Can I build an ADU in Sylmar (91342)?

Can I build an ADU on my Sylmar lot?

Almost certainly some kind of ADU, yes. Los Angeles allows ADUs in any zone where a house is a permitted use, and that covers the RS, R1, RA and RE zones that make up most of Sylmar's single-family lots ⁶⁵.

State law guarantees three kinds of ADU that the city has to approve on a single-family lot:

• A detached backyard house of up to 800 square feet, with four-foot side and rear setbacks, which can be paired with a JADU ⁷.
• A garage conversion or conversion of another existing accessory building, which can grow by up to 150 square feet only to fit an entry or exit ⁸.
• A junior ADU (JADU) of no more than 500 square feet, inside the house ⁹.

On top of that, the city's own ADU ordinance allows a larger detached unit of up to 1,200 square feet and two stories ¹⁰. That bigger option is where Sylmar's overlays start to matter. If you are weighing a JADU against a full unit, our JADU vs ADU guide covers the difference.

How big are Sylmar lots, and what fits on mine?

Bigger than the flat-Valley average. Of the 12,808 single-family parcels in ZIP 91342 inside the City of Los Angeles, the middle lot is 7,630 square feet, a quarter are under 6,885 square feet, and a quarter are over 10,613 square feet ².

That matters in two ways. On a typical Sylmar lot there is usually room for an 800-square-foot backyard house with four-foot setbacks, with space left for the driveway and yard; our guide to what fits on a 6,600 sq ft lot walks through the layout on a smaller tract lot. On the larger quarter of lots, the 1,200-square-foot Ordinance ADU becomes realistic ¹⁰.

The Valley's RA, RE and RS zones also carry a residential floor area (RFA) limit for the whole lot. City Planning says that limit cannot be enforced on a state-law ADU, and it cannot be used to shrink a detached ADU below 800 square feet ¹¹. It can still limit a bigger Ordinance ADU, so on a large lot that already has a large house, check the floor area math before you design 1,200 square feet.

Is my Sylmar lot in a fire zone or a Hillside Area?

About one in four Sylmar homes touches the fire zone, and about one in eight is in a Hillside Area. We matched the city's map layers against every single-family parcel in 91342: 3,022 of 12,808 parcels (24%) touch the Very High Fire Hazard Severity Zone, and 1,529 (12%) sit in a Hillside Area ³⁴.

The overlap is the number to watch. The city code bars ADUs on lots in both a Very High Fire Hazard Severity Zone and a Hillside Area, but City Planning says that bar may not be enforced on state-law ADUs ¹². So the overlap mostly limits the larger Ordinance ADU. By our count, 911 Sylmar single-family parcels, about 7%, fall in both zones ⁴.

Treat the fire-zone count as a floor. The city layer we used was last edited in 2019, and CAL FIRE issued new recommended fire hazard maps for Los Angeles on March 24, 2025, which the Fire Department said would affect more parcels ³¹³. For what a fire zone changes in the build itself, read our fire zone guide; for slope, street width and grading, read the Hillside Area guide.

I keep horses, or my neighbor does. Does that stop an ADU?

No, but it is the question most Sylmar guides skip. City Planning says ADUs and JADUs are exempt from the city's distance rules between horse enclosures and homes, because state law does not allow those rules to be applied to them ¹⁶.

Sylmar is one of the few places where this comes up. City Planning lists Sylmar among the Valley neighborhoods where nearly all of the city's "K" Equinekeeping Districts are found ¹⁴. By our count, 1,672 of Sylmar's 12,808 single-family parcels, about 13%, sit in a K district, most of them zoned RA-1-K ⁵.

The distance rules still bind the horse side of the fence. In a K district, an equine enclosure can never be closer than 35 feet to the habitable rooms of any dwelling unit; outside a K district, a horse structure has to stay 75 feet from a neighbor's habitable rooms ¹⁵. So:

• If your neighbor keeps horses, your ADU can be built at the normal four-foot setback. City Planning reports that this can make the neighbor's existing, legal enclosure nonconforming and in some cases lead to enforcement against them ¹⁷. It is worth a conversation before your plans are drawn.
• If you keep horses yourself, place the ADU with your own corral in mind, because the 35-foot rule is written around the enclosure, not the ADU ¹⁵.

This is changing. In a June 24, 2026 report, City Planning recommended that the city prepare an ordinance to reconcile the housing and horsekeeping rules ¹⁸. As of October 2026 we have not found an adopted ordinance, so check the latest before you rely on either version.

Are other Sylmar homeowners actually getting ADU permits?

Yes, steadily. LADBS issued 114 ADU and JADU building permits in 91342 in 2023, 108 in 2024, 120 in 2025 and 104 in 2026 through Oct. 4, which puts 2026 on pace to beat 2025 ¹. Counts are permits, not units, because one project can carry more than one permit.

Sylmar builds at a slower rate per home than its flatter neighbors. In 2025 the city issued about 9 ADU permits for every 1,000 single-family parcels in 91342, compared with about 12 in Pacoima 91331, 16 in Granada Hills 91344 and 23 in Reseda 91335 ¹². The overlays above are a likely part of the reason, though the permit data does not say why. Our Valley permits by ZIP guide has the full ranking.

What should I look up first for my Sylmar address?

