What an ADU in Los Angeles really costs.

California state ADU law recognizes four ADU types. Los Angeles follows the state framework and adds local plan-check requirements through the Los Angeles Department of Building and Safety, called LADBS for short. The four types are detached new construction, attached new construction, conversion of existing space such as a garage or basement, and Junior ADU, often called a JADU, which converts existing space inside the main house and is capped at 500 square feet.

Each pathway has different permit triggers, different setback rules, and different utility hookup requirements. A detached new build with its own water meter and sewer lateral runs the highest because it pulls a full structural permit, a separate utility connection, and full foundation work. A garage conversion runs lower because the foundation, the walls, and often the utilities are already there. A JADU runs lowest because no new exterior structure is built. The California Department of Housing and Community Development, called HCD for short, publishes the state-level rules and Los Angeles applies them through LADBS plan check.

When a builder gives you a bid, the first question to ask is which pathway the bid assumes. If the builder cannot tell you, the bid is not real. If the builder tells you and the pathway does not match your actual lot conditions, the bid will change once plan check comes back.

Past the permit pathway, seven concrete cost drivers swing a Los Angeles ADU bid. Walk through them with your builder in order. Each one moves the total by thousands, and the bids that look cheaper than the rest almost always shortchange one of these items.

1. Square footage. Bigger ADUs cost more, but the per-square-foot cost is not linear. The first 400 square feet carry the full foundation, kitchen, and bathroom cost. Square footage above that adds wall framing, flooring, and roof, which are cheaper per foot than the wet-room infrastructure.
2. Foundation type. A slab-on-grade foundation on level ground is the cheapest. A raised foundation on a sloped Hollywood Hills lot is significantly more because of grading, retaining, and structural engineering. Get the foundation type named in the bid.
3. Utility hookups. A new water meter, a new sewer lateral, and an upgraded electrical panel can each add four to five figures depending on the distance from the existing connection to the ADU pad. The Los Angeles Department of Water and Power, called LADWP, runs the water and power side. The water meter cost varies by service size.
4. Site access. If the ADU site is in the back of a long narrow lot with no truck access, hand-carrying materials raises labor cost. If the site is near the driveway, labor stays lower. Walk the site with the builder and watch them assess this.
5. Finish level. Stock cabinets, tile, and fixtures versus custom millwork, slab counters, and designer fixtures can double the per-square-foot finish line item. The structural cost stays the same. Decide your finish budget before the bid, not after.
6. Soft costs. Architectural drawings, structural engineering, Title 24 energy compliance, geotechnical reports if the lot requires one, and the LADBS plan-check fees. These are real costs that show up as line items on a real bid. If a bid shows zero soft costs, the bid is hiding them.
7. Contingency. A real ADU bid usually carries a contingency line, often in the 10 to 20 percent range, for what plan check comes back with, what the inspector flags during construction, and what gets discovered when the wall opens up. A bid with no contingency line is not protecting you from that risk, it is taking it.

A Los Angeles ADU from signed contract to certificate of occupancy usually runs 12 to 24 months. The plan-check phase alone runs months because LADBS reviews ADU plans through its standard plan-check queue, with revisions if the first submittal does not match code. State ADU law caps the LADBS review window once a complete application is submitted, but the gap between contract signing and a complete-and-accepted application is where most of the wait actually happens.

Real construction runs 4 to 8 months once permits are issued, depending on the four pathway type, weather delays, and inspection cadence. A builder who tells you the whole project will be done in 6 months from contract is either skipping plan check or planning to start construction before permits are issued, which is illegal and exposes you to stop-work orders. Ask for a written schedule that names plan-check submittal, plan-check approval, permit issuance, framing inspection, drywall inspection, and final inspection as separate milestones. If the builder cannot name those milestones, the schedule is not real.

If the lot is in a hillside grading area, in a fire severity zone, or in a historic preservation overlay, add review time. Each overlay triggers its own plan-check track. The Los Angeles Department of City Planning publishes the overlay maps.

A real ADU bid in Los Angeles is at least 8 to 12 pages. It names the pathway type. It names the square footage. It names the foundation type. It carries a soft-cost section that lists architectural, structural, Title 24, and plan-check fees as separate line items. It carries a hard-cost section with framing, roofing, electrical, plumbing, HVAC, drywall, flooring, cabinets, counters, fixtures, and finishes as separate line items. It carries an allowance section for items the homeowner picks late. It carries a contingency line. It carries a schedule of values that ties payment to milestones, not to calendar weeks.

A bid that fits on one page is not a bid. It is a guess. A bid that is significantly cheaper than the others almost always lives on that one page. Ask the cheaper builder for the line-item breakdown. If they cannot produce one, you have your answer.

When you compare bids, line items first, total last. Two bids 60,000 dollars apart usually have a foundation type difference, a finish allowance difference, or a missing soft-cost section. The total only tells you which builder is the cheapest. The line items tell you which builder is honest.

Three checks before any signature. First, verify the builder is licensed by the California Contractors State License Board, called CSLB. The CSLB license lookup is public and free. Check the license is active, the classification covers the work, and there are no open complaints. Second, verify the project pathway with LADBS. The LADBS website publishes the ADU information page and the permit application portal. You can pull pre-application questions there. Third, verify the bid against the same builder's previous Los Angeles ADU project at the same square footage and same pathway. Ask for the project address. Drive by. Knock on the door if the homeowner is willing.

If the builder cannot give you a previous Los Angeles ADU at the same scale, the builder is learning on your project. That is not always disqualifying, but the contingency should be higher and the schedule should reflect the learning curve. Price that in.

State and local ADU grant programs exist on and off. The California Housing Finance Agency, called CalHFA, ran an ADU grant program that was popular and got fully subscribed. Whether a similar program is currently funded changes from year to year and program to program. Before you bake a grant into your budget, verify the program is currently accepting applications at the official CalHFA ADU program page. Do not let a builder use a closed or speculative grant as part of the affordability story.

1. California Department of Housing and Community Development: Accessory Dwelling Units. State-level ADU law and ADU type definitions. Retrieved 2026-05-24.
2. Los Angeles Department of Building and Safety: ADU information. LADBS ADU pathway and permit application steps. Retrieved 2026-05-24.
3. City of Los Angeles Department of City Planning: Accessory Dwelling Units. Local zoning, setback, and overlay rules. Retrieved 2026-05-24.
4. LADBS Financial Services: fee overview. Published plan-check fee schedule, current as of the date the page was retrieved. Retrieved 2026-05-24.
5. Los Angeles Department of Water and Power. Water meter and electrical service connection authority. Retrieved 2026-05-24.
6. California Contractors State License Board: license lookup. Verify any builder by license number before signing. Retrieved 2026-05-24.
7. California Housing Finance Agency: ADU grant program. Verify current funding status before budgeting around any grant. Retrieved 2026-05-24.