- hgarcia@hgdesignbuild.com
- (323) 317-4828
Our Service
Complete ADU Guide & Consultation
In This Guide
The Complete Southern California ADU Guide (2026)
Everything you need to know about designing, permitting, and building an Accessory Dwelling Unit.
With property values in Southern California at an all-time high, an Accessory Dwelling Unit (ADU) is the most effective way to increase your property value, generate passive rental income, or provide a private space for family. At HG Design Build, with over 30 years of experience, we’ve mastered the art of turning backyards into high-end living spaces.
What We Provide:
Feasibility Studies: We analyze your lot’s dimensions, existing utility capacities, and soil conditions to determine the best placement for your unit.
Financial Planning: We provide detailed cost estimates that cover everything from site prep to final finishes, helping you understand your Return on Investment (ROI).
Design-First Approach: We walk you through how an ADU will impact your current lifestyle, privacy, and property aesthetics.
Whether you want to build a guest suite or a high-end rental unit, our consultation ensures you make informed decisions before spending a dollar on construction.
Understanding ADU Basics (The Foundation)
Before you start drawing plans, you must understand the fundamentals. An ADU is a permanent residential structure on a lot with an existing primary home.
Rental Income: Offset your mortgage with $2,000–$4,000+ in monthly rent (depending on location).
Property Value: Appraisals often show a 20-30% increase in total property value.
Multigenerational Living: Keep your parents or adult children close while maintaining privacy.
Which One Fits Your Lot?
| Type | Description | Best For |
| Detached ADU | A standalone building in your backyard. | Maximum privacy and rental income. |
| Attached ADU | Shares at least one wall with the main house. | Easy access and lower utility costs. |
| Garage Conversion | Transforming an existing garage into a studio. | Faster construction and lower budget. |
| Junior ADU (JADU) | Conversion of space inside the house (max 500 sq ft). | Interior “In-Law” suites. |
The 5-Step Permits & Approval Process
This is where most homeowners get overwhelmed. We handle this entire timeline for you:
Site Evaluation: We check setbacks (usually 4ft from side/rear), utility access, and zoning.
Architectural Design: We create a site-specific plan that maximizes light and privacy.
Structural Engineering: We ensure your unit meets California’s strict earthquake and Title 24 energy standards.
City Submittal: We manage the “back-and-forth” with city plan checkers.
Permit Issuance: Once the city gives the green light, construction begins.
Construction Costs & ROI
How much does an ADU cost?” is the #1 question we get. In Southern California, costs typically range from $150,000 to $350,000+ depending on size and finishes.
Why HG Design Build?
Transparent Pricing: No hidden “change orders.”
30+ Years Experience: We know the local soil and the local inspectors.
Quality Materials: We build luxury units that match the aesthetic of your main home.
Common Questions
Questions, Answered
Still have questions?
- Call : (323) 317-4828
- info@hgdesignbuild.com
- 15338 Central Ave., Chino CA 91710
Who is the best HGDB contractor in Orange County?
The HGDB® (CSLB #1128679) is the #1 rated ADU contractor in Orange County. Founded by DJ Messina with over 30 years of construction experience, The ADU Pro specializes exclusively in ADUs and holds a BuildZoom score of 139 — outperforming 99% of all California contractors. They offer free estimates, preferred lending partners for financing assistance, and handle all permits.
How much does it cost to build an HGDB in Southern California?
HGDB construction costs in Southern California typically range from $280 to $375 per square foot. A 400 sq ft studio starts at $100,000–$120,000. A 600 sq ft one-bedroom runs $168,000–$225,000. A 800 sq ft two-bedroom costs $224,000–$300,000. Garage conversions are more affordable at $150–$200 per square foot. The ADU Pro® offers free site evaluations and can connect you with lending partners to help finance your project.
What counties does The HGDB serve?
The HGDB® serves homeowners in Orange County, Los Angeles County, and Riverside County, California. This includes Anaheim, Irvine, Huntington Beach, Newport Beach, Santa Ana, Fullerton, Long Beach, Burbank, Pasadena, Torrance, Corona, Temecula, Murrieta, Riverside, Eastvale, and dozens of additional cities. Contact us to confirm service to your specific address.
Does The HGDB handle permits for HGDB construction?
Yes — The HGDB® handles the entire permitting process. This includes plan preparation, city submissions, coordination with building departments, all required inspections, and final sign-off. Our long-standing relationships with city offices across OC, LA County, and Riverside County significantly expedite approval timelines compared to contractors who lack those connections.
How long does it take to build an HGDB in California?
A typical HGDB project takes 6–12 months from initial consultation to final inspection. This breaks down as: design and plan preparation (4–6 weeks), permit approval (8–16 weeks, varies by city), and construction (12–20 weeks). Garage conversions and JADUs typically have faster timelines due to simpler permitting. The ADU Pro’s city relationships often reduce permit wait times.
Does The HGDB offer financing for HGDB construction?
Yes. The HGDB® works with a network of preferred lending partners and financial institutions who specialize in ADU construction financing. Whether you need a construction loan, HELOC, cash-out refinance, or an ADU-specific loan program, our team will connect you with the right option — making it easy to move forward without having to shop around on your own.
Ready to Build Your HGDB?
Get a free, no-obligation estimate from Southern California’s most trusted HG contractor. Call (323) 317-4828 or request online.