What are the Hawthorne ADU rules in 2026?
Ike Mbelu, Principal Partner · Last checked
On this page: The short answer · What Hawthorne's code sets · What state law guarantees
The short answer
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Ch. 17.24b
Three units, no hearing
Hawthorne, in LA County, allows one attached ADU, one detached ADU and one junior ADU on a single-family lot, reviewed by the Planning Director without notice or a hearing. A new detached ADU can reach 1,000 square feet at 16 feet and one story, or 20 feet and two stories near major transit. Hawthorne Municipal Code Ch. 17.24b.
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What Hawthorne's code sets
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01
A new chapter, July 2026
Adopted by Ordinance 2265 on July 14, 2026, with preapproved ADU plans. A guide that doesn't cite Chapter 17.24b predates it. §17.24b.010, .030.
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02
Size and height
Detached: 1,000 square feet. Attached: half the house but at least 800, so a 1,400 square foot house still gets 800, not 700. Junior ADU: 500. Attached height follows the house, up to 25 feet. §17.24b.050.
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03
Setbacks and conversions
New ADU: four feet at side and rear. A garage converted in place needs none and may add 150 square feet for an entry. An ADU of at least 800 square feet may exceed the zone's lot coverage. §17.24b.050.
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04
Parking
One space, waived within half a mile of public transit or for a garage or in-house conversion. Tandem on the driveway counts. §17.24b.050.
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05
Apartment lots
Existing building: convert unused space into ADUs, at least one and up to 25 percent of the units, plus up to eight detached, capped at the existing unit count. Proposed building: two detached. §17.24b.040.
What state law guarantees
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01
The size window
Cities can't cap an ADU below 850 square feet, or 1,000 with two or more bedrooms, and detached ADUs top out at 1,200. Hawthorne's 1,000 fits. Gov. Code §66321(b)(2), §66314(d)(5).
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02
Setback and parking ceilings
No city can require more than four feet at the side and rear, or more than one space per ADU or per bedroom. §66314(d)(7), (d)(10).
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03
Stacking with SB 9
An unsplit R-1 lot with two SB 9 homes can still add ADUs. §17.24f.030. See SB 9 in Los Angeles, the LA County ADU rules, and building in Hawthorne.
This is a summary of the Hawthorne Municipal Code and state law, not legal advice. Confirm the current code for your site.
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