Do I Need an Architect for My ADU in California?

One of the most common questions when starting an ADU project is whether you need to hire an architect. The answer depends on your project type, design goals, and chosen approach. While architects aren’t legally required for all ADUs in California, understanding when you do and don’t need one can save you time and money while ensuring a successful project.

Quick Answer

Scenario	Architect Required?	Alternative Options
Using Pre-Approved Standard Plans	NO	Plans already designed and approved
Design-Build Contractor with In-House Design	NO	Designer or drafts person can prepare plans
Simple Custom ADU (under 2 stories)	NO (but recommended)	Building designer or draftsperson
Complex Custom Design	YES (highly recommended)	Licensed architect ensures quality
Historic District (HPOZ)	YES (practically required)	Architect experienced with HPOZ review
Hillside or Complex Site	YES (recommended)	Architect + structural engineer team
Two-Story ADU	NO (but beneficial)	Designer can do it; architect adds value
Luxury/High-End ADU	YES (recommended)	Architect ensures design quality

California Law: What’s Actually Required

Legal Requirements for ADU Plans

California Building Code and Los Angeles requirements state that plans must be prepared by:

Licensed Architect, OR
Licensed Building Designer, OR
Professional Engineer, OR
Certified Draftsperson (for simpler projects)

Key Point: You do NOT legally need a licensed architect for most residential ADU projects in California. However, structural engineering is required regardless of who designs the project.

When an Architect License IS Required by Law

Per California Business and Professions Code Section 5537, you MUST use a licensed architect for:

Buildings over 2 stories
Commercial structures
Projects over certain size/complexity thresholds
Multiple dwelling buildings (apartment complexes)

Most single-family ADUs don’t trigger these requirements.

Your Four Main Options for ADU Design

Option 1: Pre-Approved Standard Plans

Cost: $0 – $2,000 (plans only)

Timeline: Immediate to 2 weeks for site adaptation

Pros:

Lowest cost option
Fastest permitting (plans pre-approved by LADBS)
Proven designs that work
Minimal design fees
Reduced risk of plan check corrections

Cons:

Limited customization
Standard layouts may not optimize your lot
Less unique design
May not fit your specific aesthetic goals

Best for:

Budget-conscious projects
Fast-track timelines
Standard rectangular lots
Rental income focus (function over form)

Option 2: Building Designer / Draftsperson

Cost: $5,000 – $15,000

Timeline: 6-10 weeks

Pros:

Custom design at moderate cost
Experienced with residential code requirements
Focus on buildability and functionality
Often work closely with contractors
Good understanding of LA permit process

Cons:

Limited architectural vision/creativity
May not push design boundaries
Varies widely in skill level
Less suited for complex sites

Best for:

Straightforward custom designs
Practical, functional focus
Budget to mid-range projects
Standard lot configurations

Option 3: Architect (Licensed)

Cost: $12,000 – $35,000+

Timeline: 8-14 weeks

Pros:

Professional design expertise
Creative problem-solving for difficult sites
Higher aesthetic quality
Holistic approach to space, light, materials
Project management and construction oversight available
Better integration with main house architecture

Cons:

Higher cost (typically 10-15% of construction budget)
Longer design timeline
May design features that increase construction costs
Could be overkill for simple projects

Best for:

Complex or constrained sites
High-end projects
Unique design vision
Historic districts (HPOZ)
Hillside properties
When aesthetics are top priority

Option 4: Design-Build Contractor

Cost: $8,000 – $20,000 (included in project)

Timeline: 6-10 weeks

Pros:

Single point of contact for design and construction
Design focused on buildability and cost-efficiency
Integrated process reduces miscommunication
Often includes in-house designer or architect
Streamlined workflow

Cons:

Limited design options (what contractor offers)
Potential conflict of interest (designer works for builder)
May push toward contractor’s preferred methods
Less independent design advocacy

Best for:

Homeowners who want simplicity
Moderate customization needs
Trust-based contractor relationships
Value efficiency over unique design

Cost Comparison: Design Approaches

Design Approach	Design Fees	Total 800 sq ft ADU Project Cost	Design as % of Total
Pre-Approved Plans	$500 – $2,000	$165,000	0.3-1.2%
Building Designer	$8,000 – $15,000	$185,000	4.3-8.1%
Design-Build	$10,000 – $18,000 (bundled)	$195,000	5-9% (bundled)
Architect	$18,000 – $35,000	$225,000	8-15.5%
High-End Architect	$35,000 – $60,000	$300,000+	12-20%

What Architects Actually Do for ADU Projects

Full Architectural Services Include:

