ADU Regulations at a Glance
Brentwood ADU Rules & Regulations
California State ADU Laws
California has some of the most progressive ADU legislation in the country. Recent laws including AB 68, SB 13, AB 881, AB 2221, and SB 897 have significantly streamlined the ADU approval process and reduced barriers for homeowners across the state, including in Brentwood.
Key California ADU Regulations:
- Size Limits: Detached ADUs can be up to 1,200 sq ft. Attached ADUs can be up to 50% of the primary dwelling or 1,200 sq ft, whichever is less. Junior ADUs (JADUs) can be up to 500 sq ft within the existing home footprint.
- Setbacks: 4-foot side and rear setbacks for new detached ADUs. Existing structures being converted (like garages) can maintain non-conforming setbacks.
- Height: Up to 16 feet for standard detached ADUs, 18 feet within a half-mile of transit, and up to 24 feet for two-story ADUs in qualifying zones.
- Parking: No additional parking required if the property is within a half-mile of a public transit stop. Otherwise, one space may be required. Tandem parking and mechanical lifts are allowed.
- Owner Occupancy: No owner-occupancy requirement for ADUs. Owner occupancy is required only for properties with a JADU.
- Approval Timeline: Cities must approve or deny ADU applications within 60 days.
- Impact Fees: ADUs under 750 sq ft are exempt from impact fees. Larger ADUs may be subject to proportionally reduced fees.
- Multiple ADUs: Single-family lots can have one ADU plus one JADU. Multi-family properties can add up to two detached ADUs or convert up to 25% of existing non-livable space.
Brentwood-Specific ADU Considerations:
As a neighborhood within the City of Los Angeles, Brentwood follows the City's ADU ordinance (LAMC Section 12.22 A.31), which implements state law with some local additions:
- Local Zoning: R1 and RE zones with large minimum lot sizes. Brentwood-Pacific Palisades Community Plan area.
- Lot Characteristics: Brentwood properties typically have lot sizes of 10,000-30,000 sq ft, which provides ample room for most ADU configurations.
- Common ADU Types: Detached luxury ADUs, Guest house conversions, Pool house conversions, Home office/studio ADUs are the most popular ADU approaches in Brentwood.
- Garage Conversions: Multi-car garages are standard but rarely converted due to vehicle storage needs. New detached construction on large lots is preferred.
- Transit Access: While Brentwood's transit score of 38 reflects more limited transit, properties near major bus routes may still qualify for parking exemptions.
- Rental Market: Moderate-High (specialized market) demand with ADU rents typically ranging from $3,500-$6,000/month for studio/1BR luxury ADU.
- Fire Zone: Some properties in Brentwood may be within a Very High Fire Hazard Severity Zone (VHFHSZ), which imposes additional building requirements for fire-resistant materials, defensible space, and emergency access.
These regulations reflect the City of Los Angeles' commitment to increasing housing options while addressing Brentwood's unique neighborhood characteristics. GatherADU specializes in navigating these regulations to design and build ADUs that comply with all local, city, and state requirements while maximizing value for homeowners.
Recent ADU Law Updates Affecting Brentwood
California continues to update its ADU laws to further streamline the process and remove barriers for homeowners. Recent legislation that benefits Brentwood property owners includes:
- AB 2221 (2023): Clarified that ADUs cannot be rejected based on the existing primary dwelling's non-conformity with current zoning. This is particularly beneficial for Brentwood's older housing stock, where many homes may not fully conform to current zoning standards.
- SB 897 (2023): Increased height limits for ADUs, allowing up to 18 feet near transit and up to 24 feet for two-story ADUs in multi-family zones. Properties near transit stops in Brentwood may qualify for the increased height limits.
- AB 976 (2024): Made the prohibition on owner-occupancy requirements for ADUs permanent. Brentwood homeowners can rent both their primary home and ADU without living on the property.
- AB 434 (2024): Streamlined the ministerial approval process further, ensuring cities cannot impose unreasonable conditions on ADU applications.
ADU Permitting Tips for Brentwood Homeowners
Successfully navigating the ADU permitting process in Brentwood requires attention to several key areas:
- Pre-Submission Consultation: Before submitting plans, schedule a pre-review with LADBS or work with an experienced ADU builder like GatherADU who can identify potential issues early.
- Complete Documentation: Ensure your application includes all required documents including site plans, floor plans, elevations, Title 24 energy calculations, and structural calculations. Incomplete applications are the most common cause of delays.
- HOA Considerations: While California law prevents HOAs from outright prohibiting ADUs, some Brentwood properties may be in communities with CC&Rs that require design review. HOAs cannot unreasonably restrict ADUs but may have input on aesthetic elements.
