The soft costs of an ADU in Los Angeles, line by line

What counts as a soft cost on an ADU?

A soft cost is any line that is not labor and materials for the building. A per-square-foot build price usually leaves them out.

• Design and engineering: architectural drawings, structural engineering and the Title 24 energy calculations.
• City fees: LADBS plan check and permit fees, plus clearances from other departments such as the Fire Department and the Bureau of Engineering.
• School and impact fees: set by state law and by the school district, and tied to the size of the unit.
• Utility and site work: a water service, an electrical panel upgrade, sewer work, a soils report or a survey, each only if your lot needs it.

Size matters more than most owners expect. We pulled every new-construction ADU permit LADBS issued in the 36 San Fernando Valley ZIP codes we track from January 2025 to early October 2026: 1,626 permits, with a median size of 1,064 sq ft and a median declared valuation of $120,000 ⁸. Of those, 1,251 were larger than 750 sq ft ⁸. That number matters for the fee sections below.

How much do plans, engineering and Title 24 cost?

Published prices for a full plan set in Los Angeles run from $7,490 to about $30,000. CALI ADU, a plan company, charges a fixed $7,490 to $12,990 that it says covers design, engineering, Title 24 and permit processing ¹. Modative, a Los Angeles design-build firm, lists $20,000 to $30,000 for design, engineering and permitting ².

What drives the price is what the city requires on the drawings. LADBS's submittal requirements for new ADU plans ask for plans signed and stamped by a California-licensed architect or engineer, with one exception: a one-story wood-frame ADU designed to the city's prescriptive wood-frame provisions does not need the stamp ³. The same list includes energy calculations and forms for Title 24 ³.

The energy rules changed this year. As of January 2026, the 2025 Energy Code applies to building permit applications submitted on or after January 1, 2026, and the state says all newly constructed buildings require a newly installed solar PV system ⁴. Duct leakage testing and other checks must also be field-verified by an ECC rater ⁴. Ask in writing whether the build price includes the solar array and the testing.

If you use a plan from the city's pre-approved list, the design bill can shrink; see our guide to LA standard ADU plans.

What does LADBS charge for plan check and permits?

LADBS does not publish a flat ADU price, because its fees are based on the valuation of the work. The city's Housing Element says permit fees are based on the total value of all construction work for which the permit is issued ⁵. Its own sample for a new 1,200 sq ft one-story ADU with a $121,200 valuation came to a total permit fee of $8,447.62, and a 400 sq ft garage conversion at a $20,000 valuation came to $1,045.22 ⁵. Those samples come from the 2021-2029 Housing Element, so treat them as a guide to scale.

A plan company's 2023 worked example lands in the same place: about $1,496 in LADBS fees for a garage conversion valued at $75,000, and about $7,479 for a 1,200 sq ft detached ADU valued at $150,000, a total it says included a school district fee and an energy surcharge ⁶. The same page lists $300 for the Fire Department's hydrant and access review and $670 for the Bureau of Engineering's sewer availability check ⁷.

The median new ADU permit in the Valley declares $120,000 ⁸, close to the city's own $121,200 sample. For your own number, run the project through the LADBS fee estimator, which says its figures are estimates under the current fee ordinance and can change ¹⁸. If you want a city plan check engineer's read before you pay for plans, a Preliminary Plan Check costs $208.00 plus a 3% Development Service Center charge and a 6% systems surcharge ¹⁶. How long plan check takes is covered in our plan check timeline guide.

Will I pay school fees or impact fees on my ADU?

Probably, if you build at the size most Valley owners are building. State law, as amended by SB 543, bars impact fees only on an ADU with 750 sq ft of interior living space or less; above that, impact fees must be charged in proportion to the size of the main house ⁹. In our Valley permit pull, 1,251 of 1,626 new ADUs were above 750 sq ft ⁸.

School fees follow a lower line. An ADU with less than 500 sq ft of interior living space is treated as construction that does not add 500 sq ft of assessable space under the Education Code ¹⁰, so a small unit escapes them. A larger one does not. On January 28, 2026 the State Allocation Board raised the statewide maximum school fee on residential construction from $5.17 to $5.38 per square foot ¹¹. At that ceiling, a 1,064 sq ft ADU would pay at most about $5,724. LAUSD sets its own rate at or below the cap; see our LAUSD school fee guide for the current figure.

Which utility and site costs show up after the plans are drawn?

These lines depend on your lot, not the building, and a design quote rarely includes them.

