ADU Riverside’s Regulations and Permits Explained 2024
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ADU Riverside’s Regulations and Permits Explained 2024

|Oct 28, 2023

Building an ADU in the Riverside can be a great asset to have, but it has some regulations and requirements that you need to follow. These regulations and requirements would make the permit process much easier and allow you to build your accessory dwelling unit with ease.

This article would cover everything, from the number of ADUs allowed to land permits and approval requirements, so read on to stay informed.

Riverside County ADU Requirements

Number of ADUs Allowed

The number of ADUs allowed in Riverside depends on the primary dwelling. With one single-family residential lot, you can build one junior and one detached ADU. However, keep in mind that the size of the junior ADU must not exceed 500 square feet.

Parking Requirements

As far as the parking requirements are concerned, you aren't necessarily required to build one if your interior ADU is within the existing structure. However, for detached ADUs built separate from the primary dwelling, you will be required to build one regular parking space per unit. Moreover, keep in mind that this requirement rules out if you live only half a mile walking distance away from transit, such as a train station or bus stop.


To build an ADU, it is necessary that you own a primary dwelling in the area. Moreover, the place where your primary residence is located must have all required building permits to have permission for additional accessory dwellings. On the other hand, if water availability, sewage disposal, and other public health safety measures are not ensured, then ADU would not be allowed to be built.

Riverside County ADU Requirements

Design Requirements

Before you go ahead with your ADU construction, make sure you have a design plan that demonstrates compliance with the development standards of Riverside. The design would also make it easy for you to process the documents and permits.

Land Permits

For an accessory dwelling, you don’t need a conditional use permit or plot plan. All you need is to submit an application to build an additional ADU in Riverside County. The processing of the application would be done in accordance with the ordinance no. 457 and 671.


The processing of the application would take around 60 days to be processed. The process results would let you know if your design plan matches with the building requirements or if it still has some corrections to be made. The processing time for an accessory time is more than the time it takes to process the application for a primary dwelling on the same lot.

Utility Connection Requirements

A separate utility connection will not be a necessary requirement for your secondary dwelling unit built within the house, which means that you use the same source for junior or interior ADU power. However, an attached ADU would require a separate utility connection to fulfill Riverside County's ADU requirements. The connection and impact fees will be calculated in accordance with government code sections 65852.22 and 65852.2.

Utility Connection Requirements

Riverside County Setback Requirements

To make sure that your design matches the building and setback requirements for accessory dwellings, here are some things that you need to consider.

Lot size

The lot size of your accessory dwelling unit built inside the house would be considered a part of your primary dwelling, so you don't need to worry about the size requirements there. However, detached ADUs have different rulings for different-sized primary dwellings. For instance, you can build guest quarters or detached second units only if your primary dwelling is zoned for one-family dwelling and is located on an area above 7200 square feet. On the other hand, multiple-family dwellings can have separate detached ADUs built at a size smaller than the main dwelling.


For interior and junior ADUs, you must keep them under the zoning of your house. It would keep them a part of your primary dwelling and compliant with no other setback restrictions than the ones you have for your dwelling. However, detached and attached ADUs should have their side and rear setbacks more than 4 feet from the primary dwelling. If you decide to add a guest quarter or second unit, the same zoning classification will be followed as your main dwelling.


To build an ADU, you must have an additional habitable area within the boundaries of your house. The habitable area can be finished attics and basements, but not garages or other accessory structures or buildings. Moreover, keep in mind that your accessory dwelling cannot exceed more than 50 percent of your primary dwelling's floor size, and the maximum size for a detached ADU under any condition is 1000 square feet.

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Riverside County Tiny House Laws

To build an ADU or a tiny house within the boundaries of your primary dwelling, here are the laws that you must know


If you decide to build an ADU on the same lot where the primary dwelling is located, you will not be allowed to occupy the ADU or live in it if it is permitted between 1st January 2020 to 1st June 2025. ADUs permitted after 2025 would be allowed for the owners to live in. In addition, junior ADUs are not compliant with such restrictions. You can live or occupy your junior ADU without as many issues as you would go through in detached ADU occupancy.

Fire Protection 

Fire protection is a must regardless of the type of ADU you are going to build for your house. A water supply must be enough to keep your junior or detached ADU safe from fire. Junior ADUs are required to have fire sprinklers on if your primary dwelling comes under a similar requirement.

Riverside County Tiny House Laws


An ADU in Riverside Country can be great to have, since you can enjoy and relax your time off from worldly affairs in a calm and composed environment. However, staying informed of the regulations is also extremely important. We hope this article was a useful one for you, and that you will take care of all the requirements needed to have an ADU of your own.

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