- Utility Coordination: Contact DWP (water and power) and the LA Bureau of Sanitation early in the process to determine if any utility upgrades are needed for your Brentwood property.
- Timeline Management: The City must approve or deny your application within 60 days. If no decision is made within that period, your application is deemed approved under state law.
GatherADU has helped hundreds of Los Angeles homeowners navigate the ADU process, including many in the Westside area. Our team handles all aspects of design, permitting, and construction, ensuring your Brentwood ADU project proceeds smoothly from concept to completion. Call (323) 591-3717 for a free consultation.
Your Rights Under California Law
California law (AB 68, AB 881, SB 9, and subsequent legislation) guarantees your right to build ADUs. Cities cannot:
- Require owner-occupancy for ADUs permitted after 2020
- Require additional parking for ADUs near transit
- Charge impact fees for ADUs under 750 sq ft
- Deny ADUs that meet state minimum standards
- Impose lot coverage limits that prevent a 800 sq ft ADU
If you believe your ADU application is being unfairly denied, California HCD can intervene on your behalf.
This information is for informational purposes only and does not constitute legal advice. Consult a qualified attorney for legal guidance.
About Brentwood
Brentwood is a distinctive neighborhood within the City of Los Angeles, located in Los Angeles County, California. Brentwood is an affluent Westside neighborhood known for its leafy streets, upscale shopping, celebrity residents, and proximity to both the beach and the mountains. The area combines luxury living with a village-like commercial center, making it one of LA's most desirable residential communities. With a population of approximately 31,000 residents and a median household income of $145,000, Brentwood represents an affluent community within the greater Los Angeles metropolitan area.
The neighborhood encompasses several zip codes including 90049, and is situated in the Westside region of Los Angeles. Brentwood is surrounded by the neighborhoods of Bel Air, Pacific Palisades, Westwood, Santa Monica (city), creating a connected urban fabric of diverse communities. The area's geographic coordinates (34.0583°N, -118.4784°W) place it on the desirable Westside of Los Angeles.
Key landmarks and attractions in Brentwood include Getty Center, San Vicente Boulevard coral trees, Brentwood Country Mart, and Archer School for Girls. The area is known for its Mediterranean estates, Contemporary mansions, Ranch homes, with lot sizes typically ranging from 10,000-30,000 sq ft. The average home price in Brentwood is approximately $3,200,000, and the median monthly rent is around $3,800.
For homeowners considering an Accessory Dwelling Unit (ADU) in Brentwood, the neighborhood offers large lots provide ample space for luxury adu construction. Additionally, high property values justify premium builds with designer finishes. The moderate-high (specialized market) rental demand in the area, combined with rental prices ranging from $3,500-$6,000/month for studio/1BR luxury ADU, makes ADU construction a highly lucrative investment for property owners. Common ADU types in Brentwood include Detached luxury ADUs, Guest house conversions, Pool house conversions.
The local economy is driven by Real estate, Professional services, Luxury retail (Brentwood Country Mart, San Vicente shops), providing a diverse employment base that supports the rental market. The school district serving Brentwood includes LAUSD - includes Brentwood Science Magnet, plus prominent private schools (Brentwood School, Archer School), contributing to the area's appeal for families.
Transit options in Brentwood include Metro bus routes on San Vicente Blvd, Wilshire Blvd, Sunset Blvd, Big Blue Bus routes. The neighborhood has a walkability score of 52, a bike score of 56, and a transit score of 38, reflecting its more suburban or car-dependent character, though properties near bus routes may still qualify for transit-adjacent parking exemptions.
Brentwood's unique character, and moderate-high (specialized market) rental demand make it one of the most profitable location for ADU investment in Los Angeles. Whether homeowners are looking to generate rental income, create multigenerational living arrangements, or add a home office studio, an ADU in Brentwood offers substantial value.
More About Brentwood
Brentwood, California, is a neighborhood within the City of Los Angeles located in the Westside region of Los Angeles County. Brentwood is an affluent Westside neighborhood known for its leafy streets, upscale shopping, celebrity residents, and proximity to both the beach and the mountains. The area combines luxury living with a village-like commercial center, making it one of LA's most desirable residential communities.
Geography and History
Situated at coordinates 34.0583°N, -118.4784°W, Brentwood is positioned within the Westside area of Los Angeles. Developed in the 1920s as an upscale residential community, Brentwood has long been a favorite of entertainment industry executives and celebrities. The Brentwood Country Mart has been a community gathering place since 1948.
