Building an ADU in San Diego: Key Insights for Homeowners

Building Your San Diego ADU: A behind-the-scenes look at the construction process, from blueprints to completion, adding value and functionality to your property.

Curious about adding an Accessory Dwelling Unit (ADU) to your San Diego property? You’re in good company. From La Mesa to Lemon Grove, homeowners are embracing ADUs to create extra space, house families, or earn rental income—all while boosting property value. At H&M Building Services LLC, we’ve built dozens of ADUs across San Diego County, and we’re here to share the essentials you need to know before breaking ground. Welcome to ADUs 101—let’s get you started!

What Exactly Is an ADU?

An Accessory Dwelling Unit (ADU) is a self-contained living space in your backyard, offering flexibility, comfort, and functionality.

An ADU—often called a granny flat, in-law suite, or backyard cottage—is a secondary living unit on your property. It could be a detached studio, a garage conversion, or an attached apartment, complete with its own kitchen, bathroom, and entrance. Thanks to California’s 2025 ADU laws, San Diego makes it easier than ever to add one, whether you’re in Spring Valley or Rancho San Diego.

ADUs: The perfect solution for extra space—welcoming guests, housing aging parents, or giving young adults a place of their own while staying close to family.

5 Must-Knows Before You Build

San Diego ADU Zoning Made Simple: Highlighted areas show eligible lots, while homeowners and architects review blueprints to ensure compliance with local regulations.

Zoning Rules: Most single-family lots qualify for an ADU—up to 1,200 square feet detached or 50% of your home’s size if attached. San Diego’s pre-approved plans cut red tape, but coastal areas (e.g., Pacific Beach) might have height limits. We’ll check your lot to confirm.

ADU Cost Breakdown: Understand the price range for detached units and garage conversions, including utilities, permits, and finishes, to plan your investment wisely.

Cost Breakdown: Expect $100K-$250K for a detached ADU, depending on size and finishes. Garage conversions run $70K-$150K. Factor in utilities (water, sewer) and permits—our detailed estimates keep it clear.

Contact Form

Modern San Diego ADU: A stylish, functional, and private living space seamlessly integrated into your backyard.

Design Flexibility: Want a sleek studio with a patio? A cozy one bedroom with skylights? ADUs can match your style and San Diego’s vibe—think big windows for that sunshine.

ADU Timeline: From permits to move-in, plan for 6-12 months. Faster approvals and efficient construction can have you settled in as quickly as five months!

Timeline: From permits to move-in, plan 6-12 months. City approval takes 2-4 months (faster with pre-approved designs), and construction runs 3-6 months. We’ve wrapped La Mesa ADUs in five months flat.

Explore your ADU financing options—cash, home equity loans, construction financing, or California’s ADU grants (up to $40K). We’re here to guide you every step of the way!

Financing Options: Cash is king, but home equity loans, construction financing, or California’s ADU grants (up to $40K) work too. We can guide you to local lenders.

Watch Out for These Traps

Permit Pitfalls: Skipping them risks fines or resale headaches. We handle every step.
Utility Costs: Hooking up power or sewer can add $10K-$20K—don’t skip the math!
Setback Rules: Most lots need a 4-foot buffer from fences—key in tight Spring Valley yards.

Why Trust H&M with Your ADU?

Building an ADU isn’t just construction—it’s navigating San Diego’s quirks, from codes to climate. Since 2017, H&M Building Services LLC has perfected the process: design, permits, and a flawless build, all in-house. Our owner, Carlos Herrera, brings decades of local expertise, and our Yelp reviews rave about our clear communication. We’re not here to sell you a unit—we’re here to build your solution.

Contact Form

Ready to Build Your ADU? Let’s Talk!

An ADU could transform your property—and your life—in 2025. Whether it’s extra income or a space for family, H&M Building Services LLC makes it simple, from concept to keys. Curious? Start with a no-pressure chat.

Call us at 858-609-7080, email contact@hmsandiego.com, or visit www.hmsandiego.com/contact-us to schedule your free consultation today. Let’s turn your San Diego lot into something special—reach out now!

Services