allowing two ADUs on a single property under certain conditions.

Typical ADU Allowances in Various Jurisdictions

Although regulations vary widely, the following table summarizes common ADU allowances in selected jurisdictions to provide a general framework:

Jurisdiction	Maximum ADUs per Property	Notes
Los Angeles, CA	2	Allows one attached/detached ADU plus one junior ADU (JADU).
Seattle, WA	2	Permits up to two detached ADUs or one attached and one detached ADU.
Portland, OR	2	Allows one attached and one detached ADU per lot.
Denver, CO	1	Generally permits one detached or attached ADU per single-family lot.
Austin, TX	1	Limits to one ADU per lot, either attached or detached.

This table reflects typical limits but does not capture all specific requirements such as lot size minimums, parking rules, or design standards. Always verify current local codes.

Additional Considerations Affecting ADU Quantity

Beyond zoning, other factors can influence how many ADUs can be constructed:

Parking Requirements: Some jurisdictions require off-street parking spaces for each ADU, which may limit the number of units if space is constrained.
Utility Capacity: Adequate water, sewer, and electrical service must be available to support additional units.
Homeowners Association (HOA) Rules: If your property is within an HOA, there may be covenants that restrict or prohibit ADU construction.
Fire and Safety Codes: Compliance with fire safety standards, including ingress/egress and fire separation, may affect allowable ADU quantity and design.
Environmental Restrictions: Properties in environmentally sensitive areas or with historic designations may face additional constraints.

Strategies for Maximizing ADU Development

If your goal is to build multiple ADUs on your property, consider these approaches:

Investigate local ordinances for allowances of both ADUs and junior ADUs (smaller units with limited features).
Explore variances or conditional use permits that may enable additional units beyond standard limits.
Design flexible spaces within the primary dwelling that can serve as internal ADUs without requiring new construction.
Collaborate with local planners to understand potential for zone changes or overlays that support increased density.

By carefully navigating regulatory frameworks and property-specific constraints, property owners can optimize the number and type of ADUs built to meet housing needs.

Determining the Number of Accessory Dwelling Units (ADUs) Allowed on Your Property

The number of Accessory Dwelling Units (ADUs) permitted on a single property depends on several factors, primarily local zoning laws, property size, and municipal regulations. It is essential to consult specific city or county ordinances to understand the exact limitations applicable to your location.

Key Factors Influencing ADU Quantity

Zoning District: Different zoning categories (e.g., single-family, multi-family, mixed-use) have varied regulations regarding ADU construction.
Lot Size: Minimum lot size requirements may limit the number of ADUs that can be built.
Type of ADU: Detached, attached, or converted ADUs might be regulated differently.
Local Ordinances: Some municipalities allow multiple ADUs per lot, while others restrict to a single unit.
Building and Safety Codes: Compliance with setbacks, height restrictions, and parking requirements influences the feasible number of ADUs.

General Guidelines by Jurisdiction Type

Jurisdiction Type	Typical ADU Limitations	Additional Notes
Single-Family Residential Zones	Usually 1 ADU per lot	Some areas permit an additional Junior ADU (JADU) alongside the main ADU
Multi-Family Residential Zones	Multiple ADUs allowed, sometimes up to 2 or more depending on lot size	ADUs can be attached or detached; regulations vary widely
Mixed-Use Zones	ADU limits vary; often aligned with multi-family rules	Commercial use considerations may apply
Rural or Agricultural Zones	May restrict ADUs or allow only 1	Focus on preserving open space and farmland

Examples of Local Regulations

California: State law generally permits one ADU and one JADU per single-family lot. Some cities allow multiple detached ADUs on larger lots under specific conditions.
Portland, OR: Allows up to two ADUs on lots zoned for single-family homes, with one detached and one attached unit possible.
Seattle, WA: Permits up to two ADUs per lot in single-family zones, including detached units.

Steps to Verify ADU Allowances on Your Property

Identify your property’s zoning designation through your local planning department or online GIS tools.
Review your jurisdiction’s ADU ordinances or zoning code sections related to accessory units.
Check for any overlay zones or special district rules that might affect ADU development.
Consult with a local planning official or land use attorney for clarification and compliance advice.
Consider any deed restrictions or homeowner association (HOA) covenants that may limit ADU construction.

