Build an ADU in Modesto, California

Browse ADU plans, match with builders, and learn what you can build in Stanislaus County
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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.

Detached 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. eg “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?

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