Most people ask one question first: what will an ADU cost? The honest answer is that no government agency publishes a Los Angeles average. Prices come from contractors, and they vary with the unit, the lot, and what a quote includes.
LA ADU Guide is an information site. We do not design, build or finance ADUs. This guide shows what drives the total so you can read a quote with confidence.
Why there is no single number
The state housing department (HCD) publishes the ADU Handbook, which covers rules. It does not set a typical price. The numbers you see online come from builders and marketing pages. Several 2026 contractor pages we reviewed gave ranges that disagreed widely, and some pages looked unreliable. We do not repeat dollar figures we cannot trace to a named, dated source.
Use any per square foot number you find as a rough estimate only. Ask what it covers. Many quotes list construction only and leave out design, engineering, permits, fees, appliances and site work.
What changes the price
These factors move the total more than anything else.
- Type of unit. Converting a garage or existing space usually costs less than building a new detached unit, because the foundation and framing already exist. See ADU vs JADU vs garage conversion.
- Size. Bigger units cost more in total, but often less per square foot. Fixed costs get spread over more area.
- Site conditions. Slope, soil, access for equipment, trees and old utility lines all add work.
- Utility distance. The farther the new unit is from the main house connections, the more trenching and piping.
- Fire zone. Homes in a fire hazard severity zone must meet stricter construction standards. See ADUs in fire hazard zones.
- Finishes and systems. Kitchen, bath, flooring, windows and HVAC choices.
- Prefab or site built. Factory built units shift some cost to the factory and some to site work. See prefab and preapproved ADU plans.
Cost categories to look for in every bid
Ask each builder to price these separately. If a line is missing, ask whether it is included, excluded or "by owner."
Soft costs
- Design and drawings
- Structural, energy (Title 24) and soils reports
- Survey
- City plan check and permit fees, covered in our permit process guide
Government fees and utility charges
- Impact fees. Under Gov. Code 66311.5(c)(1), no impact fee may be imposed on an ADU of 750 square feet or less. Larger units are charged proportionately to the main home.
- Utility connection fees and capacity charges. These depend on the type of unit. Details are in ADU impact fees and utility connections.
Hard costs
- Demolition and site prep
- Foundation, framing, roofing
- Plumbing, electrical, HVAC
- Insulation, drywall, windows, doors
- Kitchen, bath, flooring, paint
Site and extras
- Trenching and utility lines
- Electrical panel upgrade
- Landscaping, paving, fencing
- Retaining walls on sloped lots
- Fire sprinklers, where required
Carrying costs
- Interest on a construction loan
- Builder's risk or other insurance
- Your own rent or mortgage if the work delays a move
Cost categories at a glance
| Category | Examples from this guide | Where to read more |
|---|---|---|
| Soft costs | Design, structural, Title 24 and soils reports, survey, plan check fees | Permit process |
| Government fees | Impact fees (none at 750 sq ft or less), utility connection charges | Impact fees |
| Hard costs | Foundation, framing, plumbing, electrical, HVAC, finishes | Ask each builder for a line item |
| Site and extras | Trenching, panel upgrade, retaining walls, fire sprinklers where required | Fire zones |
| Carrying costs | Construction loan interest, insurance | Financing |
Costs people miss
Budget for these before you sign a contract.
- An electrical service upgrade for the main house
- Separate utility meters, if the utility requires them
- Temporary power, portable toilets and permit-related inspections
- Change orders when the site holds surprises
- Landscaping and driveway repair after heavy equipment
- Furniture and appliances if you plan to rent the unit
How to compare bids
- Send every builder the same plans and the same written scope.
- Ask for a line-item breakdown, not one lump sum.
- Check what is excluded. Allowances (a fixed budget for tile, fixtures or appliances) are where totals grow.
- Ask who pays permit fees and utility charges, and when.
- Confirm the contractor's license on the state board site. Our CSLB check guide shows how.
- Get a payment schedule tied to finished work. California law limits down payments on home improvement contracts. Check the current limit at the CSLB site.
Money that may lower the net cost
Some programs have helped homeowners with up-front costs. The CalHFA ADU Grant Program offered up to $40,000 for pre-development costs, and a January 2025 state report says a second phase was funded with $25 million for lower-income homeowners. Funds were handled through partner lenders. Check CalHFA directly for current status before you plan around it. See ADU financing options.
Quick checklist
- [ ] Decide the unit type and rough size
- [ ] Ask for line-item bids from at least three licensed contractors
- [ ] Confirm what each bid excludes
- [ ] Ask the city or county what fees apply to your lot
- [ ] Add a cushion for surprises
- [ ] Review financing and tax effects before you commit
What to remember
- No official Los Angeles ADU price exists. Treat online averages as rough.
- Scope decides the number. Compare the same scope.
- Fees and utility charges are separate from construction. Learn them early.
Rules and fees change. Confirm with LADBS, LA City Planning or your own building department before you budget. See the ADU costs hub for related guides.
For real permit data on declared costs by year, type and area, see What 41,000 LA ADU permits show about size, declared cost and time.