Everything homeowners need to know about building an accessory dwelling unit in Hayward - size limits, setbacks, permits, and how the city's ADU rules line up with California's statewide ADU law.
Last verified: August 2026
7/10 · ADU-friendly
1,200 sq ft*
Max ADU size
16 ft*
Max height
Not required
Owner-occupancy
By-right
Permit type
This page summarizes Hayward Municipal Code Section 10-1.2740 (Accessory Dwelling Units) and California's statewide ADU law (Government Code Sections 66310-66342) for general reference - it is not legal advice. The state has flagged Hayward's ADU ordinance filing as outdated (see ordinance history below). Always confirm current requirements with the Hayward Planning Division before designing or applying for permits. See sources below.
Zoning & size requirements
What you're allowed to build
ADU type
Max size
Max height
Notes
Detached (new construction)
1,200 sq ft, or 50% of the primary dwelling's habitable floor area, whichever is less
16 ft, measured to the midpoint of the highest gable on a pitched roof (a ridge can run higher)
4 ft side and rear setbacks; a 6 ft separation from other structures is required
Attached (addition)
Same 1,200 sq ft / 50% cap as detached units
Up to 25 ft, generally following the underlying zoning district's height limit
Front setback follows the underlying zone
Converted ADU (garage, existing structure)
No separate cap if floor area isn't increased
Not separately height-limited
No setbacks required for conversions of a legally established existing structure
Junior ADU (JADU)
500 sq ft, within existing walls of the primary home
Within existing primary structure
Owner-occupancy required unless the JADU has its own bathroom, per state law
Allowed zoning districts
Any district where residential use is permitted, citywide, under Hayward Municipal Code Section 10-1.2740. State law guarantees at least an 800 sq ft, 16 ft tall ADU regardless of any stricter local limit. Confirm your parcel's zoning with the Hayward Planning Division.
Additional standards
Setbacks, parking & other rules
Setbacks
4 ft minimum from side and rear property lines for new construction; no setback required for conversions of an existing legal structure; front setback follows the underlying zoning district
Parking
Up to 1 space per bedroom may be required, but it's waived within a half mile of public transit and for any conversion ADU; no replacement parking is required when a garage is converted
Units per lot
1 ADU + 1 JADU on a single-family lot. A lot with an existing multifamily building can add up to 8 detached ADUs (not exceeding the existing unit count) plus interior conversions of up to 25% of existing units
Owner-occupancy
Not required for a standard ADU, under statewide AB 976 (effective January 1, 2024). A JADU still requires owner-occupancy unless it has its own bathroom
Building code
Must meet the California Residential Code as locally amended; Hayward's all-electric new-construction (Reach Code) standards can apply to new detached ADUs, so confirm current thresholds with the Building Division
Rental rules
No separate city rental license is required specifically for an ADU; standard California landlord-tenant law applies
Ordinance history
How Hayward's ADU rules got here
2017Statewide by-right ADU law takes effect, and Hayward adopts its ordinance. California Government Code Section 65852.2 begins requiring cities, including Hayward, to approve most ADUs ministerially; Hayward's ADU ordinance on file with the state dates to this year.
2020-2024Years of statewide ADU law changes. A wave of state bills (including AB 68, AB 881, AB 587, AB 2299, AB 671 in 2020, and AB 976 and SB 1211 in 2024) repeatedly expanded ADU rights, eliminating owner-occupancy requirements and allowing up to 8 detached ADUs on qualifying multifamily lots.
Jan 2025Local zoning ordinance updated. Hayward's zoning code was amended under Ordinance 25-02, adopted January 21, 2025, updating Chapter 10 provisions including the ADU standards at Section 10-1.2740.
Oct 2025HCD flags an outdated ordinance filing. A Letter of Technical Assistance from the California Department of Housing and Community Development, dated October 8, 2025, noted that the most recent ADU ordinance HCD had on file for Hayward dated to 2017 and may be out of compliance with current state law, and asked the city to either confirm continued compliance or submit an updated ordinance by November 7, 2025.
Worth knowing: Hayward's local zoning code appears to already reflect many of the more recent statewide changes, including the elimination of owner-occupancy requirements and the 8-unit multifamily allowance. The HCD letter is a reminder that ADU law changes quickly and cities don't always keep their state filings current - always confirm the standards in effect with the Planning Division rather than relying solely on this page or any other secondary source.
Permit process
How Hayward ADU permitting works
1
Pre-application check
Confirm your zoning and lot capacity with a City planner at planning.division@hayward-ca.gov or (510) 583-4216 before you design.
2
Consider a pre-approved plan
Hayward's ADU Plans Gallery lists designers offering plans already pre-approved by the city, which can shorten plan review compared with a fully custom design.
