Guide
What homeowners need to know.
Start With Feasibility
Before you compare builders, confirm ADU type, lot constraints, access, utilities, existing structures, and whether a garage conversion, attached unit, detached unit, or junior ADU makes sense.
Drawings and Permits
Most serious ADU paths require permit-ready drawings and supporting documentation. Your provider should explain what is included, who responds to city comments, and what consultants might be required.
Builder Questions
Ask how many similar San Jose ADUs the provider has completed, how they handle utilities, whether they provide drawings, and what budget assumptions are included.
Cost table
Use ranges until scope is real.
| Item | Planning range | Why it moves |
|---|---|---|
| Feasibility | Early planning | Confirms whether the project path is realistic. |
| Drawings | Pre-bid requirement | Needed for permits and meaningful bids. |
| Construction | After scope is defined | Depends on ADU type and site conditions. |
Mistakes
Avoid these expensive shortcuts.
- Assuming state ADU rules remove all local review
- Ignoring utility and access constraints
- Hiring a builder before clarifying who owns plans and permits
FAQ
Fast answers.
Can I rely on this page as legal advice?
No. Use it as planning guidance and verify current requirements with the city or a qualified professional.
What provider should I talk to first?
If you have no drawings, start with a planning, permit drawing, or design-build team that can review feasibility and cost.
What is the dumbest ADU shortcut?
Treating a contractor ballpark as a real budget before drawings, utilities, and site constraints are understood.