Prefab (prefabricated) ADUs are built in a factory and delivered to your property, where they are installed on a prepared foundation. This approach offers faster timelines, consistent quality, and increasingly competitive pricing.
Why Choose Prefab?
Faster Timeline
Factory construction takes 6-12 weeks. Total project time is typically 4-8 months vs. 8-14 months for traditional builds.
Cost Savings
Prefab can save 20-40% compared to traditional on-site construction due to factory efficiencies and reduced labor costs.
Quality Control
Built indoors with precision tooling. No weather delays, consistent quality, and often higher energy efficiency ratings.
Prefab ADU Costs
| Size | Unit Cost | Site Prep & Install | Total Installed |
|---|---|---|---|
| 200-400 sq ft (Studio) | $50K-$100K | $25K-$50K | $75K-$150K |
| 400-600 sq ft (1BR) | $80K-$140K | $35K-$60K | $115K-$200K |
| 600-800 sq ft (2BR) | $100K-$180K | $40K-$70K | $140K-$250K |
| 800-1,200 sq ft (2-3BR) | $130K-$220K | $50K-$80K | $180K-$300K |
Important: "Installed" Cost
Always ask for the total installed cost, not just the unit price. Site preparation (foundation, utility connections, permits, crane delivery) typically adds $25,000-$80,000 to the base unit price.
The Prefab ADU Process
Choose Your Model
Select a design and floor plan from a manufacturer. Most offer customization options for finishes, layouts, and features.
Permits
Submit plans to your city. Some manufacturers handle permitting for you. California's 60-day review timeline applies.
Site Prep
While your ADU is being built in the factory, a contractor prepares the foundation and utility connections at your property.
Factory Build
Your ADU is constructed in a climate-controlled factory. Typical build time: 6-12 weeks.
Delivery & Install
The completed unit is transported to your property by truck and set on the prepared foundation by crane.
Final Connections
Local contractors connect utilities, complete exterior finishes, and handle landscaping. Final inspections follow.
Finance Your ADU Project
Most ADU projects are funded through HELOCs, construction loans, or cash-out refinancing. Compare rates from top lenders in minutes.
Compare ADU Financing Options →Compare Prefab ADU Options
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