ADU Buiders

Expert San Marcos ADU Builders for a Successful Project

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11 min read

Ensure the success of your ADU with an experienced builder in San Marcos.


The trend of building Accessory Dwelling Units (ADUs) in San Marcos, California, has gained momentum as homeowners recognize the potential to enhance their property value, accommodate extended family, or generate rental income. Partnering with the right ADU builders and understanding the local construction and rental processes are crucial to ensure a successful and compliant ADU project. This resource page aims to provide essential information to guide you through the nuances of ADU development in San Marcos, emphasizing the importance of choosing experienced builders like Better Place Remodeling for a seamless experience.

Essential ADU Rules for San Marcos

What you can build

  • Maximum size

    Single-family properties in San Marcos allow one ADU and one JADU, with ADUs up to 850 sq ft for one bedroom and 1000 sq ft for multiple bedrooms. Multifamily properties can add two detached ADUs and convert specific non-livable spaces.
  • Side / rear setbacks

    Detached ADUs require a four-foot setback from side and rear property lines. Converted ADUs don't need extra setbacks if they meet fire and safety standards.
  • Two story

    Allowed above garages, subject to height and zoning rules
  • Building separation

    Mandated 10-foot separation between ADUs and existing structures.

Permitting timeline

  • Standard

    4-6 months.
  • Coastal

    Not required.

Choosing the Right ADU Builder in San Marcos

Selecting a builder experienced in ADUs is pivotal for navigating San Marcos’s specific zoning laws, design considerations, and regulatory landscape efficiently. Better Place Remodeling stands out as the premier choice, offering an in-house, one-stop-shop solution for ADU projects. Our expertise in local zoning knowledge, design aptitude, and proficiency in managing city regulations ensures a streamlined process from conception to completion, making Better Place Remodeling the best choice for ADU construction in San Marcos.

San Marcos ADU Construction Process

The construction process for an ADU in San Marcos involves several key phases:

  • Initial Consultation and Feasibility Study

Assessing property eligibility, zoning requirements, and project viability.

  • Design and Planning

Creating a design that meets the homeowner’s needs while adhering to local codes.

  • Permitting

Submitting detailed plans to the city for approval, including addressing any required surveys or reports.

  • Construction

Starting with site preparation, followed by foundation laying, framing, and installation of utilities, roofing, and interiors.

  • Inspection and Completion

Undergoing city inspections to ensure compliance with building standards before final turnover.

This overview highlights the importance of compliance at every step, ensuring a smooth journey from concept to completion.

Building Your ADU in San Marcos

The number of Accessory Dwelling Units (ADUs) allowed in San Marcos varies based on property type and zoning regulations. Single-family properties typically permit one ADU per property, with potential for a Junior ADU (JADU) if owner-occupied. Properties with multiple dwelling units may accommodate up to two detached ADUs and convert habitable and non-habitable spaces into ADUs.

Yes, in San Marcos, ADUs can be rented out, but only for periods longer than 30 days, prohibiting short-term rentals. Importantly, there is no owner-occupancy requirement for ADU applications submitted from January 1, 2020, to January 1, 2025, facilitating property owners’ ability to rent out their ADUs without the need to reside on the property themselves.

In San Marcos, multifamily properties can have up to two detached ADUs. Existing multifamily structures can convert non-livable spaces into attached ADUs, capped at 25% of existing units. Detached ADUs can reach up to 850 sq ft for one bedroom or 1000 sq ft for multiple bedrooms, with a maximum height of 16 feet and typically limited to one story unless above a garage. Architectural compatibility with the primary dwelling is required. These regulations aim to expand housing options while complying with local zoning and building standards.

ADU Size & Building Constraints in San Marcos

Detached ADUs in San Marcos are subject to size limitations: up to 850 square feet for a one-bedroom unit and up to 1000 square feet for units with two or more bedrooms. Detached ADUs up to 800 square feet are exempt from lot coverage requirements.

The height restriction for detached ADUs in San Marcos is generally limited to one story, not exceeding 16 feet. However, for detached ADUs located above a garage, there are specific provisions allowing for two-story construction, subject to zoning area height limits.

Yes, two-story ADUs are permissible in San Marcos under certain conditions, specifically when constructed above a garage. This arrangement allows for additional living space while adhering to the city’s height and zoning regulations.

Information regarding the allowance of roof decks on ADUs in San Marcos is not explicitly provided in the regulations. Property owners interested in adding roof decks to ADUs are advised to consult with the San Marcos city planning department for guidance on current policies and specific project requirements.

The maximum size for attached ADUs in San Marcos is either 50% of the existing living area of the primary dwelling or a maximum of 1,200 square feet, offering flexibility in the development of attached living spaces.

In San Marcos, ADUs must comply with specific exterior requirements, including setbacks of five feet from side and rear lot lines for detached ADUs, a height limit of 16 feet (with allowances for two-story ADUs over garages), and architectural compatibility with the primary dwelling. These requirements ensure that ADUs integrate well with the primary residence and maintain the aesthetic coherence of residential neighborhoods.

Renting Your ADU in San Marcos

Renting out an ADU in San Marcos offers homeowners a valuable opportunity to generate income or provide housing for family members. Understanding local market dynamics, rental income potential, and landlord responsibilities is crucial. Homeowners must consider utility provisions and the potential for separate mailing addresses to ensure the ADU’s rental readiness. Consulting with experienced builders and the city planning department can provide insights into optimizing your ADU for rental purposes while complying with local regulations.

Neighborhoods: Barham Discovery Community, Felicita, Lake Hodges, Lake San Marcos, Leucadia, Palomar Estates, San Elijo, San Marcos, Vista Valley, Vineyard, West Ridge.


Calculate Your ADU Cost in San Marcos

Curious about the cost of your ADU in San Marcos? Find out quickly with our interactive calculator. This tool is designed to give you a rough estimate.

Attached ADU

0 sqft

Estimated Cost


*The costs we are calculating here are an average for time and materials. This calculator is meant to provide an estimate to educate you on the ADU building process, please note that this is not a final quote.

Detached ADU

0 sqft

Estimated Cost


*The costs we are calculating here are an average for time and materials. This calculator is meant to provide an estimate to educate you on the ADU building process, please note that this is not a final quote.

Garage ADU

0 sqft

Estimated Cost


*The costs we are calculating here are an average for time and materials. This calculator is meant to provide an estimate to educate you on the ADU building process, please note that this is not a final quote.
Reach out


Building and renting out an ADU in San Marcos presents a promising avenue for homeowners to maximize their property’s value and functionality. Partnering with Better Place Remodeling, a builder experienced in local ADU projects, ensures a smooth, compliant, and efficient development process. By understanding the key rules, engaging in the detailed construction process, and considering rental logistics, homeowners can successfully navigate the ADU journey. We encourage you to leverage this information and consult with both experienced ADU builders and San Marcos’s planning department to realize the full potential of your ADU project.


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