Short answer
San Jose costs depend heavily on project type and permit path. ADU and addition planning usually benefits from early feasibility before a full architecture fee is quoted.
| Item | Planning range | Notes |
|---|---|---|
| San Jose ADU feasibility | $500-$3,000 | Site constraints, utilities, and zoning checks first. |
| Garage conversion drawings | $4,500-$14,000+ | Existing condition documentation matters. |
| Addition design and permits | $15,000-$50,000+ | Depends on structural scope and planning triggers. |
How to use these numbers
Treat the ranges as planning context, not a quote. Bay Area homes punish lazy assumptions: existing conditions, utilities, structural scope, planning review, and consultant needs can move the number fast.