ADU & accessory dwelling units
What is the cheapest type of ADU to build?
A JADU (junior ADU) is the cheapest legal second unit in California — $35,000–$95,000 — because it reuses existing conditioned space and shares utilities with the main home. After JADU, garage conversions are next at $85K–$165K, then attached ADUs, then detached new builds.
Cost per sqft favors larger units; cost per dwelling favors smaller ones. If maximum rental income matters, model both: a 500 sqft JADU at $1,800/mo rent vs a 1,000 sqft detached ADU at $3,200/mo.
Prefab ADUs market low base prices but site work (foundation, utilities, permits, crane) typically adds $80K–$140K, narrowing the gap with site-built construction.
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Related questions
- • How much does a garage conversion cost?
- • Are prefab ADUs really cheaper?
- • Can I build an ADU for under $100K?
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