Prefab ADU Cost in 2026
Prefab ADUs typically cost between $130,000 and $300,000 in 2026.
Typical range
$130k–$300k
Per sqft
$180–$350
Where the money goes
Line-item averages for a typical ADU build. Actual percentages vary by site conditions and finish level.
Foundation
$25k–$45kFraming & shell
$60k–$120kMechanical / electrical / plumbing
$35k–$70kFinishes
$30k–$90kPermits & impact fees
$10k–$30kDesign & engineering
$15k–$35kPrefab ADUs offer a specific tradeoff between cost, timeline, and flexibility. This guide breaks down typical pricing, line-item costs, and the key factors that affect your final budget.
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