How much does an ADU cost in Granada Hills?

How much does a backyard house in Granada Hills cost all in?

There is no single price, but published numbers set a floor. Estimates by an independent licensed general contractor, published by the plan company CALI ADU, run $275,000 to $295,000 for an 800 sq ft unit, $325,000 to $350,000 for a 1,000 sq ft one-story, and $385,000 to $420,000 for a 1,200 sq ft two-story 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 ³.

Granada Hills owners tend to build toward the top of those size ranges. The city issued 104 permits for new ADU buildings in 91344 from January 2025 to early October 2026, not counting supplemental permits. The median one lists 1,036 sq ft, the middle half run from about 775 to 1,200 sq ft, and 65 of the 104 are larger than 800 sq ft ⁵. See also ADU permits by ZIP and what an ADU costs in Reseda.

My lot is bigger than most in the Valley. What does that let me build, and what does it cost?

It mainly lets you build a bigger unit, and a bigger unit costs more. The median single-family lot in Granada Hills (91344) is 8,345 sq ft, and half of them fall between 7,524 and 11,393 sq ft; the median house on them is 1,786 sq ft ⁴.

Two size rules matter. State law guarantees a detached backyard house of up to 800 sq ft with four-foot side and rear setbacks ⁷. Los Angeles's own ADU ordinance allows a detached unit of up to 1,200 sq ft and two stories, with more conditions attached ⁶.

Going from 800 to 1,200 sq ft adds about $110,000 to $125,000 in build cost on one contractor's estimates ¹. Size also changes fees. State law bars impact fees on an ADU of 750 sq ft of interior living space or less; above that, impact fees are charged in proportion to the size of the main house ⁹. School fees follow their own threshold, explained in school fees on an ADU in LA.

Is an attached ADU cheaper than a detached one?

Usually it is a smaller project, so its total is lower, but we could not find a published Los Angeles price comparison for the same size unit. What the city's permit records show is the declared valuation each owner put on the permit, which is not the price you will pay but does show the gap between project types ⁵.

• New detached buildings: 104 permits in 91344 since January 2025, median 1,036 sq ft, median declared valuation $120,000 ⁵.
• Additions (attached units, and garage conversions that add space): 63 permits, median 862 sq ft, median declared valuation $90,000 ⁵.
• Conversions of existing space: 48 permits, median 419 sq ft where the size is listed, median declared valuation $37,500 ⁵.

An attached unit is also capped by the house it attaches to. Under the city's ordinance, an attached ADU is limited to 50% of the existing house, though one under 850 sq ft (under 1,000 sq ft with more than one bedroom) may exceed that cap ⁸. With the median Granada Hills house at 1,786 sq ft ⁴, half of it is about 893 sq ft. If you are weighing a garage conversion, check first that the garage was permitted: how to check a garage's permit.

What extra does the fire zone cost me in Granada Hills?

Mostly it changes materials, upkeep and access, and the materials may not cost much more on a new building. About 16% of Granada Hills single-family parcels touch the city's Very High Fire Hazard Severity Zone map; the rules themselves are covered in building an ADU in the Granada Hills fire zone ¹⁴.

1. Fire-resistant materials. LADBS plan check tells applicants in the zone to comply with the materials and construction methods of Chapter 7A ¹⁰. A 2018 Headwaters Economics study, which priced a 2,500 sq ft house in southwest Montana using national cost data, found that overall wildfire-resistant construction cost 2% less than typical construction, while the roof, vents, soffits and gutters cost $5,860 (27%) more ¹¹. It is not a Los Angeles ADU price, but it suggests the materials premium on new construction is modest.
2. Brush clearance. In the zone, the Fire Department requires year-round clearance of brush and hazardous vegetation within 200 feet of any structure ¹². Keeping it clear is an ongoing cost.
3. Fire Department access. For new construction valued at $50,000 or more, if any part of the building is more than 150 feet from an improved street or approved fire lane, you need clearance from the Fire Department's Hydrants and Access Unit ¹³. On a deep lot, that can decide where the backyard house goes.

Fire-zone permits are a small share of what gets built here. Of the 104 new ADU permits in 91344 since January 2025, 8 sit inside the city's fire-zone map, with a median of 799 sq ft ¹⁴. That is too few to put a dollar figure on the zone.

What do plans, permits and utilities add?

Plans and permit processing run from a fixed $7,490 to $12,990 with one plan company to $20,000 to $30,000 with a full-service design-build firm ¹³. For the rest of the soft costs, see the soft costs of an ADU in Los Angeles.

