Thousand Oaks ADU Builders, Permit Requirements, and Plans

Imagine this: Your aging parents move into a beautiful, self-contained cottage right behind your main house. Your garage, once packed with boxes and old tools, is now a modern studio rented by a local teacher or nurse. These are not just dreams. In Thousand Oaks, California, these scenarios are becoming everyday realities, thanks to progressive housing policies and the recent passage of Ordinance 1732-NS, which updates the city’s rules on Accessory Dwelling Units (ADUs) and Junior Accessory Dwelling Units (JADUs).

ADUs and JADUs are transforming how homeowners approach their property—and helping cities like Thousand Oaks respond to California’s growing housing challenges. With thoughtful planning, clear rules, and support from the city, homeowners can now create beautiful, functional, and income-generating spaces that benefit both their families and their neighborhoods.

In this blog post, we’ll cover everything you need to know about ADUs and JADUs in Thousand Oaks—from what’s allowed and where to build, to real-life stories and financial tips. Let’s dive in.

The Big Picture: Why ADUs and JADUs Matter

The California Housing Crisis

California has long faced a severe housing shortage. Rapid population growth, combined with zoning restrictions and limited new development, has led to soaring home prices and rental costs. Families are being priced out of the communities they grew up in. Seniors are struggling to downsize. Essential workers can’t afford to live where they work.

ADUs and JADUs offer a practical and powerful solution. By adding small, self-contained units to existing residential lots, cities can increase housing supply without changing neighborhood character.

What Are ADUs and JADUs?

• ADUs (Accessory Dwelling Units): Also called “granny flats” or “backyard homes,” these are independent living units with a kitchen, bathroom, and sleeping area. They can be attached to the main house, converted from a garage, or completely detached in the backyard.
• JADUs (Junior Accessory Dwelling Units): These are smaller (max 500 sq ft) and must be within the walls of the existing home. They need a separate entrance and an efficiency kitchen but may share a bathroom with the main residence.

How Thousand Oaks is Leading the Way

On November 22, 2024, the City of Thousand Oaks enacted Ordinance 1732-NS, aligning local ADU rules with California’s broader state laws. The ordinance reflects a growing recognition that well-designed ADUs can help cities balance growth, sustainability, and community character.

Highlights of the ordinance include:

• Simplified permit process
• Clear size and design rules
• Parking flexibility
• Allowances for both single-family and multi-family properties

Let’s explore the most important elements.

Getting Started: The Permit Process

Where to Begin

The process starts at the Thousand Oaks Community Development Department. Homeowners must submit two main applications:

1. ADU/JADU Permit Application
2. Building Permit Application

The review process is ministerial—this means that if your project complies with all applicable standards, the city must approve it. There are no public hearings or discretionary reviews involved.

Processing Time

Applications are reviewed and processed within 60 days. If your plan doesn’t meet a requirement, the city will notify you promptly and explain what needs to be corrected. This streamlined process removes delays and uncertainty that used to discourage many homeowners from pursuing ADUs.

Where and What Can You Build?

Thousand Oaks’ ordinance allows ADUs and JADUs in both single-family and multi-family residential zones.

Single-Family Zones (e.g., R-1, R-E)

You can build:

• One ADU (attached, detached, or garage conversion)
• One JADU (within the existing home)

💡 Example: A family living in a 3-bedroom R-1 home can convert part of their house into a JADU for their college-aged child and build a detached ADU in the backyard to generate rental income.

Multi-Family Zones (e.g., R-2, R-3, MU)

You can:

• Convert non-livable space (e.g., basements, storage rooms) into ADUs, up to 25% of the existing units
• Build up to 2 detached ADUs on the lot

Restrictions apply in certain cases:

• No ADUs on lots with slopes over 25%
• Not allowed in areas with wildfire risk
• Prohibited where deed restrictions prevent additional structures

Design Rules: Size, Style, and Requirements

Thousand Oaks has adopted ADU standards that balance flexibility with neighborhood aesthetics.