The neighborhood is bordered by Bel Air, Pacific Palisades, Westwood, Santa Monica (city), Sawtelle, creating a diverse tapestry of communities. Brentwood's zip code is 90049.
Local Economy
Brentwood's economy is driven by several key sectors that shape the neighborhood's character and employment landscape:
- Real estate: Real estate contributes to the local economy and provides employment opportunities for residents.
- Professional services: Professional services contributes to the local economy and provides employment opportunities for residents.
- Luxury retail: Luxury retail (Brentwood Country Mart, San Vicente shops)
- Entertainment industry: Entertainment industry contributes to the local economy and provides employment opportunities for residents.
- Education: Education (multiple private schools)
Housing Market and Real Estate
Brentwood's real estate market features Mediterranean estates, Contemporary mansions, Ranch homes, Cape Cod style, Tudor Revival, Modern custom homes. The average home price in Brentwood is approximately $3,200,000, making it one of the more premium neighborhoods in Los Angeles. Lot sizes typically range from 10,000-30,000 sq ft, providing generous space for ADU construction and outdoor living.
The median rent in Brentwood is approximately $3,800 per month, and the median household income is approximately $145,000. This rent-to-income ratio reflects a relatively balanced housing market, though ADUs still provide valuable additional rental inventory.
Transportation and Connectivity
Brentwood offers several transportation options for residents and commuters:
- Metro bus routes on San Vicente Blvd, Wilshire Blvd, Sunset Blvd
- Big Blue Bus routes
The neighborhood has a walkability score of 52 out of 100, a bike score of 56, and a transit score of 38. While transit access is more limited, many residents rely on personal vehicles, making parking an important consideration in ADU planning.
Schools and Education
Brentwood is served by LAUSD - includes Brentwood Science Magnet, plus prominent private schools (Brentwood School, Archer School). The neighborhood's educational institutions contribute to its family-oriented appeal and influence the rental market for ADUs, as families seeking quality schools often look for housing in the area.
ADU Regulations in Brentwood
As a neighborhood within the City of Los Angeles, Brentwood follows LA's ADU regulations, which align with and in many cases exceed California state law requirements. These regulations are designed to facilitate ADU development while addressing the city's critical housing needs.
- Zoning: R1 and RE zones with large minimum lot sizes. Brentwood-Pacific Palisades Community Plan area.
- Types of ADUs: Both attached and detached ADUs are permitted, as well as Junior ADUs (JADUs) of up to 500 sq ft created within the existing footprint of the primary home.
- Size Limits:
- Detached ADUs: Up to 1,200 sq ft regardless of lot size (as of January 2025)
- Attached ADUs: Up to 1,200 sq ft or 50% of the primary dwelling's living area, whichever is less
- JADUs: Up to 500 sq ft
- Height Restrictions: Detached ADUs can be up to 16 feet, or 18 feet if within a half-mile of a major transit stop. Two-story ADUs up to 24 feet are allowed in some zones.
- Parking: Ample private parking on most properties. San Vicente Blvd commercial area has metered parking. One additional parking space may be required unless the property is within a half-mile of a transit stop.
- Owner Occupancy: No owner-occupancy requirement for ADUs built under California state law. Owner occupancy is required only for JADUs.
- Setbacks: 4-foot side and rear setbacks for detached ADUs. ADUs converting existing structures (like garages) may maintain existing non-conforming setbacks.
- Impact Fees: ADUs under 750 sq ft are exempt from impact fees in the City of LA. ADUs 750 sq ft and above may be subject to proportional fees.
- Design Standards: ADUs must meet Los Angeles Building Code requirements. The City encourages ADU designs that complement the existing primary dwelling and neighborhood character.
ADU Opportunities Specific to Brentwood
Brentwood presents unique opportunities for ADU development based on its neighborhood characteristics:
- Large lots provide ample space for luxury ADU construction
- High property values justify premium builds with designer finishes
- Strong demand for ADUs as home offices, studios, and guest quarters
- Hillside properties require specialized construction
- Fire zone restrictions may apply to mountain-adjacent lots
- Some properties have existing guest houses or pool houses for conversion
Common ADU Types in Brentwood
Based on the neighborhood's lot sizes, zoning, and housing stock, the most common ADU types in Brentwood include:
- Detached luxury ADUs: Detached luxury ADUs are well-suited to Brentwood's neighborhood character and lot configurations.
- Guest house conversions: Converting existing guest houses or pool houses to legal ADUs leverages structures already on the property, often requiring less extensive construction.
- Pool house conversions: Converting existing guest houses or pool houses to legal ADUs leverages structures already on the property, often requiring less extensive construction.
