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  • WILLBII INC

Floor Plans for Accessory Dwelling Unit. Check with State & City Laws Regarding your ADU Size Limits

There are many things to consider when designing the perfect ADU. First step is to check in with your local city. In September 2022 new bill has pass regarding ADU Development. Most city employees are not up to date with state regulations so beware and please check your local city websites for any information. For size requirements please also check the state legislative bills. The state legislative bills are rules for each city to follow. These bills makes it easier to build your ADU. Example: Maximum ADU Size for a 800 square fee ADU in Arcadia California law is not up to date with the state law. The state law minimum sq ft is 850 for a detached ADU. Example 2: Pasadena is requiring all JADU have a kitchen. Some cities may allow up to 1,2000 square feet. All these sizing regulations may put a hamper in your dream of having the perfect ADU. I strongly recommend you to check in with your builder and state planner for guidance.

Once you know the size of ADU you can build, then the next step is to get a floor plan. There are many example floor plans you can download. The other option is creating your own plan with an architect, but that will be very expensive. You may find them over the internet or search on google images, but all of these must meet city requirements when submitting to the city planner. Off the shelf Floor plans are not always perfect so beware. I have complied some city approved plans from San Diego as reference. You can see what a typical ADU Floor plan may look like. Most ADU developers will offer their own layouts to choose from when choosing a builder. This is because they have calculated the materials, finishes and furnishings to fit within their layouts. A custom floor plan will cost you more money so keep that in mind.


(Example floor plans below)

Example Floor Plan A.


1200 square feet three bedrooms, 1 bath.



1200 square feet two bedroom two baths


1200 square feet 2 bedroom 1 bath


1000 square feet two bedroom 1.5 bath


800 square feet 1 bedroom, 1 bath


600 square feet one bedroom, 1 bath


Now that you have a general idea of floor plans then after the next step is to get it approved. The planning process will take one or two months. The builder will go back and forth with the city in obtaining building permits. Once everything is approved, the constructions of an ADU will take 1-6 months to complete.

The construction process of the ADU will start with the foundation, water lines, electric, utilities, framing, and other dozens of variables, but that is another blog topic and I won't be covering today. Hopefully by now I have given you a better sense on sizing, layouts and city restrictions when building your ADU. I wish you a smooth journey ahead.

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