The most useful early ADU number is not a price per square foot. It is an all-in risk map that shows which costs are known, which costs are estimates, and which costs could change the decision.
Line items to include in an all-in ADU cost list
- Feasibility and due diligence: parcel review, zoning checks, title questions, utility calls, and early site assessment.
- Survey and site information: survey, grading information, drainage review, soils or geotechnical work if needed.
- Design and engineering: architectural design, structural engineering, civil engineering, energy code work, and plan revisions.
- Permits and fees: building permit, planning review, impact or utility-related charges, tap fees, school or transportation fees when applicable.
- Site work: demolition, grading, access, drainage, retaining walls, tree work, fencing, flatwork, alley improvements, and stormwater controls.
- Utilities: water, sewer, septic, electric, gas, meters, trenching, panels, service upgrades, and provider-specific requirements.
- Vertical construction: foundation, framing, envelope, mechanical, plumbing, finishes, appliances, and required specialty trades.
- Financing and carrying costs: loan fees, interest, appraisal, reserves, insurance, tax impacts, and owner time.
- Contingency: unknowns that are ordinary in small-site construction, especially when utilities and access are constrained.
- Operations: leasing, maintenance, property management, compliance, turnover, and long-term repairs.
The cheapest next step is usually verification
Before paying for full design, verify the question most likely to change the budget: utilities, access, local permission, or financing.
Civic Infill Works pairs policy and funding analysis with construction-readiness input from Alpine West Construction & Restoration when a client wants a deeper implementation path. Construction work and licensed trade work should be contracted separately with the appropriate professionals.