ADU design quotes depend more on site and utilities than on a pretty floor plan you saw online. Treat the lot as the main character.
ADU-specific inputs
- Local ADU rules (size, height, setbacks, parking)
- Utility capacity (water, sewer/septic, power)
- Access path and fire requirements
- Slope, trees, and drainage
- Attached vs detached preference
What design fees typically cover
Programming, design, coordination with engineers as needed, and permit documents — confirm exclusions like surveys, soils, and energy consultants.
Cost drivers unique to ADUs
Utility runs, foundation conditions, and jurisdiction review cycles can outweigh interior finishes in early budgets.
Matching tip
Note “ADU” clearly in your project type and city. Firms with local ADU experience save months of false starts.