Can you build an ADU in Northridge?

How big are Northridge lots compared with the rest of the Valley?

Bigger than most. We counted every City of Los Angeles single-family parcel in both Northridge ZIP codes on the LA County Assessor's parcel map ¹.

• 91324: 4,761 parcels with a median lot of 8,160 sq ft. About 35 percent are 10,000 sq ft or larger, and 20 percent are 15,000 sq ft or larger.
• 91325: 5,473 parcels with a median lot of 11,705 sq ft. About 66 percent are 10,000 sq ft or larger, 39 percent are 15,000 sq ft or larger, and 10 percent pass 20,000 sq ft.

For comparison, the median lot in Reseda 91335 is 6,639 sq ft ¹, close to the lot in our guide to what fits on a 6,600 sq ft lot. An 800 sq ft backyard house covers about 7 percent of a median 91325 lot.

The houses date mostly from the postwar build-out. The median main house was built in 1960 in 91324 and in 1956 in 91325, and the median house is 1,870 sq ft in 91324 and 2,153 sq ft in 91325 ¹. On a house that age, ask early about the sewer line and the electrical panel, because those tend to move an ADU budget more than yard space does.

What size ADU can I build on a big Northridge lot?

You can always build 800 sq ft, and you may be able to build up to 1,200 sq ft. Start by looking up your zone on ZIMAS, the City Planning map that shows a parcel's zoning and its permit history ³. Los Angeles then gives you two tracks.

• State ADU. One detached new unit of up to 800 sq ft, 4 feet from the side and rear lines, is allowed on a lot with a single-family house ². The city's floor-area limit cannot be enforced against it ⁵.
• Ordinance ADU. Under the city's own ordinance, a detached unit can reach 1,200 sq ft and two stories ⁴. It is still subject to zoning limits such as the lot's floor area (RFA in the R1, RE, RS and RA zones), front yard setbacks and lot coverage, which can make it smaller ⁵.

A big lot is where the Ordinance ADU becomes worth a look. Whether the larger unit fits depends on how much of those limits your existing house already uses, so have the numbers run before anyone designs to 1,200 sq ft. Our guide to ADU height limits covers how tall each type can be.

Can I build more than one unit on my Northridge lot?

Yes, up to three on a lot with one house, if you pick a combination the city allows. The city's ADU memo says a detached State ADU can be combined with an attached Ordinance ADU, or an attached State ADU with a detached Ordinance ADU ⁶. A JADU, a junior unit of no more than 500 sq ft inside the house ⁸, can generally be added to either one ⁷.

So on a single-family lot the menu looks like this:

1. A detached State ADU of up to 800 sq ft, plus an attached Ordinance ADU built into or onto the house, plus a JADU ⁶⁷.
2. A detached Ordinance ADU of up to 1,200 sq ft, plus an attached State ADU inside the house, plus a JADU ⁶⁷.

What the list does not include is two detached backyard houses. State law allows one detached new-construction ADU on a lot with a single-family house ⁹, and the city's combinations pair one detached unit with one attached unit ⁶. For how a JADU differs from a full ADU, see JADU vs ADU.

Does a big lot bring problems a small lot does not?

Yes, and most of them come down to distance. The farther back the unit sits, the more these three items matter.

1. Fire access. For new construction valued at $50,000 or more, the Fire Department's Hydrants and Access Unit must clear the project when any part of the building is 150 feet from an improved street or approved fire lane ¹⁰. On a deep lot, a backyard house in the far corner can cross that line. Our guide to the 150-foot rule explains how it is measured.
2. Sewer and utility runs. A unit at the back of a long yard needs longer sewer, water and power lines. You are responsible for keeping your house lateral working from its connection at the main up to your property line ¹¹, and city staff use NavigateLA to confirm where the public sewer is ¹². If the main is far from your lot, read our guide on a sewer main over 200 feet away.
3. Lot history. LADBS checks when your lot was created. Lots divided after June 1, 1946 must meet the zone's lot area and width rules, and lots divided after July 29, 1962 need a Certificate of Compliance from City Planning ¹³.

If there is a large native tree in the yard, also read our guide to protected trees before you pick a spot.

Are Northridge homeowners building ADUs, and is it growing?

Yes, though the two ZIP codes are moving in opposite directions this year. Here are the ADU and JADU building permits LADBS issued ¹⁴:

• 91324: 43 in 2023, 45 in 2024, 46 in 2025, and 53 from January 1 through October 3, 2026, already more than all of 2025. That is on pace for about 70, roughly 52 percent above last year.
• 91325: 81 in 2023, 79 in 2024, 103 in 2025, and 60 so far in 2026. That is on pace for about 79, roughly 23 percent below last year's high.

Together the two ZIPs are on pace for about 149 permits in 2026, level with the 149 issued in 2025 ¹⁴. Over a longer stretch the growth is clear: the two combined went from 61 permits in 2020 to 114 in 2022 and 149 in 2025 ¹⁴. Numbers this small can swing on a few projects, so read one year's change as a hint. Our guide to Valley ADU permits by ZIP ranks Northridge against the rest.

