Colton Zoning and ADU Guide for Homeowners

Last updated November 13, 2026. Reviewed by the Cash Home Buyers CA team.

Colton regulates accessory dwelling units in its Zoning Code, Section 18.48.150, which the City Council amended by Ordinance O-01-25 in 2025 and again by an urgency ordinance, O-01-26, to keep up with changes in state law. This guide explains what Colton publishes about ADU size, the 60-day plan check period, the application documents and the overlap with state law, and what to do if your home has an older garage conversion or unpermitted unit. Rules changed recently, so confirm current numbers with Planning before you design.

Colton ADUs at a glance

Zoning Code section	Title 18, Section 18.48.150 (accessory and junior accessory dwelling units)
Recent ordinances	Ordinance O-01-25 (2025); urgency Ordinance O-01-26 amending the section to match state law
Detached or attached ADU size	Up to 850 square feet for a studio or one-bedroom unit under the subsection quoted in the ordinance
Detached ADU height	The ordinance excerpt allows up to two stories and 30 feet for a detached ADU under one provision; confirm which applies to your lot
Plan check	60-day period from a complete application to the Building Division
Application	ADU/JADU Planning Application, plus a Public Works ADU requirements sheet
Junior ADU	Created within an existing home; state law caps it at 500 square feet

What the city publishes

The city’s ADU documents include a planning application for ADUs and JADUs, a Public Works ADU requirements summary and the ordinance text.

The application states that the plan check process for ADUs and JADUs is a 60-day period from the date a complete plan check application is submitted to the Building Division.

The Public Works sheet refers to the city’s ADU ordinance and to Government Code section 65852.2, so utility and street requirements are reviewed alongside zoning.

Ordinance O-01-25, dated February 2025, states that its purpose is to allow and regulate ADUs and JADUs in compliance with California law.

One excerpt says the maximum size of a detached or attached ADU under that subsection is 850 square feet for a studio or one-bedroom unit, and another allows a detached ADU of up to two stories with a maximum height of 30 feet.

Because the ordinance has multiple subsections with different rules for different unit types, read the full text or ask Planning which subsection applies to your lot rather than relying on one figure.

Recent changes to Colton’s ADU section

A later urgency ordinance, O-01-26, amends Title 18, Section 18.48.150 of the municipal code relating to ADUs and JADUs to comply with recent changes in state law. An urgency ordinance takes effect immediately, which means older handouts, including applications dated 2020 and 2023, may not match current rules. Ask Planning for the current application and for confirmation of any size, height, setback and parking standards before you pay a designer.

How to apply

1. Check zoning and ask Planning

Confirm your zone and whether an ADU, a JADU or both are allowed on your lot, and which subsection of Section 18.48.150 applies.

2. Complete the planning application

Use the city’s ADU/JADU Planning Application and review the Public Works requirements sheet for utility and frontage items.

3. Submit to the Building Division

The 60-day plan check period runs from the date a complete application is submitted. An incomplete package restarts the clock in practice, so confirm completeness at submittal.

4. Permit, build and finalize

Build under the permit, request inspections through the city’s process and obtain final approval. See our Colton building permits guide.

State ADU law and Colton

California’s ADU statute, Government Code section 66314 and following, sets a floor that every city must follow, and local ordinances fill in the details.

The state requires ministerial review within 60 days of a complete application, bars a city from requiring more than a limited set of standards, and generally allows an ADU or conversion inside existing space without added setbacks.

The California Department of Housing and Community Development (HCD) publishes a handbook and keeps a list of the state requirements. Because state law changes often, treat the city’s current ordinance and handout as the final word on size, height, parking and fees for your lot.

ADUs, garage conversions and selling a Colton house

Many older homes have a converted garage or a backyard unit built without permits. Buyers and lenders ask about them, and California sellers generally disclose known unpermitted work. Our guide to selling as-is with unpermitted work explains the rules, and our Prop 13 guide explains how new construction can affect property tax. Before you list:

• Check city records for permits on any ADU, conversion or addition.
• Ask Planning whether the structure could qualify under current rules.
• Estimate plans, fees and corrections needed to legalize it.
• Compare that with selling as-is and letting a cash buyer take on the legalization.

