The unit price is only one line. Here's the full picture — and why a factory-built ADU can beat a stick build on both cost and timeline.
When people ask what an ADU costs, they're usually quoting just the unit. The honest answer includes everything it takes to make that unit livable on your land — and that's where projects either stay on budget or blow up.
The line items that make up an ADU budget
- The unit itself — park models from roughly $121k–$133k; modular pods and domes quoted by configuration.
- Site work — clearing, grading and the foundation or pad.
- Utilities — water, power and either sewer tie-in or a septic system.
- Permitting & approvals — fees and the engineering some jurisdictions require.
- Delivery & installation — transport, set, and final connections.
Why factory-built often wins
A site-built ADU carries months of on-site labor, weather risk and schedule creep. A factory-built unit is constructed in parallel with your site work and installs in days once the pad is ready — compressing the timeline and reducing the surprises that drive overruns.
The return side
Because it sits on land you already own, an ADU skips the biggest cost in any housing project. A permitted, permanent unit can earn rental income and adds appraised value — which is what separates it from a depreciating trailer.
Last updated May 22, 2026