The big lots have not tilted the work toward new buildings. Of the 262 permits issued in both ZIPs since January 2025, 139 were alterations to an existing building, 81 were new buildings and 42 were additions ¹⁴. New buildings were about 31 percent, the same share as in Pacoima, where lots are much smaller ¹⁴. These counts are permits, not homes, since one project can carry more than one permit.

Is Northridge in a fire zone or a Hillside Area?

Very little of it, on the map we checked. On the city's Very High Fire Hazard Severity Zone layer, no single-family parcel in 91324 and one parcel in 91325 touches the zone ¹. That layer was last edited in 2019, so confirm your own parcel on ZIMAS ³.

If your lot does turn out to be in the fire zone, a State ADU of up to 800 sq ft is still allowed; our fire zone guide explains what changes. The same goes for a Hillside Area, covered in our Hillside Area guide.

What should I check first on my own lot?

Work from the cheapest answer to the most expensive one.

1. ZIMAS: your zone, any overlays, and the permit history of the house and any garage ³.
2. Lot history: when the lot was created, and whether it needs a Certificate of Compliance ¹³.
3. Placement: how far the spot you have in mind is from the street, measured against the 150-foot line ¹⁰.
4. Sewer: where the public main is and how far your line runs to it ¹¹¹².
5. Floor area: how much of the lot's RFA your house already uses, if you want the larger Ordinance ADU ⁵.

This is the kind of thing a lot check settles in one pass, before you pay for plans.

Quick answers

Sources

1. LA County Assessor parcel layer (LACounty_Parcel), City of Los Angeles single-family parcels in ZIPs 91324 and 91325 (with 91335 for comparison); with LA City GeoHub Very High Fire Hazard Severity Zones layer, LA County Assessor / City of Los Angeles GeoHub (Greenlight analysis). Facts checked 2026-10-11
2. Accessory Dwelling Unit Handbook (March 2026), 66323 Units: Single-Family Detached ADUs, California Department of Housing and Community Development (HCD). Facts checked 2026-10-11
3. Zoning Search (ZIMAS), Los Angeles City Planning. Facts checked 2026-10-11
4. ZA Memo No. 143 Revision 1, Table 1: Detached ADU options (Ordinance ADU vs State ADU), Los Angeles City Planning, Office of Zoning Administration. Facts checked 2026-10-11
5. ZA Memo No. 143 Revision 1, Q.3: How square footage is calculated, Los Angeles City Planning, Office of Zoning Administration. Facts checked 2026-10-11
6. ZA Memo No. 143 Revision 1, I.A Combinations of ADUs and JADUs, Los Angeles City Planning, Office of Zoning Administration. Facts checked 2026-10-11
7. ZA Memo No. 143 Revision 1, I.A Combinations of ADUs and JADUs (JADUs), Los Angeles City Planning, Office of Zoning Administration. Facts checked 2026-10-11
8. Accessory Dwelling Unit Handbook (March 2026), What is a JADU?, California Department of Housing and Community Development (HCD). Facts checked 2026-10-11
9. ZA Memo No. 143 Revision 1, II.A ADUs and JADUs Required to be Approved by State Law, Los Angeles City Planning, Office of Zoning Administration. Facts checked 2026-10-11
10. Accessory Dwelling Unit Plan Check Correction Sheet, item B.7, Los Angeles Department of Building and Safety (LADBS). Facts checked 2026-10-11
11. Sewer (S) Permits: Maintenance of the HC Lateral, City of Los Angeles Bureau of Engineering (BOE) Permit Manual. Facts checked 2026-10-11
12. Sewer (S) Permits: S-Permit Processing Procedures, City of Los Angeles Bureau of Engineering (BOE) Permit Manual. Facts checked 2026-10-11
13. Accessory Dwelling Unit Plan Check Correction Sheet, item B.2, Los Angeles Department of Building and Safety (LADBS). Facts checked 2026-10-11
14. Building Permits Issued from 2020 to Present (N), dataset pi9x-tg5x, ZIPs 91324 and 91325 (with 91331 for comparison), LADBS via City of Los Angeles Open Data (Greenlight query). Facts checked 2026-10-11
15. Accessory Dwelling Unit Handbook (March 2026), Lot size, California Department of Housing and Community Development (HCD). Facts checked 2026-10-11
16. Accessory Dwelling Unit Handbook (March 2026), Setbacks, California Department of Housing and Community Development (HCD). Facts checked 2026-10-11
17. ZA Memo No. 143 Revision 1, ADUs with SB 9 (2021), Los Angeles City Planning, Office of Zoning Administration. Facts checked 2026-10-11
18. Accessory Dwelling Unit Handbook (March 2026), Summary of Recent Changes, California Department of Housing and Community Development (HCD). Facts checked 2026-10-11

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.