Before You Hire
How to Prepare for an ADU Estimate
Organize the property facts, photos, utility notes, and project scope details that make early ADU estimates more useful.
Why estimate quality depends on information quality
An early estimate is only as useful as the property facts behind it. Builders need the address, APN, jurisdiction, existing conditions, desired ADU type, utility clues, photos, and known constraints before assumptions become meaningful.
Information to collect before asking
Collect address, APN, city or county, existing home size, lot size if known, garage dimensions if conversion, desired ADU size, detached/attached/conversion preference, utility locations, sewer or septic status, known overlays, budget range, and timeline.
Photos to gather
Photograph the street view, driveway or access, backyard or proposed site area, garage interior and exterior, electrical panel, gas meter, water or sewer cleanout if visible, slope, drainage, trees, and obstructions.
Questions before trusting the estimate
Ask what property facts were assumed, what utility and sitework costs are excluded, what permit scope is included, whether plan-check corrections are included, and what local department questions still need confirmation.
What early estimates may exclude
Early estimates may exclude sewer laterals, water upgrades, panel upgrades, trenching, septic changes, grading, drainage, retaining walls, tree removal, demolition, permit fees, engineering, energy forms, fire sprinklers, or finish upgrades.
Practical checklist
Use this topic to organize a parcel-specific checklist before spending money: identify the APN, confirm jurisdiction, verify zoning and overlays, check utility and access facts, collect official links, and record department responses.
Red flags to watch
Treat the project as higher uncertainty if jurisdiction is unclear, utilities are not confirmed, sewer is unavailable, septic or well review is needed, the parcel is rural, road access is private, or fire, flood, coastal, slope, habitat, agricultural, or easement constraints may apply.
- Call planning before buying land or ordering plans.
- Ask building how the structure type will be reviewed.
- Confirm utility providers and connection feasibility.
- Check environmental health for septic and well issues.
- Ask the fire authority about access, hydrants, fire flow, WUI, and defensible space.
- Save links, names, dates, and code references.
Official verification
Use this article as an educational starting point only. The actual answer depends on parcel facts, local interpretation, official maps, utilities, fire authority standards, environmental health review, and building department requirements.
Frequently Asked Questions
Is there one statewide answer for this issue?
No. California rules create starting points, but parcel-specific local confirmation is required.
Which department should I contact first?
Start with the planning department for the parcel's city or unincorporated county area, then confirm building, utility, environmental health, and fire authority requirements as needed.
Can I rely on this guide instead of contacting local officials?
No. Use this guide to organize questions and documents, then confirm the answer directly with the appropriate local departments before spending money or submitting plans.
Related next steps
Related project pathways
Related county guides
Related city guides
Related articles
Review Next Steps
Use the county, city, and learning guides to organize zoning, utility, septic, fire access, estimate-readiness, and permit questions before buying land or choosing a design.
TinyHomeNavigator provides educational information only. Rules vary by parcel, zoning district, city, county, overlay, utility provider, fire authority, and environmental health department. Always confirm directly with the local planning department, building department, environmental health department, fire authority, and utility providers before buying land, designing, permitting, placing, or building any structure.