Costs depend on the type of unit, the lot, the design and the work needed. This section explains the main cost categories so you know what to ask about.
What this topic covers
ADU cost has several layers: soft costs such as design and plan check, government fees and utility charges, hard construction costs, site work, and carrying costs such as loan interest. A quote that lists only construction leaves out many of them.
Key facts
- No government agency publishes a Los Angeles average ADU price. HCD publishes rules in the ADU Handbook, not typical costs.
- Converting existing space usually costs less than a new detached unit, because the foundation and framing already exist.
- Under Gov. Code 66311.5(c)(1), no impact fee may be imposed on an ADU of 750 square feet or less.
- Under section 66311.5(d), a utility cannot require a new connection or related fee for conversions and small units described in section 66323(a)(1).
- Compare bids only when each covers the same written scope, and ask what each excludes.
Guides in this hub
- ADU cost in Los Angeles: what drives the total, cost categories to look for in every bid, and how to compare bids.
- ADU impact fees and utility connections: the 750 square foot rule, school fees and who charges what.
Before you ask for bids
- Decide the unit type and a rough size.
- Send every builder the same plans and the same written scope.
- Ask for a line-item breakdown, not one lump sum.
- Ask the city or county what fees apply to your lot, and get the answer in writing.
Costs people miss
Budget for an electrical service upgrade for the main house, separate utility meters if the utility requires them, temporary power, change orders when the site holds surprises, and landscaping repair after heavy equipment. Fire zone lots must also meet stricter construction standards.
We do not quote prices or build ADUs. Use these pages to prepare questions for the professionals you choose.