Start with the city's free parcel report. Look up your address in ZIMAS, the city's mapping system for a parcel's zoning and permit history ¹⁹, and write down these items:

1. The full zone string. A zone such as RA-1-K tells you both the base zone and whether you are in a K horsekeeping district ⁵.
2. The fire zone and Hillside Area rows. Both together limit the Ordinance ADU; either one changes how you build ¹².
3. Lot size. Compare it with the Sylmar range above to see whether a 1,200-square-foot unit is even worth sketching ².
4. The garage's permit history, if you want a conversion. Our guide to checking whether a garage was permitted shows how.

Then look at the things ZIMAS does not settle: how far the sewer main is from your lot (sewer guide), whether a deep backyard house is more than 150 feet from the street for fire access (access guide), and whether your soil or slope calls for a soils report. Putting those answers together for one address is the kind of thing a lot check settles.

Quick answers

Sources

1. Building Permits Issued from 2020 to Present (N), dataset pi9x-tg5x, ZIP 91342 and comparison ZIPs, LADBS via City of Los Angeles Open Data (Greenlight query). Facts checked 2026-10-11
2. LA County Assessor parcel layer (LACounty_Parcel), single-family parcels in ZIP 91342, City of Los Angeles, LA County Assessor (Greenlight analysis). Facts checked 2026-10-11
3. Greenlight parcel count: LA County Assessor parcels (City of LA single-family, ZIP 91342) intersected with the City of LA Very High Fire Hazard Severity Zones layer, LA County Assessor parcel layer / City of Los Angeles GeoHub (Greenlight analysis). Facts checked 2026-10-11
4. Greenlight parcel count: City of LA single-family parcels in ZIP 91342 tested against the Hillside Area and Very High Fire Hazard Severity Zone layers, LA County Assessor parcel layer / City of Los Angeles GeoHub (Greenlight analysis). Facts checked 2026-10-11
5. Greenlight parcel count: City of LA single-family parcels in ZIP 91342 by zone, from the City Planning zoning layer, LA County Assessor parcel layer / City of Los Angeles GeoHub, City Planning zoning (Greenlight analysis). Facts checked 2026-10-11
6. ZA Memorandum No. 143, Revision 1 (LAMC Chapter 1): Implementation of the ADU Ordinance and State ADU Law, issued Aug. 1, 2025, Q.2, Los Angeles City Planning / LADBS. Facts checked 2026-10-11
7. ZA Memorandum No. 143, Revision 1 (LAMC Chapter 1): Implementation of the ADU Ordinance and State ADU Law, issued Aug. 1, 2025, quoting Gov. Code § 66323(a)(2), Los Angeles City Planning / LADBS. Facts checked 2026-10-11
8. ZA Memorandum No. 143, Revision 1 (LAMC Chapter 1): Implementation of the ADU Ordinance and State ADU Law, issued Aug. 1, 2025, on Gov. Code § 66323(a)(1), Los Angeles City Planning / LADBS. Facts checked 2026-10-11
9. ZA Memorandum No. 143, Revision 1 (LAMC Chapter 1): Implementation of the ADU Ordinance and State ADU Law, issued Aug. 1, 2025, section B (JADUs), Los Angeles City Planning / LADBS. Facts checked 2026-10-11
10. ZA Memorandum No. 143, Revision 1 (LAMC Chapter 1): Implementation of the ADU Ordinance and State ADU Law, issued Aug. 1, 2025, Table 1 (detached ADUs), Ordinance ADU column, Los Angeles City Planning / LADBS. Facts checked 2026-10-11
11. ZA Memorandum No. 143, Revision 1 (LAMC Chapter 1): Implementation of the ADU Ordinance and State ADU Law, issued Aug. 1, 2025, Q.3, Los Angeles City Planning / LADBS. Facts checked 2026-10-11
12. ZA Memorandum No. 143, Revision 1 (LAMC Chapter 1): Implementation of the ADU Ordinance and State ADU Law, issued Aug. 1, 2025, Q.42, Los Angeles City Planning / LADBS. Facts checked 2026-10-11
13. 2025 CAL FIRE Fire Hazard Severity Zones Map Recommendation (Apr. 4, 2025), Los Angeles Fire Department. Facts checked 2026-10-11
14. Report back on recommendations relative to equestrian uses, CF 16-1468-S4 and CF 25-0096, June 24, 2026, Los Angeles City Planning. Facts checked 2026-10-11
15. Report back on recommendations relative to equestrian uses, CF 16-1468-S4 and CF 25-0096, June 24, 2026, on LAMC 12.21 C.5(a) and 13.05, Los Angeles City Planning. Facts checked 2026-10-11
16. Report back on recommendations relative to equestrian uses, CF 16-1468-S4 and CF 25-0096, June 24, 2026, Impacts on Equine Distancing Requirements, Los Angeles City Planning. Facts checked 2026-10-11
17. Report back on recommendations relative to equestrian uses, CF 16-1468-S4 and CF 25-0096, June 24, 2026, Impacts on Equine Distancing Requirements, Los Angeles City Planning. Facts checked 2026-10-11
18. Report back on recommendations relative to equestrian uses, CF 16-1468-S4 and CF 25-0096, June 24, 2026, recommendation 1, Los Angeles City Planning. Facts checked 2026-10-11
19. Zoning Search (ZIMAS), Los Angeles City Planning. 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.