1. Pre-Design / Programming (Week 1-2)

Site analysis
Code research (zoning, setbacks, FAR)
Client needs assessment
Budget discussions
Feasibility studies
Preliminary concepts

2. Schematic Design (Week 3-5)

Develop 2-3 design options
Floor plans and elevations
Site planning and orientation
Material concepts
Preliminary cost estimates
Client presentations and revisions

3. Design Development (Week 6-9)

Refined floor plans with dimensions
Interior and exterior elevations
Building sections
Material and finish selections
Kitchen and bathroom layouts
3D renderings or models
Coordination with structural engineer

4. Construction Documents (Week 10-14)

Detailed architectural plans
Building code compliance documentation
Door and window schedules
Finish schedules
Details and specifications
Coordinate with engineers (structural, MEP)
Energy code compliance (Title 24)

5. Permit Phase (Week 15-25+)

Submit plans to building department
Respond to plan check corrections
Revise drawings as needed
Coordinate with other consultants
Attend permit meetings if required

6. Construction Administration (Optional, During Construction)

Respond to contractor questions
Review submittals and shop drawings
Site visits to verify design intent
Process change orders
Review construction quality
Final punch list review

Typical Architectural Fee Structures

Fee Type	Typical Rate	Best For
Percentage of Construction Cost	10-15% of build cost	Full service projects, aligns incentives
Fixed Fee	$15,000 – $40,000	Well-defined scope, predictable costs
Hourly Rate	$150 – $300/hour	Consultations, small scopes, revisions
Per Square Foot	$15 – $40/sq ft	Simple comparison, easy budgeting

When You Should Definitely Use an Architect

Scenario 1: Historic Districts (HPOZ)

If your property is in a Historic Preservation Overlay Zone:

Design review is required before permitting
ADU must be compatible with historic character
Strict guidelines on materials, style, massing
HPOZ Board review process is complex
Architects experienced in HPOZ are essential

HPOZ neighborhoods include:West Adams, Angelino Heights, Carthay Circle, Windsor Square, Hancock Park, and 30+ others in LA

Scenario 2: Hillside or Steep Slope Properties

Foundation design is complex
Drainage and grading critical
Structural challenges with slopes
Potential soil stability issues
View preservation considerations
Architect + structural engineer team needed

Scenario 3: Challenging Lot Configurations

Narrow lots
Irregularly shaped properties
Heavy easement constraints
Significant setback challenges
Limited building envelope
Architect’s spatial problem-solving is valuable

Scenario 4: High-End / Luxury Projects

Budget over $350,000
Premium finishes and materials
Unique design vision
Resale value maximization
Architectural statement piece
Architect ensures design quality matches investment

Scenario 5: Integration with Architecturally Significant Main House

Mid-century modern homes
Craftsman bungalows
Spanish Revival estates
Other distinctive architectural styles
Architect can honor and complement existing design

When You Can Skip the Architect

Good Candidates for Designer or Pre-Approved Plans:

Flat, rectangular lots– No unusual challenges
Rental income focus– Function over form priority
Budget constraints– Need to minimize soft costs
Fast timeline– Pre-approved plans accelerate permitting
Standard design preferences– Don’t need unique design
Experienced design-build contractor– Trusted team with in-house capability

Engineering Requirements (Separate from Architecture)

Structural Engineering: ALWAYS Required

Regardless of who designs your ADU, you MUST have structural engineering:

Required by code for all new structures
Foundation design and calculations
Framing design (beams, headers, connections)
Seismic and wind load analysis
Roof structure design

Cost: $3,000 – $8,000 typically

Other Engineering (As Needed)

Engineering Type	When Required	Typical Cost
Civil Engineering	Grading, drainage, complex sites	$2,000 – $6,000
Geotechnical	Hillside, poor soils, seismic zones	$3,000 – $8,000
MEP (Mechanical/Electrical/Plumbing)	Complex systems, some jurisdictions	$2,000 – $5,000
Title 24 Energy Compliance	All projects (sometimes done by architect/designer)	$800 – $2,000

Questions to Ask When Hiring an Architect

Essential Questions:

