Building an ADU in Hayward, California

What you can build in Hayward

Hayward's zoning code doesn't set its own ADU standards. Since Ordinance 24-01 (January 23, 2024), Section 10-1.2741 simply refers to the state ADU and junior ADU laws "as amended from time to time." The city says all projects "are reviewed for compliance with applicable California State Codes and California State Law." The working standards are in the city's checklists, updated April and July 2026.

Single-family lots: the city's checklists say properties "are limited to one (1) Detached/ Attached ADU and one (1) JADU." State law guarantees more. HCD says cities "must allow at least one ADU constructed from existing space, one JADU, and one newly constructed detached ADU" on single-family lots. If you want all three, confirm with the Planning Division.

Multifamily lots: you can convert non-living space such as storage rooms or garages into ADUs, up to 25% of the existing units (at least one). You can also add detached ADUs, up to the number of existing units or eight, whichever is less. On a lot with a proposed multifamily building, the limit is two detached ADUs.

Before applying, the city asks you to contact a planner to confirm your site is eligible. For the statewide rules, see our California ADU guide. [1][2][3][4][5][6]

Size, height and setbacks

From the city's single-family ADU checklist (April 2026):

• Size: a new detached ADU can be up to 1,200 sq ft of interior livable space. A new attached ADU can be up to 50% of the main home's total floor area. For cities without their own compliant ADU ordinance, HCD says the 50% limit for attached ADUs still allows at least 800 sq ft, so ask Planning if your house is small. There are no size limits for converting existing, permitted structures.
• Height: detached ADUs are limited to 16 ft, or 18 ft within a half mile of a major transit stop or high-quality transit corridor. Attached ADUs follow the zone's height limit. Conversions inside existing, permitted structures have no height limit. State law also allows 2 more feet near transit when the ADU's roof pitch matches the main house, so ask Planning if that applies to you.
• Setbacks: 4 ft from side (including street-side) and rear lot lines, the zone's front setback, and 5 ft from other structures. No setbacks are required for conversions of existing, permitted structures.

Detached ADUs are treated as separate homes under the building code, so plans must show fire separation from property lines and other buildings. [3][6]

Building code points the city checks

• No interior door to the house: the city says an ADU needs its own exterior entrance and that "an internal connection between the ADU and the main dwelling is not allowed because of the fire rated wall requirements."
• Fire separation: an attached ADU needs a one-hour fire-rated wall from the bottom of the footing to the underside of the roof deck. For a garage conversion under living space, the floor/ceiling between the units must be rated too.
• Fire sprinklers: required if the main house has them, or if other work on the house would require them.
• Heating and water: the ADU needs its own heat source with no shared return air. Water heating can be separate or a shared system sized for both units.
• Address: every ADU gets its own address.

[3]

Parking

Hayward's ADU checklists don't list any parking requirement for ADUs. Under state law, a city can't require parking for an ADU within a half-mile walk of public transit or for an ADU created inside existing space, and it can't make you replace a garage or carport you convert or tear down to build an ADU. HCD also says a city may not require parking for a JADU, even when it is converted from an attached garage. Confirm with the Planning Division for your lot. [3][6][7]

Fees

A plan review fee is due before review starts; other permit fees are due when the permit is ready to issue. Hayward's Permit Center Fee Estimator lists specific development fees. A 2023 city handout put total ADU fees at "$6,000 to over $25,000," with garage conversions lowest and new detached ADUs highest.

Impact fees: the city's checklist says park impact and school district fees apply to ADUs "equal or greater than 750 square-feet," and affordable housing fees apply at that size if the project adds two or more new units. State law says an ADU of 750 sq ft or less of interior livable space is exempt from impact fees, and larger ADUs can be charged only in proportion to their size compared with the main house. The city's wording includes ADUs of exactly 750 sq ft, so confirm with the Planning Division if yours is that size. School districts may charge fees on ADUs over 500 sq ft.

Water and sewer: the city says connection and capacity charges "apply to all ADUs" and to all JADUs. Its September 2025 utility checklist estimates:

• new construction, or a conversion with an addition over 150 sq ft: a separate water meter, about $19,701 in total (service line $6,560, water facilities fee $7,846, sewer capacity fee $5,295)
• a conversion with an addition of 150 sq ft or less: no separate meter, but usually an upsized meter, about $4,517

State law says ADUs created from existing space and JADUs are not a new residential use for connection fees or capacity charges unless built with a new single-family home. If you are converting existing space or adding a JADU, ask Hayward Utilities at (510) 583-4700 how this applies.

