As the demand for housing increases and property owners look for smart ways to boost their property value, Accessory Dwelling Units (ADUs) are becoming increasingly popular across California. Whether you’re considering adding a secondary living space for rental income, a home office, or a guest suite, building an ADU is a great option.
But the big question is: should you choose a prefab ADU in California or go for a custom ADU?
Each option has its pros and cons, and understanding the differences can help you make an informed decision. In this blog, we’ll break down the advantages and limitations of both prefab and custom ADUs and help you figure out which one fits your lifestyle, budget, and goals.
What Is a Prefab ADU?
A prefab ADU (short for prefabricated accessory dwelling unit) is a structure that is manufactured off-site, then transported and assembled on your property. These units come in various designs and sizes, often with fixed floor plans. Prefab ADUs have gained popularity for their efficiency and reduced build times.
What Is a Custom ADU?
A custom ADU, on the other hand, is designed and built entirely on-site based on your specific requirements. This type of ADU is tailored to match your main home’s architecture, personal preferences, and zoning regulations.
Prefab ADU California: Pros and Cons
Pros of Prefab ADUs
- Faster Build Time
One of the biggest advantages is speed. Since prefab units are built in factories while site work happens simultaneously, they can be installed in weeks compared to months for a custom build. - Lower Cost
A prefab ADU in California is typically more affordable than a custom one due to mass production, standard materials, and reduced labor costs. - Streamlined Process
Prefab companies often handle permits, delivery, and installation, making the process more straightforward for homeowners. - Consistent Quality
Factory settings ensure quality control and consistent output with less exposure to weather-related delays.
Cons of Prefab ADUs
- Limited Design Flexibility
You may be restricted to pre-designed floor plans, sizes, and layouts that might not suit your property’s shape or your family’s needs. - Zoning Challenges
Some municipalities have strict zoning and setback requirements that can limit where and how prefab units are installed. - Foundation & Utility Costs Still Apply
While the unit is prefab, site prep, utility hookups, and foundation work are still needed, which can increase total expenses.
Custom ADU: Pros and Cons
Pros of Custom ADUs
- Total Design Freedom
A custom ADU allows you to fully personalize the layout, finishes, and features—making it ideal for multigenerational living, luxury guest homes, or unique lifestyle needs. - Better Property Integration
Custom builds can seamlessly blend with your primary home’s architecture, landscaping, and neighborhood aesthetics. - Maximized Space Use
Designers can optimize awkward spaces, slopes, or small yards to get the most usable square footage out of your lot. - Tailored to Long-Term Use
Whether you’re planning a future home office, rental unit, or in-law suite, custom ADUs allow you to future-proof your investment.
Cons of Custom ADUs
- Longer Construction Timeline
Permitting, designing, and building can take several months—sometimes up to a year. - Higher Cost
Personalized materials, architectural plans, and site-specific engineering can make custom ADUs more expensive than prefab alternatives. - More Involvement
Custom ADUs require more decision-making and coordination with architects, builders, and city officials.
Which Is Better: Prefab or Custom ADU?
The decision between a prefab or custom ADU depends on your priorities:
| Criteria | Prefab ADU California | Custom ADU |
|---|---|---|
| Speed | Faster (weeks) | Slower (months) |
| Budget | More affordable | Higher investment |
| Design Flexibility | Limited | Unlimited |
| Customization | Minimal | Full customization |
| Permitting | Often included | Requires more coordination |
| Land Fit | Standard shapes, not always optimal | Designed to fit your unique property |
Legal and Zoning Considerations in California
California is one of the most ADU-friendly states in the U.S., but local jurisdictions like Corona, CA, may have additional requirements regarding setbacks, height limits, parking, and utility connections. Whether you’re building a prefab ADU in California or planning a custom ADU, ensure your design aligns with city guidelines.
This is especially important if you’re pairing your ADU project with a kitchen remodel in Corona, CA or other home upgrades. Combining permits for multiple projects can sometimes streamline the process and reduce overall costs.
Combining ADU Projects with Home Upgrades
Many homeowners in Corona, CA are leveraging the momentum of ADU construction to renovate other parts of their homes. For example:
- A kitchen remodel in Corona, CA can significantly increase your home’s value and make your property more rental-friendly.
- Upgrading your existing electrical or plumbing systems during ADU construction in Corona, CA can make both your main home and ADU more efficient and code-compliant.
Bundling projects with one trusted contractor helps save time, minimize disruption, and reduce overall expenses.
Final Thoughts: Making the Right Choice
If you’re looking for a quick, cost-effective solution with minimal involvement, a prefab ADU in California could be ideal. However, if you have a specific vision, unique lot, or want long-term flexibility, a custom ADU is worth the investment.
Your choice also depends on how you intend to use the ADU—whether as a rental income source, a family suite, or an extension of your living space. No matter which option you choose, having the right team by your side makes all the difference.
Build with Confidence
At South Star Construction, we specialize in both custom and prefab ADU construction in Corona, CA, helping homeowners create high-quality, functional living spaces that align with their budget, style, and needs. From kitchen remodels in Corona, CA to complete backyard transformations, we bring expertise, reliability, and precision to every project.
Ready to explore your ADU options? Contact South Star Construction today for a free consultation and let’s build something extraordinary together.