ADU Property Feasibility Pathway
A secondary dwelling connected to an existing residential property, usually reviewed through state ADU law and local objective standards.
What this project type usually means
Detached, attached, or conversion housing on a parcel with an existing or proposed primary dwelling.
Why this path can be easier or harder
ADUs often have a clearer starting framework, but setbacks, utilities, fire access, coastal, historic, hillside, and existing site conditions still matter.
First jurisdiction question
Is the parcel inside city limits, or does unincorporated county planning handle ADU review?
Zoning questions
- Which local ADU ordinance applies?
- What objective standards affect setbacks, height, size, lot coverage, and parking?
- Do overlays change normal ADU review?
Utility questions
- Can sewer, water, and electric service support the ADU?
- Are meter, panel, lateral, or connection upgrades likely?
- Does public works need to review frontage or drainage?
Septic and well questions
- If sewer is unavailable, can environmental health review the added wastewater demand?
- Is there leach-field and reserve area for an ADU?
Fire and access questions
- Does the fire authority need driveway, turnaround, hydrant, fire-flow, or address marker review?
- Does WUI construction apply?
Overlay questions
- Coastal
- Historic
- Hillside
- Fire hazard
- Floodplain
- HOA or private covenants
Documents to collect
- APN
- Site plan
- Existing floor plan
- Utility notes
- Prior permits
- Zoning lookup
- Photos of access and existing structures
Departments to contact
- Planning
- Building
- Fire authority
- Utility providers
- Public works
- Environmental health if septic or well applies
Before You Hire or Request an Estimate
- Identify jurisdiction and collect the APN.
- Confirm the zoning starting point and local ADU rules.
- Collect photos of the site, access, utilities, and existing structures.
- Know whether you are comparing detached, attached, garage conversion, or JADU scope.
- Ask whether design, permits, engineering, construction, utility coordination, and sitework are included.
- Ask what is excluded and what city-specific ADU experience the builder has.
Common mistakes
- Assuming state ADU law removes site limits
- Ordering plans before confirming utilities
- Ignoring unpermitted prior work
- Missing fire or public works review
Questions to ask before spending money
- What ADU type fits the parcel?
- Which standards will staff apply?
- What utility upgrades could change the budget?
- What documents should a designer see first?
Related county guides
Related city guides
Related learning guides
Before you hire guides
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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.