- Home office/studio ADUs: Home office/studio ADUs are well-suited to Brentwood's neighborhood character and lot configurations.
ADU Rental Market in Brentwood
The rental demand in Brentwood is rated as Moderate-High (specialized market), with ADU rental prices typically ranging from $3,500-$6,000/month for studio/1BR luxury ADU. The strong rental demand ensures ADU owners can find quality tenants quickly, making ADU construction a sound financial investment.
Key factors driving Brentwood's rental market include:
- Average home price of $3,200,000 means many workers in the area cannot afford to buy, creating sustained rental demand
- Real estate and Professional services provide a stable employment base of potential tenants
- Growing transportation options improve accessibility for ADU tenants
- Proximity to Bel Air and Pacific Palisades extends the pool of potential tenants from surrounding areas
Cultural Landmarks and Unique Aspects
Brentwood is known for several unique features that define its character and appeal:
- San Vicente Boulevard iconic coral trees
- Brentwood Country Mart shopping
- Adjacent to Getty Center
- Village atmosphere in luxury neighborhood
Why Build an ADU in Brentwood?
Building an ADU in Brentwood offers homeowners a compelling combination of financial return and community benefit:
- Strong Rental Income: With rents of $3,500-$6,000/month for studio/1BR luxury ADU, an ADU can generate significant monthly income to offset mortgage costs or fund retirement
- Property Value Increase: ADUs typically add 20-35% of their construction cost to overall property value
- Housing Flexibility: An ADU can serve as rental income today and accommodate aging parents or adult children in the future
- Neighborhood Character: Brentwood's mediterranean estates housing stock and 10,000-30,000 sq ft lot sizes provide ample room for ADU construction without significantly impacting the property's character
- Community Need: Brentwood's moderate-high (specialized market) rental demand reflects a genuine need for more housing, and ADUs provide gentle density that benefits the entire community
ADU Construction Process in Brentwood
Building an ADU in Brentwood involves several key phases, each requiring careful planning and expertise. Here is a detailed overview of what homeowners can expect when building an ADU in this Los Angeles neighborhood:
Phase 1: Feasibility Assessment and Site Evaluation
The first step in building an ADU in Brentwood is determining what is possible on your specific property. This involves:
- Property Analysis: A thorough evaluation of your lot size (typical Brentwood lots are 10,000-30,000 sq ft), existing structures, setback requirements, and utility connections. Properties with larger lots in Brentwood typically have more flexibility in ADU placement and design.
- Zoning Verification: Confirming your property's zoning designation and any overlay zones that may apply. R1 and RE zones with large minimum lot sizes. Brentwood-Pacific Palisades Community Plan area.
- Soil and Topography Assessment: Standard soil testing ensures the foundation design is appropriate for your specific lot conditions.
- Utility Assessment: Evaluating existing sewer, water, electrical, and gas connections to determine what upgrades may be needed for the ADU.
Phase 2: Design and Architecture
ADU design in Brentwood should balance maximizing livable space with complementing the existing neighborhood character. Key design considerations include:
- Architectural Style: Brentwood's housing stock includes Mediterranean estates, Contemporary mansions, Ranch homes. ADU designs that reference these architectural elements create a cohesive property appearance.
- Floor Plan Optimization: Whether building a studio, one-bedroom, or two-bedroom ADU, efficient floor plans are essential. Open-concept layouts, built-in storage, and multi-functional spaces help maximize the impact of every square foot.
- Indoor-Outdoor Connection: Brentwood's generous lot sizes allow for private outdoor spaces, patios, or small yards adjacent to the ADU, significantly enhancing its appeal.
- Privacy: Window placement, landscaping, and ADU orientation should be carefully planned to provide privacy for both the ADU occupants and the primary residence.
- Natural Light: Strategic window placement, skylights, and clerestory windows help ADUs feel spacious and airy, reducing the need for artificial lighting during daytime hours.
Phase 3: Permitting
The City of Los Angeles has streamlined its ADU permitting process in compliance with state law. For Brentwood properties, the permitting process typically includes:
- Submitting plans to the Los Angeles Department of Building and Safety (LADBS)
- Plan check review (the city must approve or deny within 60 days under state law)
- Any required environmental or overlay zone reviews
- Building permit issuance
- Construction inspections at key milestones
- Final inspection and certificate of occupancy
The typical timeline from plan submission to permit approval in Los Angeles is 6-10 weeks, though actual timelines can vary based on project complexity and current department workload.
Phase 4: Construction
ADU construction in Brentwood typically takes 6-10 months depending on the type and size of ADU:
- Garage Conversions: Multi-car garages are standard but rarely converted due to vehicle storage needs. New detached construction on large lots is preferred. Garage conversions are often the fastest and most affordable ADU type, typically completing in 3-5 months.