PG&E: an ADU entirely inside existing permitted space doesn't need a separate electric meter. An ADU with new space does, at the owner's cost. See our ADU cost guide and ADU financing guide. [2][3][4][6][8]

How long it takes

State law requires the city to say within 15 business days whether your application is complete, and to approve or deny a complete application within 60 days when a home already exists on the lot. Hayward says standard review times are posted on its e-Permit Portal. The city's 2023 process handout said applications "are reviewed in 15 business days and resubmittals in 10 business days," and that permits stay valid for six months with regular inspections. See our ADU permit process guide. [2][6][8]

Junior ADUs and garage conversions

A JADU is up to 500 sq ft inside an existing single-family home, for example an attached garage or a home office. You may add up to 150 sq ft only for getting in and out. Detached garages and other detached buildings can't become JADUs. A JADU needs an efficiency kitchen with a cooking appliance, a food preparation counter and storage cabinets, plus its own exterior entrance.

Shared bathroom: if the JADU shares a bathroom with the house, the owner must live in the house or the JADU, and the JADU must have an interior connection to the house. A JADU with its own bathroom has no owner-occupancy rule under state law and gets its own address. The city's checklist also calls for a deed restriction recorded with the Alameda County Clerk-Recorder's Office before the permit is issued.

A JADU without fire sprinklers needs a one-hour fire-rated separation from the house (half-hour if both have sprinklers).

Garage conversions: converting an existing, permitted garage into an ADU needs no setbacks and has no size limit. An attached garage can also become a JADU. See our junior ADU guide and garage conversion guide. [3][4][6]

Renting it out

ADUs and JADUs "shall not be utilized as commercial short-term rentals (i.e. rentals less than 30 days)." You also can't sell an ADU or JADU separately from the main house. [3][4]

Pre-approved ADU plans

You can buy a pre-approved plan directly from a designer listed in Hayward's ADU Plans Gallery. Apply under the e-Permit type "Residential - Accessory Dwelling Unit (ADU) - Using Pre-Approved ADU Plans" and add a site plan, site-specific foundation details and the ADU checklist. The city also points homeowners to the Alameda County ADU Resource Center for planning help. [2]

Permit steps in Hayward

1. Check eligibility with a planner

   Email planning.division@hayward-ca.gov or call (510) 583-4216 with your address and project description to confirm your site is eligible and what to submit. [2]

2. Register on the e-Permit Portal

   Create an account on the Hayward e-Permit Portal before you apply. [2]

3. Prepare plans and the checklist

   Have a professional prepare construction documents (site plan, floor plans, elevations, sections, details and Title 24 energy report) on 18x24 or 24x36 sheets. Complete the ADU checklist for your project type, and for a JADU with a shared bathroom include the property's legal description. [2][3]

4. Apply and pay the plan review fee

   Apply under "Residential - Accessory Dwelling Unit (ADU)" and attach your documents. Staff will send instructions to pay the plan review fee before review begins. [2]

5. Clear utilities and impact fees

   Settle water and sewer connection charges with Hayward Utilities, PG&E metering, and any park, school and affordable housing fees that apply before the permit is issued. [3][8]

6. Get your permit and build

   Pay the remaining permit fees when the permit is ready, then build and schedule inspections. [2][8]

7. Final inspection and Certificate of Occupancy

   After the final inspection passes, you receive a Certificate of Occupancy. [8]

Pre-approved and sample plans

• Hayward ADU Plans Gallery

  Pre-approved ADU plan sets you buy directly from listed designers, then submit with site-specific plans. [2]

Who to call

• Hayward Planning Division

  ADU eligibility and zoning questions

  (510) 583-4216

  [2][9]

• Hayward Permit Center

  Building permits; walk-ins Monday-Thursday 9 a.m.-1 p.m.

  (510) 583-4005

  777 B Street, 1st floor lobby, Hayward, CA 94541

  [9]

• Hayward Building Division

  Plan check and building code questions

  (510) 583-4140

  [9]

• Hayward Public Works & Utilities (development)

  Water meters and sewer connection fees for ADUs

  (510) 583-4700

  [3]

Questions people ask