Building an ADU in Modesto, California

Learn permits, rules, and guides to building in Stanislaus County
No items found.

Overview

Modesto is located in Stanislaus County in California. Modesto has a total population of 201165 over a land mass of 36.87 Square Miles. When it comes to ADUs, the city allows for 1+ ADUs on a given property, and a square footage of 850-1,000 sf

Number of ADUs Allowed

1+

Size of ADU Allowed

850-1,000 sf

Types of ADUs Allowed

Detached, Junior, Attached

Permit Cost

Coming Soon

Number of ADUs allowed

According to state law, all single-family homes are allowed at least one Accessory Dwelling Unit. Additionally, single-family parcels which are owner-occupied may create one Accessory Dwelling Unit and one Junior Accessory Dwelling Unit. Also, multi-family parcels may now add one ADU per every four existing residential units, so long as they were legally established.

Property Requirements

Single-family and multi-family Lots will be allowed to construct up to 850 sq.ft. for a one bedroom ADU or up to 1,000 sq.ft. for a two bedroom ADU, regardless of the underlying zoning standards of the property. A Junior ADU up to 500 sq.ft. is allowed. The minimum size of any living unit (including ADUs and Junior ADUs) is 150 sq.ft. according to Califronia Residential Code. ~ Updated: State Law AB-68

Types of ADUs Allowed

Attached ADU

An attached ADU is one that is attached to your house. Also know as Addition ADUs or “bump-out ADUs. These types of ADUs can be accessed from the primary house with a door in the connection point, but also can be independent of the main home.

Dettached ADU

A detached ADU is not connected to your primary house. The dwelling needs to be within your property setbacks and allowable building size (both height and square footage).

Junior ADU

Junior Accessory Dwelling Units (JADUs) are named this way because they are small (up to 500 square feet).

In California, the recent state bills AB68 and AB 881 permits both an ADU and a Junior ADU (JADU) on the same lot with a proposed or existing single-family dwelling. This means you can have two units on your lot: ADU, and JADU.

Property Requirements

Ownership
Owner-occupancy will not be required for new Accessory Dwelling Units (conversion and new construction) built between 2020 and 2025. ~ Updated: State Law SB-13
Number of ADUs Allowed
According to state law, all single-family homes are allowed at least one Accessory Dwelling Unit. Additionally, single-family parcels which are owner-occupied may create one Accessory Dwelling Unit and one Junior Accessory Dwelling Unit. Also, multi-family parcels may now add one ADU per every four existing residential units, so long as they were legally established.
ADU Size
Accessory Dwelling Unit (ADU) projects on single family or multi-family residential parcels will not be subject to the minimum lot size of the underlying local zoning code or by special ordinance. ~ AB-68
Parking
Replacement parking shall not apply to parcels which convert an existing garage to an Accessory Dwelling Unit or Junior Accessort Dwelling Unit (JADU). ~ According To AB68
Height
The maximum height of an ADU is not specified in the state standards. If ADU maximum height is not established locally, the height limitations of the underlying zone shall apply. ~ State Standards
Fire Safety
Accessory dwelling units shall not be required to provide fire sprinklers unless they are also required for the primary dwelling. ~ State Standards
Utility Connections
Connection and utility fees shall be reasonable, and shall not be disproportionately higher than those to develop primary dwellings, so as not to deter the development of ADUs. If a private sewage disposal system is used, such as a septic system, review and approval by a local health officer may be required. ~ State Standards
Aesthetic
Specific design styles and restrictions are not specified under State Standards. Passageways shall not be required in conjunction with the construction of an accessory dwelling unit. ~ State Standards
Set backs
Setbacks for a detached new construction Accessory Dwelling Unit (ADU) shall be no more than 4 ft from the rear and side lot lines. No setbacks shall be required for Accessory Dwelling Unit (ADU)s and JADUs converted from legally eastablished existing space. Attached new construction Accessory Dwelling Unit (ADU)s and conversions from existing space to be expanded must comply with the setbacks of the underlying zone. ~ AB-68

Design Review

The municipality shall provide a ministerial review process which is not based on a discretionary approval for an ADU. The process shall take no less than 120 days. Valid applications submitted for ADUs, if not approved or denied within 120 days from submission, shall be considered approved. ~ State Standards

Next Steps

To get started on your ADU, here are some first steps.

Call Your City

Search Google for your city’s contact number. An example would “City of Phoenix Residential Permits Contact Number”

You can call the main line and get directed to the permitting department.

Ask these questions...

1) Can I put a secondary home on my lot (Accessory Dwelling Unit)
2) What are my livable setbacks, and ADU size regulations?
3) Can I put a prefabricated guest house on my property?

Get Started With a Modular Home

Find a Modular Home

Use our prefab discovery tool to help you find the perfect home.

Get a Site Analysis

See what can go on your property. A site Analysis is the first step for any construction

Start with a Site Analysis