Expand Your Living Space with an ADU
Accessory Dwelling Units (ADUs) offer a versatile and cost-effective way to expand your living space, increase property value, and create rental income. Whether you’re looking to house extended family, generate passive income, or add a home office, Sightline Builders specializes in crafting high-quality ADUs tailored to your needs.

What is an ADU?
An ADU is a secondary housing unit on a residential lot that can be either attached to or separate from the main home. ADUs come in various forms:

Detached ADU:
A standalone structure, providing the most privacy and flexibility.
Attached ADU:
Built as an extension of the main home with a separate entrance.
Garage Conversion ADU:
Transforming an existing garage into a livable space.
Junior ADU (JADU):
A smaller unit within the main house, often utilizing existing square footage.
Find Out What You’re Eligible to Build
For Sonoma and Napa Counties, you can look up your address to determine what you’re eligible to build. The information provides your jurisdiction, recorded use, zone, number of dwellings, approximate lot size, and approximate building footprint for your property. It also summarizes what possible ADU options or ADU combinations could be available to build on your property. When starting your process, contact us to begin the conversations with the local building department and develop preliminary plans.
Use the Sonoma County ADU Calculator to estimate what type of ADU you can build based on your property characteristics.


ADU Regulations & Permitting in Northern California
Navigating local regulations is essential to a successful ADU project. Sightline Builders stays up to date on city and county zoning laws, including:
- Minimum lot size requirements
- Setback and height restrictions
- Maximum allowable ADU size
- Utility connections and parking requirements
- Permit costs and approval timelines
Our team will guide you through these details to ensure a smooth approval process.
Understanding and navigating local regulations is essential for a successful ADU project. Each city and county has unique requirements that affect your project’s size, location, and design.
State Regulations
California has passed legislation to encourage ADU development, making it easier than ever to build. Familiarize yourself with these state laws to understand your rights and opportunities.
Local Ordinances
Regulations vary depending on your location. Below are links to ADU guidelines for Sonoma County and nearby cities:
- Sonoma County: Sonoma County ADU Guidelines
- Santa Rosa: Santa Rosa ADU Guidelines
- Sebastopol: Sebastopol ADU Guidelines
- Petaluma: Petaluma ADU Guidelines
- Cotati: Cotati ADU Guidelines
- Rohnert Park: Rohnert Park ADU Guidelines
- Windsor: Windsor ADU Guidelines
- Healdsburg: Healdsburg ADU Guidelines

Pro Tip: Each property has unique factors—such as zoning, lot size, and setbacks—that influence what’s possible. Consulting your local planning department or working with our team ensures your project complies with all regulations.
The Process: From Concept to Completion
Building an ADU involves multiple steps, but Sightline Builders is here to simplify the process. Here’s what you can expect:
Initial Consultaion: We assess your property, discuss your goals, and provide a feasibility analysis.
Design & Planning: Our team works with you to create a design that fits your needs, aligns with zoning regulations, and optimizes space.
Permitting: We handle the permit submission process, ensuring compliance with local building codes and ordinances.
Construction: Our experienced team manages every aspect of construction with precision and efficiency.
Final Inspection & Handover: We ensure that all work meets quality and safety standards before handing over your completed ADU.
ADU Costs & Financing Options
Understanding the costs associated with an ADU is crucial for planning. The total investment depends on factors such as size, design complexity, and site conditions. Sightline Builders provides transparent pricing and cost breakdowns so you can make an informed decision.
Potential ADU Costs
- Garage Conversion: $75,000 – $150,000
- Attached ADU: $150,000 – $300,000
- Detached ADU: $200,000 – $400,000+

Financing Your ADU
Many homeowners utilize financing options such as:
- Home equity loans or HELOCs
- Construction loans
- ADU-specific state grant programs
- Cash-out refinancing
Our team can help you explore financing opportunities to make your ADU project feasible.
Design & Customization Options
Every homeowner has unique needs, and your ADU should reflect that. We offer:
- Open-concept layouts
- Energy-efficient appliances and materials
- Smart home technology integration
- Aging-in-place features for accessibility
- Custom cabinetry, finishes, and fixtures
What Our Clients Say
“Our home was built by Sightline. It’s an ADU about 750 sf. I found Sightline to be extremely knowledgeable and professional. The finished product is excellent. It was fun working with Jason and Sarah in planning all the way through to the finished product. We could bounce ideas, get suggestions, and make minor changes without hassle and controversy. I would definitely use Sightline again if the situation ever arises.” – Randy M.
FAQs About ADUs
How long does it take to build an ADU?
Most ADU projects take 6-12 months, depending on design complexity and permitting timelines.
Do I need additional parking for an ADU?
Regulations vary by city, but many areas no longer require additional parking for ADUs.
Can I rent out my ADU?
Yes! ADUs can be used as long-term rentals, guest homes, or short-term rentals (subject to local ordinances).
Check out our ADU Frequently Asked Questions link below for more information.
Start Your ADU Project Today
If you’re looking for an ADU Builder in Petaluma, Santa Rosa, Sebastopol, or the Sonoma County area, Sightline Builders is here to simplify the process, from design to construction. Our ADU contractors are well versed in local regulations, permitting, and innovative designs to help you create a functional and beautiful ADU that meets your needs and budget.
If you’re ready to explore adding an ADU to your property, Sightline Builders is here to help. Contact us today for a free consultation!