What an ADU really costs in Reseda, all in

How much does a backyard house in Reseda cost all in?

There is no single price, but the published numbers give you a floor. An independent licensed general contractor's estimates, published by the plan company CALI ADU, run from $180,000 to $200,000 for a 400 sq ft studio up to $325,000 to $350,000 for a 1,000 sq ft three-bedroom ¹. Abodu, which sells factory-built units, lists an expected all-in from $298,800 that covers design, permits, the unit, delivery and installation ². Modative, a Los Angeles design-build firm, publishes a construction range of $99,000 to $399,000, with design, engineering and permits on top ⁵.

Reseda builds more of these than anywhere else in the Valley. ZIP 91335 had 254 ADU building permits in 2025, the most of the 36 San Fernando Valley ZIPs we track ⁷. The new detached ones are not small: the median new-construction ADU permit issued in 91335 since January 2025 lists 1,104 sq ft ⁷. The typical single-family lot they sit on is 6,639 sq ft, and half of Reseda's lots fall between 6,098 and 7,499 sq ft ³.

What does a price per square foot leave out?

Usually the plans, the city and the utilities. A per-square-foot number describes the building, and the building is only one line of the budget.

• Small units cost more per foot. The contractor estimates on CALI ADU's page work out to about $450 to $500 per sq ft for the 400 sq ft studio and about $325 to $350 per sq ft for the 1,000 sq ft plan ¹. A per-foot quote borrowed from a bigger project will undershoot a small one.
• Plans and permit processing are usually a separate bill. CALI ADU charges a fixed $7,490 to $12,990 for design, engineering, Title 24 energy work and permit processing ¹. Modative lists $20,000 to $30,000 for design, engineering and permitting ⁵.
• Utility work is priced by the utility, not the builder. A new water service, a panel upgrade and sewer work are covered below. CALI ADU's page does not say whether its build estimates include them, so ask any builder that question in writing.
• The valuation on the permit is not the price. The median new ADU permit in Reseda declares a valuation of $126,000, about $114 per sq ft ⁷. That is far below every builder estimate above. Do not budget from it.

How much are plans and city permits?

Plans run from about $7,490 with a fixed-fee plan company to $30,000 with a full-service design-build firm ¹⁵. City plan check and permit fees depend on the project, and LADBS publishes a fee estimate tool rather than a flat ADU price; the tool itself says its numbers are estimates based on the current fee ordinance and can change ⁹.

If you want a city plan check engineer's read before you pay for plans, LADBS sells a Preliminary Plan Check. It costs $208.00 plus a 3% Development Service Center charge and a 6% systems surcharge, paid before the appointment ⁸. That comes to about $227.

LADBS also runs a Standard Plan Program of pre-approved ADU plans. The city says using a standard plan shortens plan check and gets permits issued more quickly ¹⁰, but LADBS still reviews the plan against your property's zoning and foundation needs. A standard plan saves design time; it does not answer the questions about your own lot.

Do I need a new water meter, and what does it cost?

It depends on the kind of ADU, and if you do need one, it is $7,407. LADWP's charge for a new 1-inch domestic water service with a 1-inch intermediate meter is $7,143 for the service plus $264 for the meter, $7,407 in total, for fiscal year 2026/2027 ⁴. Many guides still quote $6,715; that was last year's figure ¹⁹.

State law decides when the utility can make you buy one. For an ADU built inside existing space, such as a garage conversion, the city or the water utility may not require a new or separate utility connection or charge a related connection fee, unless the ADU is built along with a new house or sold separately ¹¹. For a new detached backyard house, the utility may require a new or separate connection ¹². Some owners choose a separate meter anyway so a tenant can be billed directly; that is a choice, and it carries the same price.

What about the electrical panel, the sewer line and a soils report?

These are the three lines that most often move a Reseda budget, and each one depends on the lot rather than the building.

• Electrical panel. If the load calculation for your house plus the ADU is more than your existing service can carry, the panel gets upgraded. One Los Angeles electrical contractor puts a DWP panel upgrade at $3,500 to $7,500 ⁶.
• Sewer. Most backyard houses tie into the house's existing sewer line. If a new house connection to the street sewer is built instead, the Bureau of Engineering charges a Sewerage Facilities Charge of $344 per 100 gallons per day of average flow ¹⁶. If an existing house connection is extended, the city requires a camera (CCTV) inspection of the old line before it approves the extension ¹⁷. When the ADU sits at the back of the lot, that run to the street can be long, which is why the condition of the old line matters.
• Soils report. A Glendale geotechnical firm says that in the City of Los Angeles a full or modified soils report is typically required only on hillside lots, and that a modified report averages about $1,500 ¹⁸. Ask your designer early whether your lot will need one.

Will the city charge impact fees or school fees on my ADU?

