Accessory Dwelling Unit Cost Calculator

Because early estimates use typical assumptions. Final pricing depends on property-specific details like feasibility requirements, site access, grading, utility locations, and jurisdiction requirements.

The biggest cost drivers are usually:
• Steep slope, hillside conditions or difficult access
• Longer utility trenching runs (water/sewer/electrical)
• Upgraded finishes and custom details
• Demolition, tree removal, or unexpected site conditions
• Local jurisdiction requirements and inspection complexity

• New builds typically require full foundation/framing/utility runs.
• Conversions can be more cost-effective, but costs vary depending on existing structure condition, foundation, ceiling heights, and required upgrades.

Sloping or hillside sites may require additional grading, excavation, drainage solutions, and access coordination - which can increase cost and timeline.

• Public sewer may still require trenching distance and connection work.
• Septic projects can require additional planning, upgrades, or constraints depending on system capacity and local rules.

Not always. Smaller ADUs can have higher cost per sq ft because kitchens, bathrooms, utilities, and permits have fixed components. Larger ADUs often reduce cost per sq ft but increase total cost.

This estimate is intended to reflect typical and preliminary construction scope based on your selections. Your final scope may vary depending on design decisions, finishes, utilities, site work, and jurisdiction requirements specific to your lot.

These are market-based ranges and vary by neighborhood, layout, finish level, and local demand. Actual results depend on property specifics and market conditions.

Please book a consultation so we can review your property details (site access, utilities, slope, and scope) and provide a more tailored estimate to your specific lot and goals.