Modular ADU · California
Modular ADU California — Factory-Built, Fully Permitted
Epic Modulars builds modular ADUs in a certified California factory — starting at $79K all-in, permits included, 40% faster than site-built. Serving all 17 cities.
Modular ADU vs Site-Built — What Actually Matters
The legal outcome is identical. The experience is completely different.
Cost
Modular ADU
From $79K all-in
Site-Built ADU
$150K–$450K+
Timeline
Modular ADU
6–10 months
Site-Built ADU
12–24 months
Legal status in CA
Modular ADU
Same as site-built
Site-Built ADU
Same as site-built
Permit process
Modular ADU
Parallel — build during review
Site-Built ADU
Sequential — wait for approval
Build quality control
Modular ADU
Factory-controlled environment
Site-Built ADU
Weather & labor variability
Customization
Modular ADU
Curated floor plans
Site-Built ADU
Fully custom possible
Everything Included in Your $79K Modular ADU
No hidden fees, no surprise add-ons. One price covers it all.
Why Factory-Built Beats Traditional for ADUs
Three reasons California homeowners choose modular over site-built every time.
Predictable Cost
Factory production locks in material and labor costs before we break ground. No contractor markup surprises, no weather delays that push your budget. What we quote is what you pay.
Parallel Permitting
Your ADU is being built in the factory while your permits are in review. By the time the city approves, your unit is ready to ship. Site-built projects sit idle during that wait.
Controlled Quality
Factory-built means consistent labor in a climate-controlled environment — no moisture damage, no subcontractor variability, no shortcuts taken when the foreman isn't looking.
Modular ADU California FAQs
What is a modular ADU vs a prefab ADU?
The terms are often used interchangeably — both refer to accessory dwelling units built in a factory and then transported to your property. "Modular" technically means the unit is built in sections (modules) that are joined on-site, while "prefab" is a broader term covering any factory-built structure. All Epic Modulars ADUs are HCD-certified California factory-built units that meet the same building codes as site-built homes.
How much does a modular ADU cost in California?
Epic Modulars modular ADUs start at $79,000 all-in. That price includes permits, factory construction, delivery to your California property, installation on a permanent foundation, utility connections, and a 1-year workmanship warranty. Compare that to traditional site-built ADUs which typically run $150,000–$450,000+ in California — the savings come from factory efficiency, bulk materials, and parallel permitting.
How long does it take to build and install a modular ADU in California?
From signed contract to move-in, expect 6–10 months. The factory build takes 8–12 weeks. While your unit is being assembled, permits are simultaneously in review — this parallel process is the key time advantage. Once permits are approved and the build is done, delivery, set, and final connections take 4–6 weeks. Site-built ADUs typically run 12–24 months because construction cannot start until permits are issued.
What does the California modular ADU permit process look like?
Epic Modulars manages the entire permit process as part of your all-in price. We submit to your city's planning and building departments, handle plan check responses, and coordinate utility permits. HCD-certified factory plans are already pre-approved at the state level, which means local plan checkers have fewer questions — reducing review time by 2–8 weeks compared to custom site-built plans. Cities like San Jose have streamlined programs for factory-built ADUs.
How does a modular ADU compare to a site-built ADU?
Legally, they're identical — California treats HCD-certified factory-built ADUs the same as site-built for permits, property tax, and zoning. The differences are practical: modular ADUs cost 30–50% less, take 40% less time, and have more predictable quality because construction happens in a controlled factory environment with consistent labor. Site-built ADUs can be more customizable but cost significantly more and are subject to weather delays, labor shortages, and on-site variability.
Start Your Modular ADU Project Today
Epic Modulars handles design, permits, factory build, and installation. One call, one price, zero surprises.
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