“How many ADUs have you designed in Los Angeles?”
- Look for: 10+ ADU projects
- LA-specific experience is valuable
“Are you familiar with current ADU state laws and LA requirements?”
- Laws changed significantly 2020-2025
- Outdated knowledge causes permit delays
“What’s your fee structure and what does it include?”
- Get clear scope of services
- Understand what costs extra
- Ask about construction administration
“How do you handle permit corrections and revisions?”
- Are revisions included or extra?
- How many review cycles are expected?
“Do you coordinate with structural and other engineers?”
- Should be part of service
- Ensures integrated documents
“Can you provide references from recent ADU clients?”
- Contact past clients about experience
- Ask about timeline, budget, issues
“What’s your typical timeline from contract to permit-ready plans?”
- Realistic expectations matter
- 8-14 weeks is typical for custom
“Do you offer construction administration services?”
- Site visits during construction
- Verify design intent
- Costs extra but valuable

The Design-Build Approach: Alternative to Separate Architect

How Design-Build Works

Design-build contractors offer a single contract for both design and construction:

Process:

Initial consultation and needs assessment
In-house designer/architect develops plans
Design and pricing developed together
Seamless transition from design to construction
One point of contact throughout

Advantages:

Simplified communication and accountability
Design informed by buildability and cost
Faster overall timeline
Fewer change orders (builder involved from start)
Single contract, single warranty

Disadvantages:

Designer works for builder (potential conflict)
May not get most creative design
Limited to contractor’s design capabilities
Less independent advocacy for owner

As a design-build ADU contractor in Los Angeles, we offer in-house design services that balance cost, timeline, and quality for most ADU projects.

Hybrid Approach: Architect for Design, Contractor for Engineering

Some homeowners hire an architect for schematic design only:

Process:

Architect develops design concept and preliminary plans (4-6 weeks)
Contractor’s team completes construction documents
Contractor coordinates engineering
Architect available for consultation (hourly)

Cost savings: 30-50% vs full architectural service

Benefits: Professional design vision with practical execution

DIY Design: Can You Design Your Own ADU?

Short Answer: Legally Yes, Practically Difficult

You CAN design your own ADU plans, BUT:

Still need licensed engineer to stamp structural
Must meet all building codes (complex)
Energy compliance (Title 24) is technical
Plan check corrections likely
May not save money due to delays and revisions
Lenders may not finance owner-designed plans

Realistic DIY approach:

Start with pre-approved plans
Make minor modifications
Hire designer to finalize for permits
Engineering still required

Not recommended unless you have construction/design background.

Making the Decision: Decision Tree

Start here: What’s your primary goal?

If Goal = Maximum Rental Income at Lowest Cost

→Use pre-approved plans ($500-$2,000)

→ Fastest permits, lowest design costs, proven functional layouts

If Goal = Custom Design on a Budget

→Hire building designer ($8,000-$15,000)

→ OR usedesign-build contractor ($10,000-$18,000 bundled)

If Goal = Unique, High-Quality Design

→Hire licensed architect($18,000-$35,000+)

If Property is Hillside, HPOZ, or Very Complex

→Hire experienced architect (non-negotiable)

If You Want Simplicity and One Point of Contact

→Design-build contractor with in-house design

Cost-Benefit Analysis Example

Scenario: 800 sq ft detached ADU on flat lot

Option A: Pre-Approved Plans

Design cost: $1,500
Construction cost: $165,000
Total: $166,500
Timeline: 7-9 months
Result: Functional, standard design

Option B: Building Designer

Design cost: $12,000
Construction cost: $180,000 (some customization adds cost)
Total: $192,000
Timeline: 9-11 months
Result: Custom layout, standard aesthetics

Option C: Architect

Design cost: $25,000
Construction cost: $210,000 (architect designs may cost more to build)
Total: $235,000
Timeline: 10-13 months
Result: High-quality design, unique aesthetic, maximizes site potential

Value Analysis:

Option A property value increase: +$220,000
Option B property value increase: +$260,000
Option C property value increase: +$320,000

ROI Comparison:

Option A: 132% ROI
Option B: 135% ROI
Option C: 136% ROI

High-quality architecture can add more value in high-end neighborhoods

Get Professional Guidance

The decision about whether to hire an architect depends on your specific project, goals, budget, and site conditions. There’s no one-size-fits-all answer.

As Los Angeles ADU contractors and code compliance specialists, we can help you determine the best design approach for your project:

Assess whether your site needs architectural expertise
Connect you with experienced ADU architects and designers
Provide design-build services with in-house design
Navigate permitting regardless of design approach
Ensure code compliance and resolve existing violations

Start with our ADU Eligibility Check and Cost Calculator to understand your project scope, then we can discuss the right design approach for your needs.

Bottom line: For most standard ADU projects on typical lots, a building designer or design-build contractor is sufficient. For complex sites, historic districts, or high-end projects, invest in a licensed architect.

ADU Eligibility Check

ADU Cost Calculator