3
Prepare your submittal
You'll need a site plan, floor plans and elevations for the ADU, and existing floor plans of the primary home to verify the size-limit calculation.
4
Register and submit through the e-Permit Portal
All ADU and JADU applications go through Hayward's online e-Permit Portal; pay the plan review fee before review begins.
5
Administrative review
Applications are reviewed administratively with no public hearing. State law requires a decision within 60 days of a complete application; an application not acted on in time is automatically approved.
6
Building permit & inspections
Once your building permit is issued, schedule the standard framing, plumbing, electrical, and final inspections as construction proceeds.
Fees and timelines are approximate - confirm current figures with the Hayward Planning Division or e-permits@hayward-ca.gov.
Budgeting
What it costs to build an ADU in Hayward
Garage conversion
Roughly $70,000-$180,000, the least expensive path since the shell already exists
Basement conversion
Uncommon in Hayward's largely slab-built housing stock; where feasible, costs run comparable to or higher than a garage conversion
New detached ADU
Roughly $150,000-$340,000+ for a code-compliant, freestanding unit; Bay Area labor and material costs tend to run toward the higher end of this range
Permit & plan review fees
Reported at roughly $5,000-$12,000 total for plan check and building permit fees on a typical detached ADU, plus separate utility connection costs; impact fees are waived under 750 sq ft
Pre-approved plans
Using a plan from Hayward's ADU Plans Gallery can reduce design costs and plan-review time versus a fully custom design
These are general ranges from local contractor estimates and regional reporting, not quotes - actual cost depends heavily on lot conditions, finishes, and utility connection needs. Ask any contractor bidding your project for a fee estimate that separates plan review, building permit, and utility connection costs, since they're often billed separately.
Before you apply
Tips for a smooth approval
Browse the ADU Plans Gallery before hiring a designer. Building from an already pre-approved plan can meaningfully cut your design timeline and plan-review cost.
Confirm your zoning district before you design. A quick pre-application check with the Planning Division avoids redesigning a project that doesn't fit your lot.
Ask about all-electric construction requirements early. Hayward's Reach Code standards can affect appliance and system choices for a new detached ADU, and it's easier to design around them from the start than to retrofit later.
Keep new construction at or under 750 sq ft if avoiding impact fees matters to you. Larger units can be charged impact fees proportional to the primary dwelling's floor area.
Don't assume a secondary source has the final word. With HCD flagging Hayward's ordinance filing as potentially outdated, verify current standards directly with the Planning Division before finalizing your design.
FAQ
Common questions
Do I need to live on the property to build an ADU in Hayward?
No. California's AB 976 permanently eliminated owner-occupancy requirements for standard ADUs statewide as of January 1, 2024. A JADU still requires owner-occupancy unless it has its own bathroom.
How many ADUs can I build on one lot in Hayward?
A single-family lot can add 1 ADU plus 1 JADU. A lot with an existing multifamily building can add up to 8 detached ADUs (not exceeding the number of existing units) plus interior conversions of up to 25% of existing units.
Do I need extra parking for an ADU?
Up to 1 space per bedroom can be required, but it's waived within a half mile of public transit and for any conversion ADU. No replacement parking is required when a garage is converted.
How long does the permit process take?
Applications are reviewed administratively with no public hearing. State law requires a decision within 60 days of a complete application, and an application not acted on in time is automatically approved.
What's the maximum size for a detached ADU in Hayward?
Up to 1,200 sq ft, or 50% of the primary dwelling's habitable floor area, whichever is less, with a 16 ft height limit. State law guarantees at least an 800 sq ft, 16 ft tall ADU regardless of any stricter local limit.
How much does an ADU cost to build in Hayward?
Garage conversions tend to run roughly $70,000-$180,000, and new detached units roughly $150,000-$340,000 or more, based on local contractor estimates and regional reporting. Permit and plan review fees are reported at roughly $5,000-$12,000 for a typical detached ADU, not counting utility connections.
What is the ADU Plans Gallery?
It's Hayward's directory of designers offering ADU plans that have already been pre-approved by the city. Building from one of these plans can save on design costs and shorten plan review compared with a fully custom submittal.
Is Hayward's ADU ordinance fully compliant with state law?
There's an open question. A California HCD Letter of Technical Assistance dated October 8, 2025 noted that the most recent ADU ordinance HCD had on file for Hayward was from 2017 and may be outdated, and asked the city to confirm compliance or submit an updated ordinance. Hayward's local zoning code appears to already reflect many recent state changes, but confirm current status with the Planning Division.
Can I add multiple ADUs if I own a multifamily property in Hayward?
Yes. Under statewide SB 1211 (2024), owners of an existing multifamily property can add up to 8 detached ADUs on one lot, plus interior conversions of up to 25% of existing units, subject to Hayward's standards.