Questions to ask Planning before you design

• Does my lot and zone allow an ADU, a junior ADU, or both?
• Is a pre-approved or pre-reviewed ADU plan available?
• What are the current impact, utility and school fees for the size I am considering?
• Can my existing garage or accessory structure be converted without changing its footprint?
• Are there fire, slope, easement or utility constraints on my lot?

Junior ADUs and garage conversions in more detail

State law treats a junior ADU as a unit of up to 500 square feet created inside the walls of an existing or proposed single-family home, with an efficiency kitchen and a recorded restriction that keeps it from being sold apart from the house.

A garage conversion is a different path: the unit replaces the garage, and state law generally does not require the city to demand replacement parking. Both are common sources of unpermitted space in older Colton neighborhoods, which is why buyers’ agents and appraisers ask for the permit record.

If a conversion was done without a permit, the usual fix is to submit as-built drawings, pay the fees and pass inspection, which can take months and cost real money.

Fees, utilities and property tax

State law limits the impact fees a city can charge on smaller ADUs and on conversions of existing space, and it limits when a separate utility connection can be required.

Larger new units can still carry impact fees, school fees and water or sewer connection charges, so ask for an itemized estimate before you commit to plans. New construction is generally reassessed for property tax under Prop 13, which means an ADU can raise the bill for the whole property. Our Prop 13 guide explains how reassessment works.

Why ADUs matter for resale

A permitted ADU can add rental income and appeal for some buyers, but an unpermitted one can complicate financing and appraisal. Lenders typically want permitted living area, and an appraiser may not count unpermitted space.

Because an ADU generally cannot be sold separately from the main home, its value comes through the sale of the whole property.

If you inherited a house with an old backyard unit, or bought one with a converted garage, check what the city has on file before you decide how to sell. Our probate home sale guide covers inherited property.

How to sell a house in Colton

1. Ask the city for the permit record on any ADU or conversion.
2. Collect plans, inspection records and any city notices.
3. Request a no-obligation cash offer for the house as it stands.
4. Choose your closing date.
5. Close with no repairs, legalization or showings required.

See also our Colton page, the Colton as-is sale page, the Colton fast-sale page, the Colton cash offer process and the San Bernardino County hub.

Frequently asked questions

Where are Colton’s ADU rules?

In the Zoning Code, Title 18, Section 18.48.150, as amended by Ordinance O-01-25 and the urgency ordinance O-01-26.

How long does Colton take to review an ADU?

The city’s application says the plan check process for ADUs and JADUs is a 60-day period from the date a complete application is submitted to the Building Division.

How big can a Colton ADU be?

The ordinance excerpt we read gives 850 square feet for a studio or one-bedroom detached or attached ADU under one subsection. Ask Planning which standard applies to your lot.

Has Colton updated its ADU rules recently?

Yes. Ordinance O-01-25 was dated February 2025, and urgency Ordinance O-01-26 amends Section 18.48.150 to comply with recent state-law changes.

Can I convert my garage to an ADU in Colton?

State law allows garage conversions, and Colton’s ordinance is written to follow it. Get a permit and confirm the current standards with Planning.

Can I sell my Colton house with an unpermitted ADU or garage conversion?

Yes. You can disclose it and sell as-is, including to a cash buyer. Our statewide guide explains the disclosure rules.

More guides

• We Buy Houses in Colton
• We Buy Houses in San Bernardino County
• San Bernardino County Property Tax Guide
• Colton Building Permits Guide
• Colton Code Enforcement Guide
• Sell a Colton House As-Is
• Colton Cash Offer Process
• Redlands Building Permits Guide
• All California Guides

Sources

• City of Colton: Ordinance No. O-01-25
• City of Colton: ADU/JADU Planning Application
• City of Colton: Public Works ADU Requirements Summary

This guide is general information from public sources, not legal advice. Confirm current rules, fees and hours with the city.