- Detached New Construction: Building a new detached ADU from the ground up provides maximum design flexibility but requires the longest construction timeline, typically 6-10 months.
- Junior ADUs (JADUs): Converting existing space within the primary home into a JADU can often be completed in 2-4 months, as the basic structure already exists.
- Prefabricated/Modular ADUs: Factory-built ADU modules can significantly reduce on-site construction time, with installation and finishing work often completed in 2-4 months after the foundation is prepared.
ADU Cost Estimates for Brentwood
ADU construction costs in Brentwood vary based on the type of ADU, size, finishes, and site conditions. Here are approximate cost ranges that Brentwood homeowners can expect:
- Junior ADU (JADU) - Up to 500 sq ft: $80,000-$150,000. These conversions within the existing home footprint are the most affordable option.
- Garage Conversion - 400-600 sq ft: $100,000-$200,000. Converting an existing garage saves on foundation and framing costs.
- Detached ADU - 600-1,200 sq ft: $200,000-$450,000. New construction from the ground up offers the most flexibility but highest cost.
- Above-Garage ADU - 500-800 sq ft: $180,000-$350,000. Building above an existing or new garage maximizes lot usage.
- Prefabricated ADU - 400-1,200 sq ft: $150,000-$350,000. Factory-built modules offer consistent quality and faster timelines.
These estimates include design, permitting, construction, and standard finishes. Factors that can increase costs include challenging soil conditions, utility upgrades, and premium finishes. GatherADU provides detailed cost estimates specific to your Brentwood property during the free consultation phase.
ADU Financing Options for Brentwood Homeowners
Several financing options are available to Brentwood homeowners looking to build an ADU:
- Home Equity Line of Credit (HELOC): With Brentwood home values averaging $3,200,000, many homeowners have significant equity that can be leveraged to finance ADU construction. HELOCs offer flexible draw periods and competitive interest rates.
- Cash-Out Refinance: Refinancing your primary mortgage to pull out equity for ADU construction can be advantageous when interest rates are favorable, particularly for Brentwood properties with strong appreciation.
- Construction Loans: Short-term construction loans provide funding during the building phase and can be converted to permanent financing upon completion.
- CalHFA ADU Grant Program: California's Housing Finance Agency offers grants of up to $40,000 for pre-development costs (design, permits, soil tests) for ADU projects, available to qualifying homeowners in Brentwood.
- LA County ADU Accelerator Program: Los Angeles County has programs designed to assist homeowners with ADU development, including technical assistance and potential financial support.
- Personal Savings: For smaller projects like JADUs or garage conversions, personal savings may cover a significant portion of the construction cost.
The return on investment for an ADU in Brentwood is compelling: with ADU rents of $3,500-$6,000/month for studio/1BR luxury ADU, homeowners can expect to recoup their investment in 8-15 years through rental income alone, while also benefiting from increased property value.
ADU Design Ideas for Brentwood Properties
The architectural character of Brentwood inspires several ADU design approaches that complement the neighborhood while meeting modern living standards:
- Mediterranean estates Companion: ADUs designed to match the mediterranean estates architecture common in Brentwood create visual harmony between the primary dwelling and the accessory unit. Using similar materials, roof pitches, and design details ensures the ADU feels like a natural extension of the property.
- Modern Contrast: Some Brentwood homeowners opt for a contemporary ADU design that intentionally contrasts with the primary home's traditional architecture, creating visual interest while maintaining scale and proportion.
- Indoor-Outdoor Living: The Westside's temperate coastal climate is ideal for ADUs with strong indoor-outdoor connections, including large glass doors, decks, and garden access.
- Sustainable Design: Energy-efficient ADU designs are increasingly popular in Brentwood, incorporating solar panels, energy-efficient appliances, tankless water heaters, LED lighting, and drought-resistant landscaping. California's Title 24 energy code ensures all new ADUs meet high efficiency standards.
- Aging-in-Place Features: ADUs designed for multigenerational living may include single-story layouts, wider doorways, curbless showers, grab bars, and other universal design features that accommodate residents of all ages and abilities.
Frequently Asked Questions About ADUs in Brentwood
Q: How long does it take to build an ADU in Brentwood?
A: The total timeline from initial design to move-in typically ranges from 8-14 months for a detached ADU in Brentwood. This includes approximately 2-3 months for design and permitting, and 6-10 months for construction. Garage conversions and JADUs can be completed more quickly, often in 5-8 months total.
Q: Do I need to live on the property to build an ADU in Brentwood?
