ADU Construction Cost in Los Angeles

Price sources checked October 13, 2026. LADU gives $150,000–$400,000-plus for Los Angeles ADUs generally. Construction Consulting Services lists $200,000–$480,000 for detached units of 700–1,200 square feet. These are the companies’ own planning examples with different scopes, not government price data or quotes for your property.

The gap between those figures is useful. There is no honest one-price answer without a site and a written scope. This site does not provide building quotes.

Garage Conversion, Detached and Attached ADU Costs

A garage conversion may reuse walls and a roof. It can still need work on the slab, frame, moisture and fire safety. Energy and utility upgrades may also be needed. A detached ADU needs a new base, frame and outer shell. An attached or upper-floor unit adds work around an occupied home. Hillside, coastal, historic, fire-zone and tight sites need their own plan.

Do not compare a small interior conversion with a ground-up two-bedroom unit by square-foot rate alone.

ADU Design, Engineering and Permit Costs

1. Property check and property details

Allow for record research and a check of the permit office. Add site measurements, a survey if needed and review of title or easements. Include early utility checks and expert advice. This work can stop a design from using the wrong facts.

2. Design, engineering and energy documents

List building design, structural work and energy forms. Add drainage, soil and geology work if needed. Include heating, power and plumbing plans, plus revisions. Ask if images, finish choices and replies to permit notes are included.

3. Applications, plan check and agency charges

Separate public and utility fees from the company’s permit-service fee. Record who pays each bill. Local steps differ, so do not reuse one city’s fee estimate for another.

Site Work, Structure and Utility Costs

4. Demolition, access and site preparation

Include removal work and protection for the occupied home. Add temporary needs, storage, hauling, digging and grading. Include shoring, retaining walls, soil handling and repairs. Narrow access can require more work by hand.

5. Foundation, structure and exterior envelope

This section covers concrete or another approved foundation system, framing, roof, windows, exterior doors, weatherproofing, insulation, cladding and exterior coatings. Verify whether gutters, drainage connections, decks, steps and exterior lighting are included.

6. Building systems and utilities

List electric service, panel work and wiring. Add heating, cooling, vents, plumbing and hot water. Include sewer, water, gas if used, fire sprinklers if required and data lines. The utilities guide explains why trench length and current capacity matter.

ADU Finishes, Appliances and Property Restoration

7. Interiors, fixtures and appliances

Use a written finish list. State cabinet length, counter type, tile area and plumbing brands. Add the number of lights, flooring, doors, trim, paint, appliances and hardware. “Standard finish” is not enough detail.

8. External work and property repairs after construction

Include paths, fencing, gates, planting, irrigation repair, drive or paving repair, drainage, refuse areas and work around the main house. A quote that stops at the ADU wall may not deliver a usable finished property.

9. Contingency and owner costs

Keep extra money for named risks. Existing buildings and buried lines have more unknowns than an open site that has been checked. List loans, insurance, temporary housing and owner advisers on separate lines. Do the same for items bought by the owner.

ADU Cost Per Square Foot: What Is Included?

A kitchen, bathroom, electrical service and utility connection create substantial fixed costs. A smaller unit can therefore cost more per square foot. Published rates may include only construction, while others include design and permits. Site work may be excluded or carried as an allowance.

If a company gives a rate, ask what it divides. Record the contract total and floor area used. List every group that is included or left out.

Comparing ADU Quotes on the Same Scope

California’s Contractors State License Board advises owners to collect three or more written quotes that use matching drawings and specifications. Transfer them into a side-by-side schedule with one row for every budget section above.

Record the items below for each quote.

• exact plans and revision date priced;
• fixed amounts versus allowances;
• permit, utility and agency charges;
• exclusions and owner-supplied work;
• payment milestones;
• change-order markup and concealed-condition process;
• start and completion assumptions; and
• warranty and final approval deliverables.

The lowest total may simply have the most unpriced rows.

ADU Deposits, Payments and Change Orders

CSLB’s home-improvement contract guidance says covered home-improvement projects over $500 need a written contract. Confirm which contract rules apply to your proposed ADU work. Its normal down-payment limit is $1,000 or 10% of the contract price, whichever is less. Work and price changes should use signed change orders. Check current CSLB rules and any legal exceptions before signing.

Tie later payments to clear work or delivery milestones. Do not let a payment schedule get far ahead of completed work.

Building a Property-Specific ADU Budget

Replace one headline total with a clear test. State the unit type and rough size. Add the address, access, utility assumptions and finish level. Keep extra money for named risks. Update the budget as facts improve.