ADU cost starts with the site, not a generic number
ADU budgets are shaped by real property conditions, not only square footage. Access, utilities, existing structures, finish level, drainage, exterior assemblies, kitchen and bath scope, and inspection requirements can all change the construction path.
A useful ADU budget should explain the property conditions behind the price. BBC ADU reviews access, existing structures, utility routes, drainage, foundation or slab work, framing, kitchen and bath scope, exterior details, finish level, and inspection sequencing before treating the project as a number on a page.
The largest swings are often hidden at first
Two ADUs with similar square footage can price differently if one has easy access and short utility runs while another needs trenching, panel review, concrete repair, garage correction, or more exterior work. Finish level matters too, but homeowners should understand the construction and utility questions first. That helps the estimate show what is included, what still needs verification, and which choices can change the budget.
- Lot access and staging conditions
- Electrical, sewer, water, gas, and HVAC planning
- Garage condition or detached foundation needs
- Finish level, fixtures, flooring, cabinets, and exterior details
- Access, staging, demolition, and site preparation
- Sewer, water, electrical, gas, drainage, and rough plumbing
- Finish level, allowances, inspections, and final punch list
What a homeowner should understand before moving forward
The goal is not to guess a perfect number during the first conversation. The goal is to understand the ADU type, site constraints, utility work, finish direction, and permit path well enough to compare options with a realistic scope.
- Site conversationTalk through the property, intended use, budget direction, and timing.
- Property reviewLook at access, structure, utilities, drainage, layout, and the work area.
- Scope directionDefine the build path before drawings, permits, and finish selections move too far.
- Build coordinationMove through construction, inspections, finishes, and final corrections with one clear plan.