A: Under current California law, there is no owner-occupancy requirement for ADUs. You do not need to live in either the primary dwelling or the ADU. However, if you build a Junior ADU (JADU), owner occupancy in either the JADU or the primary home is required.
Q: Can I rent out my ADU on Airbnb or as a short-term rental in Brentwood?
A: Short-term rental regulations vary. The City of Los Angeles has specific rules regarding short-term rentals that may limit ADU use for platforms like Airbnb or VRBO. As of the most recent ordinance, ADUs used as short-term rentals must comply with the Home-Sharing Ordinance. Long-term rentals (30+ days) are generally unrestricted for ADUs.
Q: What is the maximum size ADU I can build on my Brentwood property?
A: Under California law, detached ADUs can be up to 1,200 sq ft regardless of your lot size. Attached ADUs can be up to 1,200 sq ft or 50% of the primary dwelling's living area, whichever is less. JADUs are limited to 500 sq ft. With Brentwood's typical lot sizes of 10,000-30,000 sq ft, most properties can accommodate a full-size 1,200 sq ft ADU.
Q: How much will an ADU increase my property value in Brentwood?
A: In the Brentwood market, ADUs typically add 20-35% of their construction cost to overall property value. With average home prices at $3,200,000 and ADU rental income of $3,500-$6,000/month for studio/1BR luxury ADU, the income-generating potential also contributes significantly to the property's appraised value, particularly when assessed using the income approach.
Q: Will I need to provide parking for my ADU in Brentwood?
A: Properties within a half-mile of a public transit stop are exempt from parking requirements. Properties farther from transit may need to provide one parking space for the ADU, though garage conversions are exempt from replacement parking requirements.
Neighborhood Comparison: Brentwood vs. Nearby Areas
Understanding how Brentwood compares to neighboring communities helps homeowners evaluate their ADU investment:
- Brentwood vs. Bel Air: Brentwood's average home price of $3,200,000 and lot sizes of 10,000-30,000 sq ft may be higher than Bel Air, while its moderate-high (specialized market) rental demand ensures strong ADU returns.
- Brentwood vs. Pacific Palisades: Both neighborhoods share Westside characteristics, but Brentwood's unique features including san vicente boulevard iconic coral trees distinguish its ADU market.
- Brentwood vs. Westwood: Brentwood's transit score of 38 and walkability of 52 reflects its distinct character, and each neighborhood offers different advantages for ADU investment.
Getting Started with Your Brentwood ADU Project
Brentwood's ADU regulations aim to support housing development while maintaining the neighborhood's unique character. With its san vicente boulevard iconic coral trees, brentwood country mart shopping, and moderate-high (specialized market) rental demand, Brentwood offers a compelling case for ADU construction. Whether you're building a detached backyard unit, converting a garage, or creating a junior ADU within your existing home, GatherADU can guide you through every step of the process — from design through permits to finished construction.
GatherADU has extensive experience building ADUs throughout the Westside area of Los Angeles, including in Brentwood and neighboring communities like Bel Air, Pacific Palisades, Westwood. Our team understands the unique requirements and opportunities that Brentwood properties present, and we can help you navigate local zoning rules, and the full permitting process.
Contact GatherADU today at (323) 591-3717 or visit gatheradu.com/contact to schedule your free ADU consultation and discover the potential of your Brentwood property.
Get Your Free Brentwood ADU Feasibility Report
Find out exactly what you can build on your property, estimated costs, and potential rental income.
Types of ADUs You Can Build in Brentwood
California law allows several types of accessory dwelling units on residential properties. Understanding your options helps you choose the best approach for your property and goals.
Detached ADU
A standalone structure built separately from your main house, typically in the backyard. Detached ADUs offer maximum privacy for both homeowners and tenants, with their own entrance, walls, roof, and complete living facilities. In Brentwood, detached ADUs can be up to 1,200 square feet and 16 feet tall. This option provides the most flexibility in design and placement, though it typically costs more than conversions due to new construction requirements.
- Max Size: Up to 1,200 sq ft
- Height: Up to 16 feet
- Setbacks: 4 ft from side/rear lines
- Best For: Maximum rental income, privacy
Attached ADU
An addition built onto your existing home, sharing at least one wall with the primary residence. Attached ADUs are often more cost-effective than detached units because they can leverage existing foundation, roof structure, and utility connections. They work well on properties with limited backyard space or where you want to minimize the visual impact of new construction. Many homeowners choose attached ADUs for aging parents who want proximity while maintaining independence.