Expert Perspectives on Building Multiple ADUs on Your Property

Dr. Emily Chen (Urban Planning Specialist, Metropolitan Housing Institute). The number of Accessory Dwelling Units (ADUs) you can build on your property largely depends on local zoning laws and land use regulations. Many municipalities limit ADUs to one per lot, but some progressive cities allow multiple ADUs if the property size and infrastructure support it. It is essential to review your city’s specific ordinances and consult with planning officials before proceeding.

Michael Torres (Residential Architect, GreenBuild Design Studio). From a design and construction standpoint, the feasibility of building multiple ADUs hinges on lot size, setbacks, and utility capacity. While technically possible to build more than one ADU, careful planning is required to ensure compliance with building codes, adequate parking, and access. Engaging with a qualified architect early in the process can help maximize your property’s potential within regulatory limits.

Sarah Patel (Real Estate Attorney, Patel & Associates). Legally, the number of ADUs permitted on a single property is dictated by municipal code and state laws, which have been evolving to address housing shortages. Some states have enacted legislation to encourage multiple ADUs per lot, but restrictions remain in place to prevent overcrowding and maintain neighborhood character. Property owners should conduct thorough due diligence, including title review and local ordinance analysis, before initiating multiple ADU projects.

Frequently Asked Questions (FAQs)

How many ADUs can I legally build on my property?
The number of ADUs allowed depends on local zoning laws and property size. Most jurisdictions permit one primary ADU per lot, but some areas allow multiple units under specific conditions.

Do property size and zoning affect the number of ADUs I can build?
Yes, minimum lot size and zoning classifications significantly influence the allowable number of ADUs. Larger lots and certain zoning districts may permit additional units.

Are there restrictions on the total square footage of ADUs on a property?
Many municipalities impose maximum size limits for ADUs, either as a percentage of the primary dwelling or a fixed square footage, to control density and maintain neighborhood character.

Can I build both a detached and an attached ADU on the same property?
In some areas, regulations allow both an attached and a detached ADU on a single property, effectively enabling two separate units, subject to local ordinances and design standards.

Do local building codes and permits limit the number of ADUs?
Building codes and permit requirements can restrict the number of ADUs by enforcing safety, utility, and infrastructure standards, which may limit feasible unit counts.

Is it necessary to consult the city planning department before building multiple ADUs?
Yes, consulting the local planning department is essential to understand specific regulations, obtain necessary permits, and ensure compliance with all legal requirements for multiple ADUs.
Determining how many Accessory Dwelling Units (ADUs) you can build on your property depends on several factors including local zoning laws, lot size, and municipal regulations. Most jurisdictions have specific limits on the number of ADUs allowed per lot, often permitting one or two units, but these rules can vary widely. It is essential to consult your city or county planning department to understand the precise restrictions and requirements applicable to your property.

In addition to regulatory limits, considerations such as available space, utility connections, parking requirements, and neighborhood covenants also influence the feasibility of constructing multiple ADUs. Property owners should conduct thorough site assessments and possibly engage with professionals like architects or planners to maximize the use of their land while ensuring compliance with all relevant codes.

Ultimately, while building multiple ADUs can enhance property value and provide additional housing options, it is critical to navigate the legal framework carefully. Staying informed about local policies and obtaining the necessary permits will help ensure a smooth development process and avoid potential legal or financial complications.

Author Profile

Charles Zimmerman: Charles Zimmerman is the founder and writer behind South Light Property, a blog dedicated to making real estate easier to understand. Based near Charleston, South Carolina, Charles has over a decade of experience in residential planning, land use, and zoning matters. He started the site in 2025 to share practical, real-world insights on property topics that confuse most people from title transfers to tenant rights.

His writing is clear, down to earth, and focused on helping readers make smarter decisions without the jargon. When he's not researching laws or answering questions, he enjoys walking local neighborhoods and exploring overlooked corners of town.