Every city in California has slightly different standards and rules for their accessory dwelling units (ADUs.) If you’ve been looking into California’s standards for ADUs you will also have to look into the local rules in your city. If you want to know what’s the biggest ADU you can build in Hayward; it’ll depend on a few factors, including the size of your home. Here’s what you need to know.

ADU Size Rules in Hayward

All ADUs in Hayward need to comply with the local ordinances found in SEC. 10-1.2740 – Accessory Dwelling Units, which is found in the municipal code. These rules do stipulate a maximum size. It is either 1,200 square feet or 50% of the habitable floor area of your existing home, whichever is less.

This means that the absolute largest ADU you can build is 1,200 square feet. However, you may not be able to build even that large of an ADU. You’d need 2,400 or more habitable square feet in your existing home to be able to an ADU of the maximum size. If your home is 2,000 square feet, then you would only be able to build an ADU that is 1,000 square feet.

Other Size Considerations

That’s not where the size rules end for ADUs in Hayward. There are other limitations that you’ll have to consider before you finalize your design. They include:

• Bedroom limits: An ADU in Hayward cannot have more than two bedrooms. It can have less.
• Property line setbacks: There are multiple rules governing how far an ADU must be from the property line, whether they are attached or detached to the existing home. If you’re converting a garage for your ADU it must be set back from all property lines at least five feet. It must also conform to the rules for setbacks for Building and Fire standards, even if they require a larger setback. If you have a corner lot then you also need to abide by the unique setback rules for them.
• Height restrictions: Your ADU also can’t be too tall. If it is attached to your home, it needs to be only as tall as allowed by the rules for the primary structure on the property. If it is detached from your home, then it needs to follow the rules for detached, accessory and secondary structures.

There are other rules that may incidentally affect the size of ADU that you can build. For example, ADUs need to have their own front door, separate from the main home. You’ll need to account for that space in your design. While the ADU can sometimes impede on space that you now use for parking, the property as whole still need to provide parking according to the rules set out in Hayward’s local ordinances.

Need Help with ADU Rules?

The ADU rules in Hayward, and California in general, are fairly complex. As ADU builders, we have plenty of experience explaining these rules and creating designs that are legal, as well as beautiful and functional.