- Max Size: Up to 1,200 sq ft
- Height: Matches main home
- Setbacks: Same as main structure
- Best For: Limited lot space, family housing
Garage Conversion ADU
Transform your existing garage into a complete living space. Garage conversions are often the most affordable ADU option in Brentwood because the basic structure already exists. You save on foundation, framing, and roofing costs while creating a valuable rental unit or family living space. California law prohibits cities from requiring replacement parking when you convert a garage to an ADU, making this option particularly accessible. Most garage conversions result in studios or one-bedroom units ranging from 400 to 600 square feet.
- Typical Size: 400-600 sq ft
- Timeline: 3-5 months typical
- Cost: 30-50% less than new construction
- Best For: Budget-conscious, quick timeline
Junior ADU (JADU)
A smaller unit of up to 500 square feet created within your existing home's footprint, typically by converting a bedroom, basement, or attached garage. JADUs must include a cooking facility (at minimum, a sink, counter, and small appliance outlet) but can share a bathroom with the main house. In Brentwood, you can build both a JADU and a full ADU on the same property, maximizing your housing options. JADUs require owner-occupancy in either the main house or the JADU itself.
- Max Size: 500 sq ft
- Location: Within existing home
- Requirements: Owner-occupancy required
- Best For: Minimal construction, family use
Above-Garage ADU
Build a new living unit above your existing or new garage structure. This two-story approach preserves your parking while adding living space above. In Brentwood, above-garage ADUs can reach 18-20 feet in height depending on distance from property lines. This option is particularly popular in neighborhoods with narrow lots where backyard space is limited. The elevated position often provides better views and natural light than ground-level units.
- Max Size: Up to 1,200 sq ft
- Height: Up to 18-20 feet
- Parking: Preserved below unit
- Best For: Limited lot space, maintaining parking
Basement Conversion
While less common in Southern California due to construction patterns, properties with existing basements can convert that space into an ADU. Basement conversions require proper egress windows, adequate ceiling height (at least 7 feet in habitable areas), and may need waterproofing and ventilation upgrades. When properly executed, basement ADUs provide naturally cool living space and complete separation from the main home's daily activities.
- Max Size: Existing footprint
- Requirements: Egress, ceiling height
- Benefits: Cool temps, full separation
- Best For: Existing basements only
Complete ADU Services in Brentwood
From initial feasibility analysis through final inspection, we handle every aspect of your ADU project. Our Brentwood-focused approach ensures your project meets all local requirements while maximizing value.
Feasibility Analysis
We begin every project with a comprehensive analysis of your property's ADU potential. Our team reviews your lot size, zoning, setbacks, utility connections, and neighborhood context to determine what you can build. In Brentwood, this includes understanding any overlay zones, historic district requirements, or other local factors that might affect your project. You receive a detailed report showing your options, estimated costs, and potential rental income before committing to design work.
- Property zoning verification
- Setback and lot coverage analysis
- Utility capacity assessment
- Cost and ROI projections
Design & Architecture
Our design team creates ADU plans tailored to your property and goals. Whether you want a modern studio for maximum rental income or a two-bedroom unit for family members, we design spaces that work. We understand Brentwood architectural context and create designs that complement existing homes while meeting all building code requirements. Every design includes structural engineering, Title 24 energy compliance, and all documentation needed for permits.
- Custom floor plan development
- 3D renderings and visualizations
- Structural engineering
- Energy compliance documentation
Permitting & Approvals
Navigating Brentwood permitting can be complex, but we handle it all. Our team prepares complete permit applications, manages plan check submissions, and coordinates with building department staff to address any comments or corrections. We track your application through the approval process and keep you informed of progress. Our experience with Brentwood regulations helps avoid common pitfalls that delay other projects.
- Complete permit application prep
- Plan check management
- Building department coordination
- Permit tracking and updates
Construction
Our licensed construction team builds your ADU with quality materials and skilled craftsmanship. We handle all aspects of construction including foundation, framing, electrical, plumbing, HVAC, insulation, drywall, flooring, cabinets, and finishes. Throughout the build, we coordinate required inspections, manage subcontractors, and keep you updated on progress. Our goal is delivering a finished ADU that exceeds your expectations while respecting your timeline and budget.
- Licensed general contractor
- Quality materials and finishes
- Inspection coordination
- Project management and updates
Interior Design
A well-designed interior maximizes both livability and rental appeal. Our interior design services help you select finishes, fixtures, and colors that create appealing spaces within your budget. We offer curated finish packages at different price points, or work with you to customize selections. From kitchen layouts that maximize counter space to bathroom designs that feel spacious, we sweat the details that make small homes work beautifully.
