SI United Construction provides construction services for almost every combination of ADU and other accessory structures. Whether is it a simple detached ADU, garage conversion ADU, multiple buildings through SB9, or any other combination, our years of construction experience will help you avoid common pitfalls and guide your build.
Most importantly, our knowledge helps you maximize the return on your investment while not compromising on the privacy of your main home.
Our flat fee ADU and JADU services often include the following:
Attached ADU (Accessory Dwelling Unit):
• Convert part of an existing home (garage, basement, or interior space) into a permitted ADU for rental income or other uses.
• Ensure code-compliant fire separation, soundproofing, and private entry.
• Extend HVAC, plumbing, and electrical systems while maintaining energy efficiency.
• Add additional space to an existing home to build a newly attached ADU for rental income or other uses.
• Match exterior materials and design to blend with the existing structure.
• Manage inspections, utility hookups, and final certificate of occupancy.
Detached ADU (Accessory Dwelling Unit):
• Construction of entirely new, standalone ADU for rental income, multigenerational living, or other uses.
• Site preparation for new foundation, utilities, and access.
• Handle foundation, framing, roofing, and all structural components.
• Install full kitchens, bathrooms, and laundry areas with separate utility connections.
• Coordinate all permits, Title 24 requirements, and zoning compliance.
• Design for privacy and seamless integration with landscaping and access paths.
JADU (Junior Accessory Dwelling Unit):
• Convert existing space (typically a bedroom or portion of the home) into a compact, code-compliant unit.
• Compliance with California JADU codes, including shared bathroom and kitchenette requirement.
• Provide electrical upgrades, insulation, and finishes for comfort and safety.
• Ideal for college students, in-laws, or flexible-use private space.
Garage Conversion:
• Evaluate existing garage for ADU conversion.
• Handle all structural upgrades, including slab reinforcement, framing, and insulation.
• Provide electrical upgrades, insulation, and finishes for comfort and safety.
• Coordinate seismic upgrades, insulation, waterproofing, and ventilation as needed.
• Match exterior materials and design to blend with the existing structure.
• Manage inspections, utility hookups, and final certificate of occupancy.
Why Choose Us
- Hire an expert in zoning requirements. Not only does knowledge in zoning laws streamline the permitting and build process, it also allows our firm to help maximize the potential size and use of the build, increasing overall return on investment.
- Design for functionality and privacy. ADUs are often compact, so it’s important to maximize every square foot. Focus on creating a layout that’s not only efficient but also comfortable. Additionally, consider the privacy of both the ADU occupants and those in the main house, especially when designing entrances, windows, and shared spaces.
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Specializing in the design and construction of Accessory Dwelling Units (ADUs), our team helps homeowners maximize their property’s potential and ROI. Whether you’re building an ADU for extra income, a guest house, or a private living space, we handle every detail from permitting to final touches. We prioritize smart design that enhances functionality, maintains privacy, and ensures a seamless integration with your property. With efficient timelines and high-quality construction, your ADU will add long-term value.
“We wanted a detached ADU for some additional passive income. Not only did SI United Construction manage the entire process seamlessly, they really emphasized changes that added privacy. Now we have a great source of revenue and we still kept the privacy we had grown accustomed to.”
– Homeowner
“I had two awkward interior storage spaces holding left over junk from my old tenants. SI United Construction immediately saw the potential to convert the space into two separate one-bedroom apartments under the new ADU law. Now those spaces are fully functioning apartments with separate entrances – beautifully finished and immediately leased. It was a huge ROI.”
– Landlord
Schedule a FREE estimate today so we can discuss how our flat-fee options can save you time and money.