Direct answer
The short version
ADU estimates are often wrong because they answer a smaller question than the homeowner is asking. A builder price may describe a structure, while the real project also includes site work, utilities, design, fees, corrections, and unknowns.
San Jose scope
Where this applies
This page is about San Jose homeowner decision risk. It does not accuse any builder and does not quote a universal San Jose price.
ADUOS checks
What we check first
- Whether the estimate includes site work and utilitiesModeled
- Whether permit and fee categories are consideredVerified
- Whether the path fits the parcelModeled
- Which exclusions could change the budgetNeeds review
- Whether the estimate should be treated as Modeled or Needs reviewModeled
What could change this
The answer can move
- Scope exclusionsNeeds review
- Utility upgrade requirementsNeeds review
- Plan-check commentsNeeds review
- Unknown drainage, foundation, or access constraintsNeeds review
Source notes
Why the label matters
Official sources can support process and fee categories. Builder estimate quality remains case-specific and should be checked against scope.
FAQ
Common follow-ups
Is the lowest ADU estimate the best estimate?
Not necessarily. The lowest number may exclude work that the homeowner still has to pay for later.
What should I ask a builder?
Ask what is excluded, what utility work is assumed, how permit corrections are handled, and what site conditions could change the price.