Not on a small one. As of January 2026, state law (Government Code section 66311.5, renumbered by SB 543) says no local agency or utility may charge an impact fee on an ADU with 750 sq ft of interior living space or less; above 750 sq ft, impact fees must be charged in proportion to the size of the main house ¹³. Since the median new ADU permit in Reseda lists 1,104 sq ft ⁷, many Reseda owners are building above that line.

School fees follow a separate threshold. The same law says an ADU with less than 500 sq ft of interior living space counts as construction that does not add 500 sq ft of assessable space under the Education Code's school-fee rule ¹⁴. If your ADU is larger, ask LAUSD for its current residential rate before you set the budget.

What does an all-in budget look like for an 800 sq ft backyard house in Reseda?

Adding up only the sourced lines gives about $284,000 to $341,000, before LADBS plan check and permit fees and any proportional impact fees. We use 800 sq ft because state law lets a city cap a new detached ADU it must approve at 800 sq ft of living space ¹⁵.

1. Construction: $275,000 to $295,000, an independent contractor's estimate for an 800 sq ft plan ¹.
2. Plans, engineering and permit processing: $8,990 for that fixed-fee plan, up to $30,000 with a full-service design-build firm ¹⁵.
3. A new 1-inch water service, only if required or chosen: $7,407 ⁴.
4. A panel upgrade, only if the load calculation calls for it: $3,500 to $7,500 ⁶.
5. A modified soils report, only if one is required: about $1,500 ¹⁸.
6. LADBS plan check and permit fees: run your project through the city's estimator ⁹.
7. Sewer: nothing extra if the existing line serves the ADU; a Sewerage Facilities Charge and a permit if a new connection is built ¹⁶.

The low end assumes your lot needs none of items 3 through 5. The high end assumes it needs all three. Knowing which before you pay for plans is the kind of thing a lot check settles.

Quick answers

Sources

1. Signature ADU plans: plan fees and estimated cost to build, CALI ADU (plan company; builder-published estimate). Facts checked 2026-10-08
2. ADU guide: Los Angeles, Abodu (factory-built ADU seller). Facts checked 2026-10-08
3. Lot sizes of single-family parcels in ZIP 91335 (Greenlight analysis of the County Assessor parcel layer), Los Angeles County Office of the Assessor (data); Greenlight (method). Facts checked 2026-10-08
4. Schedule of Charges for Water Facilities, Fiscal Year 2026/2027 (Rev. 6/26), Los Angeles Department of Water and Power. Facts checked 2026-10-08
5. Los Angeles ADU process: consultation, design, build, permit, Modative / Mod EV (Los Angeles design-build firm). Facts checked 2026-10-08
6. DWP electrical panel upgrade, LA Pro Electrical (one contractor's published range). Facts checked 2026-10-08
7. ADU building permits issued in ZIP 91335 (Greenlight analysis of LADBS permit data), LADBS via City of Los Angeles Open Data (data); Greenlight (method). Facts checked 2026-10-08
8. Preliminary Plan Check, Los Angeles Department of Building and Safety (LADBS). Facts checked 2026-10-08
9. Plan Check Fee Estimate System, LADBS. Facts checked 2026-10-08
10. Accessory Dwelling Unit (ADU): Approved Standard Plans Program, LADBS. Facts checked 2026-10-08
11. Gov. Code §66311.5(d), as amended and renumbered by SB 543 (Stats. 2025, ch. 520), California Legislature (chaptered bill text, posted by LA County Planning). Facts checked 2026-10-08
12. Gov. Code §66311.5(e), as amended and renumbered by SB 543 (Stats. 2025, ch. 520), California Legislature (chaptered bill text, posted by LA County Planning). Facts checked 2026-10-08
13. Gov. Code §66311.5(c)(1), as amended and renumbered by SB 543 (Stats. 2025, ch. 520), California Legislature (chaptered bill text, posted by LA County Planning). Facts checked 2026-10-08
14. Gov. Code §66311.5(c)(3), as amended and renumbered by SB 543 (Stats. 2025, ch. 520), California Legislature (chaptered bill text, posted by LA County Planning). Facts checked 2026-10-08
15. Gov. Code §66323(a)(2), as amended by SB 543 (Stats. 2025, ch. 520), California Legislature (chaptered bill text, posted by LA County Planning). Facts checked 2026-10-08
16. Standard and associated fees, S-permits, City of Los Angeles Bureau of Engineering (BOE) Permit Manual. Facts checked 2026-10-08
17. S-permit processing procedures, City of Los Angeles Bureau of Engineering (BOE) Permit Manual. Facts checked 2026-10-08
18. ADU and garage conversions: geotechnical soil report, Applied Earth Sciences (Glendale geotechnical firm). Facts checked 2026-10-08
19. Schedule of Charges for Water Facilities, Fiscal Year 2025/2026 (Rev. 5/25), Los Angeles Department of Water and Power. Facts checked 2026-10-08

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.