The utility lines depend on the lot more than the building:

• Water. If a new 1-inch water service is required or chosen, LADWP charges $7,407 for the service and meter in fiscal year 2026/2027 ¹⁵. When it is required is covered in the LADWP water meter guide.
• Electrical panel. One Los Angeles electrical contractor puts a DWP panel upgrade at $3,500 to $7,500 ¹⁶. See do I need a 200 amp panel.
• Sewer. A backyard house at the back of a deep lot needs a long run to the street; see what if the sewer main is far away.
• Soils report. A Glendale geotechnical firm says that in the City of Los Angeles a soils report is typically required only on hillside lots with a slope, and that a modified report averages about $1,500 ¹⁷. That matters more in the foothill part of Granada Hills than on the flat streets.
• Trees. On bigger lots, a protected oak or walnut can shape the plan: protected trees in Granada Hills.

What does an all-in budget look like for a Granada Hills backyard house?

Adding only the sourced lines, a 1,000 sq ft one-story comes to about $338,000 to $396,000, and a 1,200 sq ft two-story to about $398,000 to $466,000. Both are before LADBS plan check and permit fees, impact fees and school fees.

1. Construction: $325,000 to $350,000 for 1,000 sq ft, or $385,000 to $420,000 for 1,200 sq ft, on one contractor's estimates ¹.
2. Plans, engineering and permit processing: $12,990 for that plan company's fixed fee, up to $30,000 with a full-service firm ¹³.
3. A new 1-inch water service, only if required or chosen: $7,407 ¹⁵.
4. A panel upgrade, only if the load calculation calls for it: $3,500 to $7,500 ¹⁶.
5. A modified soils report, only if one is required: about $1,500 ¹⁷.
6. Fire zone, if your lot is in it: Chapter 7A materials, year-round brush clearance and possibly a Fire Department access review ¹⁰¹²¹³.

The low end assumes your lot needs none of items 3 to 5; the high end assumes it needs all three. An 800 sq ft unit on the same math runs about $284,000 to $341,000 ^13151617. Which of these lines your own lot triggers 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 2026-10-09
2. ADU guide: Los Angeles, Abodu (factory-built ADU seller). Facts checked 2026-10-09
3. Los Angeles ADU process: consultation, design, build, permit, Modative / Mod EV (Los Angeles design-build firm). Facts checked 2026-10-09
4. Lot and house sizes of single-family parcels in ZIP 91344 (Greenlight analysis of the County Assessor parcel layer), Los Angeles County Office of the Assessor (data); Greenlight (method). Facts checked 2026-10-09
5. ADU building permits issued in ZIP 91344 (Greenlight analysis of LADBS permit data), LADBS via City of Los Angeles Open Data (data); Greenlight (method). Facts checked 2026-10-09
6. ZA Memorandum No. 143, Revision 1 (LAMC Chapter 1), issued Aug. 1, 2025, Table 1 (detached ADUs), Ordinance ADU column, Los Angeles City Planning / LADBS. Facts checked 2026-10-09
7. 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 2026-10-09
8. ZA Memorandum No. 143, Revision 1 (LAMC Chapter 1), issued Aug. 1, 2025, Table 2 (attached ADUs), Ordinance ADU column and note 16, Los Angeles City Planning / LADBS. Facts checked 2026-10-09
9. 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 2026-10-09
10. Accessory Dwelling Unit Plan Check Correction Sheet (PC/STR/Corr.Lst.20A1, Rev. 8/03/2021), item C.1, Los Angeles Department of Building and Safety (LADBS). Facts checked 2026-10-09
11. Building a Wildfire-Resistant Home: Codes and Costs (Nov. 26, 2018), Headwaters Economics (with IBHS and Bechtle Architects). Facts checked 2026-10-09
12. Brush clearance requirements, Los Angeles Fire Department (LAFD). Facts checked 2026-10-09
13. Accessory Dwelling Unit Plan Check Correction Sheet (PC/STR/Corr.Lst.20A1, Rev. 8/03/2021), item B.7, Los Angeles Department of Building and Safety (LADBS). Facts checked 2026-10-09
14. Fire-zone share of Granada Hills parcels and new ADU permits (Greenlight analysis: City of LA Very High Fire Hazard Severity Zones layer), City of Los Angeles GeoHub; LA County Assessor; LADBS Open Data (Greenlight analysis). Facts checked 2026-10-09
15. Schedule of Charges for Water Facilities, Fiscal Year 2026/2027 (Rev. 6/26), Los Angeles Department of Water and Power. Facts checked 2026-10-09
16. DWP electrical panel upgrade, LA Pro Electrical (one contractor's published range). Facts checked 2026-10-09
17. ADU and garage conversions: geotechnical soil report, Applied Earth Sciences (Glendale geotechnical firm). 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.