• Water service. If LADWP requires or you choose a new 1-inch service with a 1-inch meter, the fiscal year 2026/2027 charge is $7,407 ¹². When one is required is explained in our water meter guide.
• Electrical panel. One Los Angeles electrical contractor puts a DWP panel upgrade at $3,500 to $7,500 ¹³. Whether the load calculation calls for one is covered in our 200-amp panel guide.
• Sewer. Whether the existing line can serve the unit, and how far it is to the city main, decide this line; see our sewer guide.
• Fire access. For new construction valued at $50,000 or more, LADBS requires fire lane access where any part of the building is 150 ft from the edge of an improved street, and a clearance from the Fire Department's Hydrants and Access Unit ¹⁷.
• Soils report. A Glendale geotechnical firm says that in the City of Los Angeles a soils report is typically required only on hillside lots, and that a modified report averages about $1,500 ¹⁴.
• Survey. One San Diego builder treats a boundary survey as case-by-case, depending on city requirements and where the unit sits, and publishes $2,500 to $12,500 for one ¹⁵. We found no Los Angeles surveyor publishing a price.

What do the soft costs add up to on a new backyard house?

Adding only the published lines above gives about $16,000 at the low end and about $74,000 if a lot needs everything. These are sums of other people's published numbers, not a quote.

Low end, about $16,000: a $7,490 fixed-fee plan set ¹, about $7,479 in LADBS fees on the 2023 example that included the school fee ⁶, and $970 for the Fire Department and sewer availability reviews ⁷. No new water service, no panel upgrade, no soils report, no survey.

High end, about $74,000:

1. Full-service design, engineering and permitting: $30,000 ².
2. LADBS permit fees on the city's 1,200 sq ft sample: $8,447.62 ⁵.
3. School fees at the state ceiling on a 1,064 sq ft unit: about $5,724 ¹¹.
4. Fire Department and sewer availability reviews: $970 ⁷.
5. A new 1-inch water service: $7,407 ¹².
6. A panel upgrade: up to $7,500 ¹³.
7. A modified soils report: about $1,500 ¹⁴.
8. A boundary survey at the top of one builder's range: $12,500 ¹⁵.

Most lots land in between, and which of items 5 through 8 apply is the part you can find out before you pay for plans. That is the kind of thing a lot check settles. For the build side of the budget, see what an ADU costs in Reseda.

Quick answers

Sources

1. Signature ADU Plans, CALI ADU (plan company). Facts checked 2026-10-09
2. Los Angeles ADU process: consultation, design, build, permit, Modative (Los Angeles design-build firm). Facts checked 2026-10-09
3. Document Submittal Requirements for New ADU Standard Plans (IB P/GI 2023-032), LADBS. Facts checked 2026-10-09
4. 2025 Energy Code: Accessory Dwelling Units (ADU), California Energy Commission. Facts checked 2026-10-09
5. Housing Element 2021-2029, Appendix 2.4: Summary of Case Filing and Building Permitting Fees, Los Angeles City Planning. Facts checked 2026-10-09
6. How much does an ADU permit cost in Los Angeles? (June 22, 2023), CALI ADU (plan company; worked example). Facts checked 2026-10-09
7. How much does an ADU permit cost in Los Angeles? (June 22, 2023), CALI ADU (plan company; worked example). Facts checked 2026-10-09
8. Building Permits Issued (dataset pi9x-tg5x), LADBS via City of Los Angeles Open Data (data); Greenlight (method). Facts checked 2026-10-09
9. SB 543 (Stats. 2025, Ch. 520), chaptered text, Attachment A to LA County ADU memo, California Legislature (posted by LA County Planning). Facts checked 2026-10-09
10. SB 543 (Stats. 2025, Ch. 520), chaptered text, Attachment A to LA County ADU memo, California Legislature (posted by LA County Planning). Facts checked 2026-10-09
11. Annual Adjustment to SFP Grants and Developer Fee History, California Department of General Services, Office of Public School Construction (State Allocation Board). Facts checked 2026-10-09
12. Schedule of Water Facility Charges 2026-2027, LADWP. Facts checked 2026-10-09
13. DWP Electrical Panel Upgrade, LA Pro Electrical (one contractor's published range). Facts checked 2026-10-09
14. ADU and garage conversions: geotechnical soil report, Applied Earth Sciences (Glendale geotechnical firm). Facts checked 2026-10-09
15. When do you need a survey for an ADU?, Snap ADU (San Diego ADU builder). Facts checked 2026-10-09
16. Preliminary Plan Check, LADBS. Facts checked 2026-10-09
17. ADU Plan Check Correction Sheet, LADBS. Facts checked 2026-10-09
18. Plan Check and Permit Fee Estimate, LADBS. Facts checked 2026-10-09

Greenlight is not a contractor, architect or engineer, and this is not legal advice. Rules change; every fact here shows the date we last checked it.