ADU FAQ California
ADU & Modular Home Questions, Answered
Everything California homeowners ask before building. If your question isn't here, just ask us.
General ADU Questions
What is an ADU?
An ADU (Accessory Dwelling Unit) is a secondary housing unit built on a residential property alongside a primary home. Also called a granny flat, in-law suite, backyard cottage, or secondary suite, ADUs can be detached, attached, or converted from existing space. California state law gives most homeowners the right to build at least one ADU on their property.
What's the difference between an ADU and a tiny home?
Tiny homes are typically 100–400 sq ft and are often designed to be movable (on wheels). ADUs are permanent structures built on a foundation and are subject to local building codes and permits — they become a permanent part of your property. Epic Modulars builds factory-built ADUs that are permanent, code-compliant, and permitted through the full California building permit process.
Can I rent out my ADU?
Yes. Renting out an ADU is one of the most common reasons California homeowners build them. You can rent it as a long-term rental, short-term rental (subject to local STR regulations), or to family members. California cities cannot require owner-occupancy for ADUs built after January 1, 2020.
Do I need to live on the property to build an ADU?
No. California law no longer requires owner-occupancy for most ADU types. You can build an ADU on a rental property or investment property. Some local jurisdictions may have additional requirements — we review this during your site assessment.
How many ADUs can I build on my property?
Under 2020+ California law, most single-family lots can have one attached ADU, one detached ADU, and one Junior ADU (JADU — converted from existing living space). Multifamily properties may qualify for additional units. Your exact allowance depends on lot size, zoning, and local regulations.
Permits & Legal
Do I need a permit to build an ADU in California?
Yes. All ADUs in California require a building permit. The permit process involves plan check, structural review, energy compliance (Title 24), and inspections. Epic Modulars handles the entire permit process in every jurisdiction we serve — it is included in your project price.
How long does the ADU permit process take in California?
Permit timelines vary significantly by city. Some cities offer over-the-counter approval or streamlined 30-day processing. Others — particularly in the Bay Area — can take 3–6 months for plan check. Epic Modulars is familiar with the process in all 17 cities we serve and will give you a realistic timeline estimate before you sign.
What are the ADU setback requirements in California?
California state law mandates that detached ADUs cannot be required to have more than a 4-foot rear and side setback for ADUs up to 800 sq ft. Larger ADUs or those in certain zones may have different requirements. Front setback rules vary by city. We assess your lot and confirm setback compliance during site evaluation.
Can my city reject my ADU permit application?
Under California law (AB 68, SB 9, AB 2221), cities have very limited ability to deny ADU permits for projects that meet state requirements. Most denials are due to incomplete applications or code non-compliance — not city opposition. If a city fails to act on a permit application within 60 days, it is deemed approved. We handle the entire process to ensure your application is complete and compliant.
What are the 2026 California ADU law changes?
California continues to expand ADU rights annually. Recent changes include streamlined permitting for ADUs under 750 sq ft, reduced or eliminated impact fees for ADUs under 750 sq ft, and additional protections against local restrictions. Our team stays current on all state ADU law and applies it to every project.
Cost & Financing
How much does an ADU cost in California?
Epic Modulars factory-built ADUs start at $79,000 all-in — including permits, delivery, installation, and warranty. Site-built ADUs in California typically range from $150,000 to $450,000+ for comparable units. Factory construction eliminates weather delays, reduces labor costs, and allows bulk material purchasing — savings we pass to you. See our full pricing guide for detailed cost breakdowns.
What financing options are available for ADUs?
The most common ADU financing options are HELOCs (home equity line of credit), cash-out refinancing, and ADU-specific construction loans. Fannie Mae HomeStyle and FHA 203k renovation loans also work for some buyers. Several California housing agencies offer below-market ADU loans for qualifying homeowners. We can refer you to ADU financing specialists.
Can I use a HELOC to finance an ADU?
Yes — a HELOC is one of the most popular ADU financing tools. If you have equity in your home, a HELOC lets you draw funds as needed during construction and typically offers lower interest rates than construction loans. With Epic Modulars' fixed pricing, you can use a HELOC with confidence knowing the total project cost before you start.
Do ADUs affect property taxes?
Adding an ADU in California triggers a supplemental tax assessment only on the new structure's value — your existing home is not reassessed under Prop 13. For a modest ADU, the additional annual property tax is typically $800–$2,000. Rental income from an ADU typically far exceeds this additional tax cost.
Are there grants or subsidies for ADU construction in California?
Yes. CalHFA offers the ADU Grant Program providing up to $40,000 toward pre-development and non-recurring closing costs for ADUs. Several cities and counties have their own programs. Income limits and program availability vary. We stay current on active programs and will let you know what you may qualify for during your consultation.
About Epic Modulars
What areas does Epic Modulars serve?
Epic Modulars serves homeowners across 17 California cities and the broader Bay Area and Central Valley regions, including San Jose, Santa Clara, Sunnyvale, Fremont, Oakland, Sacramento, Fresno, and more. We handle permits statewide — contact us to confirm service in your city.
How is a modular ADU different from a site-built ADU?
A modular ADU is built in a factory under controlled conditions, then transported to your property and installed on a permanent foundation. Site-built ADUs are constructed entirely on your property. Modular construction is typically faster (factory and site work happen simultaneously), more consistent in quality (factory QC vs. field conditions), and less disruptive to your daily life.
How long does it take from contract to move-in with Epic Modulars?
Total timeline is typically 6–10 months from contract signing to move-in. This includes permit processing (varies by city — 30 days to 4+ months), factory build time (8–12 weeks), site preparation, delivery, installation, and final inspections. We provide a project timeline at contract signing specific to your city and site.
What warranty does Epic Modulars offer?
Every Epic Modulars ADU includes a 1-year workmanship warranty covering defects in materials and installation. Factory-built components also carry manufacturer warranties for appliances, HVAC systems, windows, and other major systems — typically ranging from 2–10 years depending on the component.
Can I customize my ADU model?
Yes. Epic Modulars offers standard models with included finishes (LVP flooring, quartz counters, stainless appliances) and a range of upgrades — flooring, cabinetry, fixtures, exterior finishes, and more. For significant structural customization, contact us to discuss your specific requirements. Our team can walk you through available options during your initial consultation.
Want detailed pricing info?
Our ADU Cost Guide covers pricing tables, comparisons, and ROI calculations in depth.
Read the ADU Cost Guide →Still have questions?
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