In a desirable and high-demand city like Foster City, maximizing the functionality and value of your property is key. Building an Accessory Dwelling Unit (ADU) offers the perfect opportunity to expand your living space, increase your home’s value, and generate rental income—all without needing to move or buy a new property.

At Royalty Builders, we help Foster City homeowners bring their ADU vision to life with expert design-build services, deep knowledge of local zoning codes, and a commitment to quality that shows in every detail.

Types of ADUs We Build in Foster City

Every property is unique—and so is every ADU we build. At Royalty Builders, we offer a variety of ADU options to suit different lot sizes, budgets, and homeowner needs.

We specialize in:

• Detached ADUs – Standalone backyard homes that offer full independence and privacy

• Attached ADUs – Seamless additions built onto the existing home, great for flexible family use

• Garage Conversions – Transforming underused garages into beautiful, fully livable units

• Above-Garage ADUs – Maximizing vertical space with studio or loft-style living

• Basement ADUs – Efficiently converting below-grade space into legal living areas

Our team helps you choose the design that delivers the most impact—with the least complexity.

Full-Service ADU Design + Build in Foster City

Royalty Builders offers a complete, end-to-end design-build solution, managing your ADU project from concept to completion under one roof. That means no dealing with multiple vendors or city offices—we handle it all for you.

Our comprehensive process includes:

• In-depth site analysis and zoning review

• Architectural design tailored to your home and goals

• Engineering and plan drafting

• All permitting and city approvals

• Complete construction and project management

• Final inspections and occupancy certification

From the first sketch to the final walk-through, you’ll enjoy total transparency, clear communication, and expert craftsmanship every step of the way.

How Much Does It Cost to Build an ADU in Foster City?

ADU pricing varies based on many factors, including size, type, complexity, and finishes. At Royalty Builders, we offer fair, transparent estimates so you know exactly what you’re getting—and what it will cost.

Typical cost ranges in Foster City:

• Garage Conversion: $120,000 – $180,000

• Attached ADU: $180,000 – $300,000

• Detached ADU: $200,000 – $350,000+

• Above-Garage ADU: $220,000 – $350,000+

We also work with you to explore financing options and plan your build according to your budget—without compromising on quality or code compliance.

Permits for ADU Construction in Foster City – What You Need to Know

Foster City has adopted California’s ADU-friendly laws, but local permitting can still be a complex process. That’s where we come in. Our team is well-versed in Foster City zoning codes, lot size requirements, setbacks, height limits, and utility connections.

We handle:

• Permit applications

• Architectural and engineering plan submissions

• Revisions and city correspondence

• Scheduling inspections

• Ensuring code compliance throughout construction

Our permitting experts make the process smooth, so you don’t lose time or sleep over red tape.

Why Build an ADU in Foster City?

Foster City is a peaceful, family-friendly community known for its beautiful waterfronts, excellent public schools, and proximity to major tech hubs. It’s a place where families grow, professionals thrive, and property values remain strong.

Building an ADU in Foster City is a smart investment that offers multiple benefits:

• 💰 Rental income to help with the rising cost of living

• 🏠 Private space for multigenerational living or out-of-town guests

• 🧑‍💻 Home office, gym, or creative studio separate from the main house

• 📈 Increased property value in a highly competitive real estate market

Thanks to California’s streamlined ADU regulations and Foster City’s support for smart development, homeowners now have more flexibility than ever to make the most of their land.

Why Choose Royalty Builders for Your Foster City ADU?

We’re not just builders—we’re your trusted partners throughout the entire ADU journey. Royalty Builders is known across the Bay Area for delivering beautiful, code-compliant ADUs on time and on budget.

Why Foster City homeowners choose us:

• ✅ Local expertise with Foster City building regulations

• ✅ In-house design-build team for full control and accountability

• ✅ Custom solutions, not cookie-cutter designs

• ✅ Clear, upfront pricing with no hidden surprises

• ✅ Hands-on project managers and consistent updates

• ✅ Dozens of satisfied homeowners throughout San Mateo County

We care as much about your project as you do—and we don’t stop until it’s done right.

Frequently Asked Questions – ADUs in Foster City

Q: How big can my ADU be in Foster City?
A: Most ADUs can be up to 800–1,000 sq. ft., depending on your lot size and zoning. We’ll help determine what’s possible on your property.

Q: Will I need to provide additional parking?
A: In many cases, ADUs are exempt from parking requirements—especially if you’re near transit or converting an existing structure.

Q: How long does it take to build an ADU?
A: From design to move-in, most projects take 6–10 months, depending on scope and permitting.

Q: Can I rent my ADU?
A: Yes. ADUs can be used as long-term rentals in Foster City. We’ll ensure your unit meets all applicable rental codes.

Contact Royalty Builders – Let’s Build Your Foster City ADU

Are you ready to expand your property with a beautiful, functional ADU? Whether you’re looking to house a loved one, earn rental income, or increase your home’s value, Royalty Builders is here to help.

📞 Contact us today and schedule your free ADU consultation in Foster City.

Let’s bring your vision to life—on your timeline and on your terms.