Millbrae is one of the most convenient and well-connected cities in the Bay Area—perfect for homeowners looking to maximize space, increase home value, or create rental income through the addition of an Accessory Dwelling Unit (ADU). At Royalty Builders, we specialize in designing and building high-quality ADUs in Millbrae that are functional, stylish, and fully compliant with local and state building regulations.

Whether you’re considering a garage conversion, a backyard cottage, or a multi-generational in-law suite, our full-service design + build team has you covered from concept to completion.

Why Build an ADU in Millbrae?

Millbrae is located near SFO, Caltrain, and BART, making it one of the best-located suburbs on the Peninsula for commuters and renters alike. That makes ADUs a smart addition for homeowners looking to increase property usability and long-term value. Building an ADU in Millbrae can help you:

• Provide independent living space for aging parents or adult children

• Create passive rental income from long-term tenants

• Add a private home office or guest suite

• Improve your property’s resale value and flexibility

• Support sustainable, multi-generational living

Thanks to updated California ADU laws and Millbrae’s alignment with those policies, it’s now easier and faster to add an ADU than ever before.

Full-Service ADU Design + Build in Millbrae

At Royalty Builders, we simplify the ADU process by offering complete design + build services under one roof. You won’t need to juggle architects, contractors, or permit consultants—we take care of everything for you, while keeping you informed at every step.

Our ADU process includes:

• Feasibility Study: We evaluate your lot, utilities, and zoning to determine the best ADU options for your property.

• Architectural Design: Our in-house designers develop custom floorplans tailored to your lifestyle, goals, and property layout.

• Permitting: We handle all the paperwork and coordination with the City of Millbrae to secure fast approvals.

• Construction: Our experienced builders deliver quality workmanship, on time and on budget.

• Final Inspection & Support: After completing your ADU, we walk you through the space and ensure everything meets expectations.

Whether you’re building a rental unit or a family retreat, we ensure your ADU is designed to meet both your practical and aesthetic needs.

Types of ADUs We Build in Millbrae

Millbrae’s mix of older and newer homes provides great flexibility for different types of ADUs. We offer:

• Detached ADUs: Fully independent backyard cottages or studios for guests or renters

• Attached ADUs: Extensions of your existing home that offer privacy and convenience

• Garage Conversions: Transform your unused garage into a modern, livable space

• Above-Garage Units: Build up instead of out—perfect for maximizing small lots

• Junior ADUs (JADUs): Interior conversions under 500 sq. ft. that make the most of your existing footprint

We’ll help you determine the best solution based on your lot, budget, and intended use.

How Much Does It Cost to Build an ADU in Millbrae?

ADU costs in Millbrae vary depending on the size, structure type, finishes, and complexity. On average, here’s what you can expect:

• Garage Conversions: $130,000 – $180,000

• Attached ADUs: $200,000 – $350,000

• Detached ADUs: $250,000 – $400,000+

Your final investment will depend on:

• Property conditions and access

• Design and square footage

• Interior features and upgrades

• Utility connections and improvements

• Permitting and site work

At Royalty Builders, we offer detailed, transparent estimates to help you plan confidently and avoid cost surprises.

ADU Permit Process in Millbrae

Millbrae has made the permitting process for ADUs much more efficient, aligning with state mandates like AB 68 and SB 9. We handle everything related to city approvals so you don’t have to worry about red tape.

Our permit services include:

• Preparing and submitting architectural plans

• Managing communication with city planning and building departments

• Addressing any plan check corrections or zoning concerns

• Ensuring compliance with setbacks, height limits, parking rules, and design standards

We stay up to date with Millbrae’s evolving ADU regulations to get your project approved quickly and smoothly.

Frequently Asked Questions – ADU Services in Millbrae

Q: What’s the typical timeline for an ADU project in Millbrae?
A: Most projects take 6–10 months, depending on the size and type of ADU. This includes design, permitting, and construction.

Q: Will I need additional parking for my ADU?
A: In many cases, no. Millbrae often waives additional parking requirements if you’re near public transit, which many homes are.

Q: Can I rent out my ADU in Millbrae?
A: Yes! ADUs can be rented to long-term tenants, and the city allows owner-occupied and rental uses alike.

Q: Can I include a kitchen and bathroom in my ADU?
A: Yes. Your ADU can be fully self-contained, with its own kitchen, bath, and living area.

Q: What size ADU can I build in Millbrae?
A: You can build up to 1,200 sq. ft., depending on your lot size and type of ADU. We’ll help you design within the allowable limits.

Why Choose Royalty Builders for Your Millbrae ADU?

• 🏡 Local Bay Area Experts with knowledge of Millbrae’s permitting and zoning

• 🛠 All-In-One Team – Architects, contractors, and permit specialists under one roof

• ✅ Transparent Pricing and detailed project estimates

• 🧱 High-Quality Construction using durable, energy-efficient materials

• 📝 Custom Designs that blend with your home’s architecture

• 🌟 Satisfied Clients throughout the Peninsula and beyond

We make it easy for Millbrae homeowners to build smart, beautiful, and fully legal ADUs that improve quality of life and increase property value.

Ready to Build Your ADU in Millbrae?

Whether you’re building a guest house, a home office, or a rental unit, Royalty Builders is your trusted partner for ADU construction in Millbrae. Contact us today for a free consultation and let’s explore what’s possible on your property.

Call us today and schedule a free consultation.