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Find Prefab and Modular ADU Contractors

Prefab ADUs are factory-built modular units delivered to your property and installed on-site. They offer 30–50% faster timelines than traditional builds, with costs starting at $80,000 installed.

3,311 contractors found

About Prefab ADU

Prefabricated ADUs are the fastest-growing segment of the ADU market, capturing over 50% of new installations. Factory-built ADUs offer consistent quality, faster construction (8–16 weeks on-site), and often lower costs than stick-built alternatives. Also called modular ADUs, these units are manufactured off-site and assembled on your property.

Typical Cost Range

$80,000 – $250,000

Timeline

8–16 weeks on-site

Prefab ADU Pros and Cons

Pros

  • +Fastest construction — 8–16 weeks on-site
  • +Consistent factory quality control
  • +Often lower cost than traditional stick-built ADUs
  • +Less on-site disruption during construction

Cons

  • Less design customization than stick-built
  • Delivery access — requires crane or truck access to your lot
  • Foundation and site prep still needed
  • Permit process is the same as traditional ADUs

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Frequently Asked Questions

How much does a prefab ADU cost?
Prefab ADUs range from $80,000 to $250,000 fully installed, depending on size and finishes. This typically includes the unit, delivery, foundation, utility connections, and installation.
How long does it take to install a prefab ADU?
On-site installation takes 8–16 weeks. However, the total timeline including permitting, site prep, and factory build is typically 4–8 months — still faster than traditional construction.
Do prefab ADUs need building permits?
Yes, prefab ADUs require the same building permits as site-built ADUs. The permitting process is identical, though some jurisdictions have pre-approved prefab ADU plans that speed up approval.
Are prefab ADUs as durable as stick-built?
Yes. Prefab ADUs are built to the same building codes as site-built homes. Factory construction often produces tighter tolerances and more consistent quality than field construction.

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