When we started designing our modular home in California, we were told something that sounded incredibly promising: “You can build anything you want.”
Our property sits in a planned development zoning district, which is intended to give cities flexibility in determining how the land is used for new builds.
What we didn’t realize was that planning department approval in California – even for traditional site-built homes – isn’t just about meeting California’s regulatory requirements or local building department requirements. It’s about interpretation, process, and a series of requirements that often don’t surface until you’re deep into the design.
Understanding how to navigate the Planning Department process to achieve modular home approval in California before a building permit is ever issued is critical – and in our case, it shaped nearly every aspect of the final design to comply with state and local building requirements.
Not All Planning Departments Are the Same
Before applying for building permits, your project must be approved by the city Planning Department. Homeowners building a modular or manufactured home will find that working with the local planning and building departments can range from relatively straightforward to far more challenging.
We knew that building on a downtown urban infill lot in California would come with additional constraints compared to a suburban property. But when we were warned that our city’s Planning Department had a reputation for being one of the most difficult in the county, we quickly learned that was not an exaggeration.
Takeaway: The local Planning Department review and approval process can vary significantly depending on the city – even within the same county.
“You Can Build Anything”… Within Limits
Once you submit your drawings, you’re assigned a project planner. In our case, the city uses a fairly streamlined process where the planner routes your plans through multiple city or county departments – Public Works, Fire, Building, and others – for plan review to make sure the project meets all requirements. This is where you really start to see how California and local codes and standards apply to your project – and how those decisions can ultimately impact construction.
Next comes the Site and Architectural Review Committee (SARC), which focuses on aesthetics set by the city guidelines. Because our lot was located in a historic district, design became a major factor.
SARC asked us to provide alternative exterior color options, reduce the perceived size of the home, make the porch more decorative, and replace the concrete driveway with pervious pavers.
Cities also regulate something called Floor Area Ratio (FAR), which is the maximum allowable floor area relative to lot size. FAR is a critical factor that homeowners must consider when designing their home. In our case, we were allowed 65%, but the garage had to be included in that calculation- even though it’s not livable space. This requirement ultimately forced us to modify our floor plan to stay within the allowed limits.
Requirements That Changed Mid-Process
One of the most challenging aspects of getting a California building permit for a modular home was how requirements evolved – sometimes introducing additional risk. In our case, when the Planning Department required us to incorporate cantilevered sections, it meant our builder had to be able to accommodate that design – otherwise, we would have needed to find one who could.
This wasn’t an isolated issue – we saw similar changes across multiple aspects of the project:
A basement kitchen was initially restricted to a wet bar
→ Later required to be an “efficiency kitchen” under California SB-330
An exterior side entry was initially denied
→ Later required under California state law
Parking requirements initially required more than two spaces
→ Later reduced to one under California AB-2097
Rooftop decks were not allowed under local interpretation
→ A rooftop deck over the garage was later suggested
Gas lines were prohibited, reconsidered, then prohibited again
→ We ultimately chose an all-electric home
A more decorative porch was required by SARC
→ Later the Planning Department preferred no decoration
Lesson: Don’t get too attached to your plans – especially in California. They will change.
Navigating Modular Home Approval in California (What to Expect)
Understanding the planning approval process in California is critical, because it’s where your project can change significantly before you ever reach the permit stage. In most cases, planning approval must be completed before you can even submit for a building permit. From there, the project moves into the permits and inspection phase, with site inspections taking place throughout construction.
SARC (Site & Architectural Review Committee)
- Focuses on aesthetics and neighborhood compatibility
- Provides guidance, but not final approval
Planning Commission
- Final decision-makers for your project
- Can override prior reviews
What surprised us most at the Planning Commission Meetings:
- You present first – then you can’t participate further
- Questions raised by the board or public become future action items because you can’t participate
- It can take 2+ months to get back on the agenda
- Meetings can be canceled with little notice
- Decisions typically follow Planning Department recommendations
- A denial may result in additional fees to revise and respond to comments
Takeaway: Even when working closely with a project planner, planning development recommendations and planning commission outcomes can feel unpredictable. That said, be prepared for requirements to change.
Planning Timelines: Expect the Unexpected
One thing we didn’t fully appreciate at the beginning was how much the permitting process and planning timelines can vary when working with different cities.
In some cases, planning approval can move relatively quickly – sometimes within a few months. In others, like ours, the process can take years.
While builders often provide estimated timelines, much of what happens during city review is outside their control. Review cycles, responsiveness, and scheduling can significantly impact how long things actually take – and those delays can directly affect construction costs.
Takeaway: Treat timelines as estimates, not guarantees – and plan for the submittal process to take longer than expected.
California-Specific Building Challenges
Building a modular home in California comes with additional requirements that can significantly impact your design, including compliance with local residential construction building department codes.