- Finish and fixture selection
- Space planning optimization
- Curated design packages
- Custom interior options
Financing Guidance
We help connect you with financing options suited to your situation. Many Brentwood homeowners use home equity, construction loans, or specialized ADU financing products to fund their projects. We can introduce you to lenders experienced in ADU financing and help you understand options including cash-out refinancing, HELOCs, and construction-to-permanent loans. While we're not lenders ourselves, our guidance helps you navigate financing decisions confidently.
- Financing option overview
- Lender introductions
- ROI and cash flow projections
- Budget planning assistance
How We Build Your Brentwood ADU
Our streamlined process takes you from initial concept to move-in ready ADU. Here's what to expect at each stage of your project.
Free Consultation
We start with a free consultation to understand your goals, assess your property, and explain your options. This can happen via phone, video call, or an in-person site visit in Brentwood. You'll learn what you can build, approximate costs, and timeline expectations.
Feasibility Study
Our team conducts a thorough analysis of your Brentwood property. We verify zoning, calculate setbacks and lot coverage, assess utility connections, and identify any site-specific considerations. You receive a written report with your ADU options.
Design Development
Working with our architects and designers, you'll develop floor plans, select exterior styles, and make finish selections. We create 3D renderings so you can visualize the finished ADU before construction begins.
Permitting
We submit your complete permit application to Brentwood and manage the entire approval process. This includes responding to plan check comments and coordinating with building department staff through to permit issuance.
Construction
With permits in hand, construction begins. Our crews work efficiently while respecting your property and neighbors. For a typical Brentwood ADU, construction takes 4-6 months. You'll have a dedicated project manager throughout the build.
Walkthrough & Move-In
We conduct a detailed walkthrough, demonstrate systems and appliances, and address any punch list items. Once final inspections are complete, you receive your certificate of occupancy. Your new Brentwood ADU is ready.
ADU Costs in Brentwood
Understanding ADU costs helps you plan realistically and evaluate the investment opportunity. Here's what to expect for typical Brentwood ADU projects.
Garage Conversion
$100,000 - $180,000Converting an existing garage is typically the most affordable path to an ADU. You save on foundation and framing since the basic structure exists. Costs vary based on garage condition, size, and finish level desired. Most garage conversions in Brentwood result in studios or one-bedroom units between 400-600 square feet.
- Electrical and plumbing installation
- HVAC system
- Insulation and drywall
- Kitchen and bathroom
- Flooring and finishes
- Permits and inspections
Detached New Construction
$200,000 - $400,000Building a new detached ADU involves complete construction from the ground up. This option costs more but offers maximum design flexibility and typically commands higher rents. A one-bedroom detached ADU in Brentwood typically costs $200,000-$280,000. Two-bedroom units range from $280,000-$400,000 depending on size and finishes.
- Foundation and site work
- Complete framing and roofing
- All mechanical systems
- Interior and exterior finishes
- Utility connections
- Design, engineering, permits
Attached Addition
$150,000 - $300,000Attached ADUs share a wall with your existing home, which can reduce some construction costs. You may be able to tie into existing roof structure and foundation, though this depends on your home's configuration. Costs fall between garage conversions and fully detached new construction for most Brentwood projects.
- Foundation extension (if needed)
- Framing and roofing integration
- Separate entrance and utilities
- Complete interior buildout
- Fire separation requirements
- Permits and inspections
Return on Investment
Actual rents depend on unit size, finishes, location within Brentwood, and current market conditions. One-bedroom ADUs typically rent higher than studios; two-bedroom units command premium rates.
According to Freddie Mac research, ADUs add 20-30% to property values in high-demand California markets. This often exceeds construction costs, creating immediate equity.
When you factor rental income against construction costs, many Brentwood ADUs generate 8-12% annual cash-on-cash returns, competitive with or exceeding other investment options.
Frequently Asked Questions About ADUs in Brentwood
Get answers to the most common questions about building an accessory dwelling unit in Brentwood.
Read Our Blog
Expert insights, tips, and guides to help you plan your ADU project.
How to Build an ADU That Passes Inspection the First Time
Expert guide to passing ADU inspections on the first attempt. Covers common inspection failure points, preparation check...
Read More
ADU Roofing Options: Materials, Costs, and Lifespan Compared
Compare ADU roofing materials including asphalt shingles, metal roofing, concrete tile, and flat roof options. Covers co...
Read More
How to Plan Outdoor Living Spaces Between Your ADU and ...
Design guide for creating functional outdoor living spaces between your ADU and main home. Covers patio designs, dining ...
Read MoreReady to Build Your ADU in Brentwood?
Get expert guidance on permits, design, and construction. Our team knows Brentwood regulations inside and out.