Highland Zoning and ADU Guide for Homeowners

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

Highland allows one ADU per residential lot, and one ADU plus one junior ADU on a single-family lot, with ministerial review and a city decision within 60 days of a complete application. This guide summarizes Highland Municipal Code section 16.44.180 for homeowners, including where ADUs are not allowed, size and height limits, setbacks, parking and rental rules, and what an ADU or garage conversion means when you sell.

Highland ADUs at a glance

Governing code	Highland Municipal Code section 16.44.180 (accessory dwelling units)
Number allowed	One ADU per residential lot; one ADU plus one JADU on a single-family lot
Not allowed	High fire hazard severity zones and lots served by septic systems (section 16.44.180(D)(1))
Review	Ministerial; city acts within 60 days of a complete application
Pre-reviewed plans	The city runs a Pre-Reviewed ADU Plan Program
Rentals	31 days or longer
Sold separately?	No, except by a qualified nonprofit under state law

Where ADUs are not allowed

Highland’s code bars ADUs in high fire hazard severity zones and on lots with septic systems. Check your parcel before you plan: a lot that looks suitable may fall in a restricted area. The city’s ADU page and Planning staff can confirm where a specific address falls.

Highland ADU standards

Attached ADU size	Up to 50 percent of the primary home’s floor area, except that 850 sq ft is allowed (1,000 sq ft if more than one bedroom)
Largest unit	Units with two or more bedrooms are capped at 1,200 sq ft
Detached new construction	The code table lists up to 800 sq ft
JADU size	150 to 500 sq ft, within the existing or proposed primary home
Height	16 or 18 feet, following Government Code section 66321(b)(4)
Setbacks	None for conversions of existing space; 4 feet at the side and rear otherwise; a front setback applies unless it would prevent an 800 sq ft ADU
Parking	One space per ADU, with exceptions; none for a JADU

Parking exceptions

The city lists several exceptions to the one-space rule: the ADU is within a half mile of public transit, sits in a historic district, is part of the existing home or an accessory structure, is in an area where on-street permits are required but not offered to occupants, or is within one block of a car-share location. No replacement parking is required when a garage is converted.

Design and occupancy rules

• The ADU must use colors and materials that match the primary home.
• An attached ADU needs a separate entrance.
• Fire sprinklers are required only if the primary home needs them.
• A JADU needs an efficiency kitchen, an entrance separate from the main entrance, and a recorded deed restriction against separate sale.
• The owner must live in the primary home or the JADU.
• Rentals must be for 31 days or longer.

How the Highland process works

1. Check eligibility. Confirm that the lot is outside a high fire zone and not on septic.
2. Consider a pre-reviewed plan. The city’s program may shorten design work.
3. Get service letters. Letters of service availability for water and sewer are needed before the building permit.
4. Apply for permits. Review is ministerial, and the city acts within 60 days of a complete application. Its ADU packet says the first plan review takes 10 business days and later reviews 5.
5. Pay fees. Impact fees apply except where state law exempts them, and school fees may apply.

ADUs, garage conversions and selling a Highland 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, remembering the fire zone and septic limits.
• 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

• Is my lot inside a high fire hazard severity zone, and is it on a septic system?
• Does a pre-reviewed ADU plan fit my lot?
• What are the current impact and school fees for the size I am considering?
• Do water and sewer providers need to issue service availability letters, and how long do they take?
• Can my existing garage or accessory structure be converted without changing its footprint?

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 cannot be sold separately from the main home, its value comes only through the sale of the whole property.

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

Fees, utilities and property tax

Impact fees apply to Highland ADUs except where state law exempts them, and school fees may apply to new living area. Water and sewer service letters are required before the building permit, so contact the providers early. New construction is reassessed under Prop 13, which means an ADU can raise the property tax bill. Ask the city for a current fee estimate for your project size before you commit to plans.

Junior ADUs in more detail

A junior ADU is carved out of the existing or planned primary home and is limited to 500 square feet, with a minimum of 150. It needs an efficiency kitchen, a separate entrance from the main entrance, and a recorded deed restriction that prevents separate sale.

Because the owner must live in either the main home or the JADU, a JADU is a poor fit for an investor-owned rental unless the owner moves in.

How to sell a house in Highland

1. Check which structures on the property are permitted ADUs, conversions or unpermitted.
2. Collect permits, plans 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 legalization, repairs or showings required.

Our local pages cover related situations in Highland, including selling as-is, selling fast, cash home buyers and the cash offer process. See also our Highland page and the San Bernardino County hub.

Frequently asked questions

How many ADUs can I build in Highland?

One ADU per residential lot, or one ADU plus one junior ADU on a single-family lot.

Where are ADUs not allowed in Highland?

The code does not allow ADUs in high fire hazard severity zones or on lots served by septic systems.

How long does Highland take to review an ADU?

The city acts within 60 days of a complete application. Its ADU packet says the first plan review takes 10 business days and later reviews 5.

Do I have to live on the property if I build an ADU in Highland?

The owner must occupy the primary home or the JADU.

Can I sell a Highland ADU separately?

No, except by a qualified nonprofit under state law. A JADU also needs a deed restriction against separate sale.

Does an ADU need parking in Highland?

One space per ADU is required, with exceptions such as being within a half mile of transit. A JADU needs none, and no replacement parking is required for a garage conversion.

Can I sell my Highland 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 Highland
• We Buy Houses in San Bernardino County
• San Bernardino County Property Tax Guide
• Highland Building Permits Guide
• Highland Code Enforcement Guide
• Yucaipa Building Permits Guide
• Yucaipa Code Enforcement Guide
• Yucaipa Zoning and ADU Guide
• Redlands Building Permits Guide
• All California Guides

Sources

• Highland Municipal Code section 16.44.180: Accessory Dwelling Units
• City of Highland: Accessory Dwelling Units
• California HCD: Accessory Dwelling Units

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