ADU Builder in Hayward, CA
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Hayward ADU Rules
- Detached ADU: up to 1,200 sq ft, 16 feet tall (18 within half a mile of transit).
- Attached ADU: up to 50% of the main home; conversions have no size cap.
- JADU: up to 500 sq ft.
- Setbacks: 4 feet side and rear, 5 feet from other structures.
- Attached ADUs need a one-hour fire separation, and PG&E may require a separate meter.
- School and park fees apply to ADUs of 750 sq ft or more.
Hayward also has a pre-approved detached ADU plan program. The state reviewed Hayward’s ADU ordinance in 2025, so we confirm current standards for each lot.
ADU Construction
Fire and Sprinklers
An ADU needs sprinklers if the main house has them, if a detached ADU is over 1,200 sq ft, or if an attached ADU is over 50% of the house or the combined area exceeds 3,600 sq ft.
Hayward Fault: the fault runs within a few hundred feet of Mission Boulevard. New construction in fault, liquefaction or landslide zones needs a licensed geotechnical engineer’s investigation, and occupied buildings cannot sit over an active fault, with a 50-foot setback unless the engineer recommends otherwise.
City Hall, 777 B Street, 1st floor lobby, Hayward, CA 94541
Building (510) 583-4140, e-*******@********ca.gov · Planning (510) 583-4216
Monday to Thursday, 9 a.m. to 1 p.m. walk-in or virtual; 1 to 5 p.m. by appointment; Friday virtual appointments only. All permits go through the e-Permits Portal (no paper), where inspections are also scheduled and tracked. Construction hours: 7 a.m. to 7 p.m. Monday to Saturday, 10 a.m. to 6 p.m. Sundays and holidays.
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Other Hayward services: Bathrooms · Kitchens · Additions · New Homes · Hayward overview
Same service nearby: Castro Valley · Union City · Fremont
See how to build an ADU.
Hayward ADU Builder FAQ
How large can a detached ADU be in Hayward?
Up to 1,200 sq ft.
Are there pre-approved ADU plans?
Yes, a pre-approved detached ADU program.
When does an ADU need sprinklers?
If the house has them, a detached ADU exceeds 1,200 sq ft, or combined area exceeds 3,600 sq ft.
Is a separate meter required?
PG&E may require one.
New for 2027: Two Detached ADUs in Hayward (AB 956)
AB 956 lets Hayward homeowners build two detached ADUs from January 1, 2027. See Hayward’s ADU checklist rules, the HCD review and state standards.
Read the full guide: Two Detached ADUs in Hayward | AB 956 overview for every city we serve