Because our project began in 2017, many newer requirements were introduced after our modular plans were already approved by a state level third-party DAA (Design Approval Agency).
- No Gas in New Construction
Local policies shifted multiple times. Rather than continue revising plans, we moved forward with an all-electric home – a sustainable option many modular home builders offer. - Hybrid Water Heater Requirements
Hybrid water heater systems require significant air volume (clearance requirements), which didn’t fit our original layout. This forced us to select a more expensive exterior heat pump system. - Title 24 Energy Code (Energy Efficiency) Requirements
Electric tankless water heaters were not allowed, and whole-house ventilation systems are now required under California’s energy code to comply with state standards. - Solar and Electrical Vehicle Requirements
Our project already included solar panels and EV infrastructure, so this had minimal impact.
Takeaway: Local agencies and state building codes change frequently. Each modification can trigger updates to multiple reports (such as Title 24 energy calculations and structural plans) and may require new approvals.
Modular Construction Adds Another Layer
One of the biggest challenges we encountered was the disconnect between modular construction rules and local planning departments.
In California, besides complying with the California Department of Housing and Community Development (HCD) codes:
- Planning Departments have authority over:
- zoning
- exterior design
- on-site work
- The factory-built structure:
- is reviewed by a third-party DAA
- is not supposed to be re-reviewed by the city
However, not all cities are familiar with this process.
Key lessons:
- Ensure your modular plans are DAA-approved
- Confirm the city understands modular jurisdiction limits
- Be aware that some cities may attempt to review or charge fees for factory-approved structures
- Early planning matters, especially when customization is involved – for us, the city didn’t accept the common rectangular modular design, which meant redesigning the home with cantilevered sections
A Costly Lesson: Submitting Unstamped Modular Plans
One of the most expensive and time-consuming mistakes that was made had nothing to do with design – it had to do with when and how our modular plans were submitted to the local building authority.
Although the builder had already created DAA-stamped modular plans, they were not submitted to the city. Instead, our project manager submitted working copies of the drawings that had been used to incorporate city comments.
At the time, we didn’t realize that DAA-stamped portions of modular plans are not subject to local jurisdiction review.
Because of this, we paid for a full city review on drawings that were not submitted in their DAA-approved form.
The result?
- The city reviewed portions of the home they technically didn’t need to
- We were required to make multiple changes to the design
- The city added extensive annotations and comments that likely would not have applied to the stamped modular plans
By the time we better understood how DAA-stamped plans should be handled by the city, we had already paid multiple fees.
We asked the city if any portion of the review fees could be refunded, but the answer was no – the work had already been completed.
Looking back, submitting stamped plans from the beginning would have significantly reduced the number of required modifications and review fees.
Another important factor we didn’t fully understand at the time is how state laws like SB-330 can influence costs in California – especially when it comes to how different agencies interpret fees for on-site work and infrastructure. We’ll break this down in a future post.
Why Timing Matters in Modular Construction
This issue becomes even more critical when you consider how changes ripple through a modular project.
If the city requires a modification that affects:
- the structure
- mechanical systems (such as whole-house ventilation or energy recovery)
- or any Title 24-related components
you may be required to go back through DAA approval again for updated plans.
That doesn’t just mean revising one drawing.
It can trigger updates to:
- modular construction drawings
- Title 24 energy calculations
- site plans
- grading plans
- and other supporting documents
Each of these updates often comes with:
- additional consultant fees
- new review cycles
- and extended timelines
And timing is rarely simple.
Many of these documents are interdependent, meaning:
- one revision cannot be completed until another is finalized
- updates must be done in sequence, not all at once
To make matters more challenging, review timelines can take a month or more, unless you pay additional fees to expedite your project.
Takeaway: For modular construction, getting the approval sequence right from the beginning is critical.
Submitting unstamped drawings can lead to:
- unnecessary design changes
- duplicated review efforts
- higher costs
- and significant delays
Understanding how DAA approval, city review, and supporting documents interact can save both time and money – and help avoid rework that could have been prevented.
What We Learned About Getting a Modular Home Approved in California
- Planning guidance can be inconsistent
- Zoning interpretations can change mid-project
- State laws like SB-330 can override local requirements
- Delays are part of the process
- Understanding modular approval rules can save time and money
Final Thoughts
Getting planning department approval isn’t a single step – it’s an ongoing process of interpretation, adjustment, and coordination. Even as our plans worked their way through the modular home approval process in California, we began to see how different departments interpreted the same requirements in different ways.
For us, navigating the modular home permitting process, zoning restrictions, and evolving California building requirements was just the beginning. We’ll cover the challenges of the building permit process in a future post.
If you’re planning a residential modular home project in California, it’s worth reviewing the California HCD codes to understand what the city can regulate – and what falls under state approval.
Excavation, shoring, and building on a tight urban infill lot introduced an entirely new set of challenges – which we’ll cover in a future post.
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