JADUs

• Max size: 500 sq ft
• Must be within the main house
• Must have an efficiency kitchen
• May share a bathroom with the main home
• Requires a separate entrance

Attached ADUs

• Max size: 850 sq ft or 50% of main house size, whichever is greater
• Must have a full kitchen and bathroom
• Setbacks: 4 feet side/rear
• Max height: 25 feet

Detached ADUs

• Max size:
  • 850 sq ft for studios/1-bed
  • 1,200 sq ft for 2-bedroom units (on 1-acre lots or more)
• Max height:
  • 16 feet normally
  • 18 feet if near transit or to match primary home’s roof pitch
• Setbacks: 4 feet rear/side

Design Consistency

• Attached ADUs must match the main home in at least one way (materials, roof slope, or colors)
• Detached ADUs need at least one matching design feature
• Privacy rules: Frosted glass required for windows facing neighbors
• No rooftop decks or external stairs for second-story ADUs

Parking, Utilities, and Fire Safety

Parking

• Most ADUs require 1 off-street space
• Can be in tandem, driveway, or setback
• Exempt from parking if:
  • Within 0.5 miles of public transit
  • Located in historic districts
  • Created from existing structures (e.g., garage conversions)

Garage conversions do not require replacing the lost parking.

Utilities

• New ADUs require separate utility connections
• Conversions may share existing lines
• Fire sprinklers required only if the main home also needs them
• On septic systems: You must prove the system can handle the added load before construction

Special Considerations: Trees and Ridgelines

Thousand Oaks values its natural beauty, especially its namesake oak trees and scenic ridgelines. The city’s ordinance includes protections to preserve this character:

• No ADUs in protected tree zones or along scenic ridgelines, unless:
  • It’s the only way to build an 800 sq ft ADU
  • You agree to replant removed trees or pay mitigation fees

This keeps the city green and ensures development doesn't disrupt the visual landscape.

The Cost Factor: Building and Saving

Typical Construction Costs

ADU costs vary depending on size, location, and features. On average:

• Garage Conversion ADU: $100K – $150K
• Detached ADU: $150K – $300K+
• JADU (Interior Conversion): $40K – $80K

Materials, labor, permitting, and site conditions all affect final price.

Incentives & Savings

Thousand Oaks helps ease financial pressure with:

• Impact fee exemption for ADUs under 750 sq ft
• Utility fee waivers if not tied to a new primary residence

Over time, rental income can make a big difference. A detached ADU could earn $2,000–$3,000/month, offsetting mortgage payments or property taxes.

Statewide Exemptions That Help

California law provides extra protections and exemptions for homeowners:

Under Gov. Code Section 65852.2, you’re eligible for ministerial approval when:

• Converting part of your house or garage into an ADU or JADU (+150 sq ft for access)
• Building one detached 800 sq ft ADU on a single-family lot
• Creating up to two detached ADUs on multi-family lots
• Converting non-livable space (e.g., basement) into ADUs—up to 25% of existing units

These projects bypass many local development restrictions and help you build faster.

Real Stories from Thousand Oaks Residents

Sarah’s Garage Conversion

Sarah converted her garage into a 500 sq ft ADU for her elderly mother.
“It gave Mom independence, and I know she’s safe and close by. Plus, the conversion increased our property value.”

John’s Backyard Cottage

John, a retiree, built a detached ADU for his daughter’s family.
“They were struggling with rent. Now they’re saving for a home while we get quality time with our grandkids.”

Lisa the Nurse

Lisa, a healthcare worker, rents her JADU to a fellow nurse.
“The rental income covers my property tax. And it helps another essential worker stay in town.”

These stories show how ADUs strengthen families and support community stability.

Common Challenges (and How to Overcome Them)

ADUs bring plenty of benefits, but they’re not without issues:

1. High Construction Costs

Solution: Start with a JADU or garage conversion. Apply for grants, city incentives, or partner with a financing company.

2. Permitting Confusion

Solution: Work with a local expert or permitting service to avoid costly mistakes and delays.

3. Neighbor Concerns

Solution: Follow design rules strictly—especially setbacks, privacy glass, and height limits—to keep peace in the neighborhood.

Looking Ahead: The Future of Housing in Thousand Oaks

Thousand Oaks isn’t just embracing ADUs—it’s leading the way. By enacting Ordinance 1732-NS, the city is promoting:

• Affordable housing
• Smarter land use
• Family-friendly solutions
• Sustainable, low-impact development

Whether you’re a homeowner with underused space, a renter looking for a stable home, or a builder exploring new projects, the Thousand Oaks ADU ordinance opens exciting new doors.

Ready to Start?

Here’s how to take the first step:

✅ Visit the Thousand Oaks Community Development Department
✅ Read Ordinance 1732-NS in full
✅ Talk to a designer, architect, or contractor who specializes in ADUs
✅ Explore financing options or grants
✅ Plan your unit and submit your permit application

The housing revolution is happening—right in your backyard. Don’t miss your chance to build a better future for your family, your finances, and your city.