ADUs in Fontana
Backyard homes for Fontana, priced before you sign.
We design, permit and build standard ADU models in Fontana and across the Inland Empire. You pick a model, we assess your lot, and you get one all-in price before you sign.
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The models
Four standard homes, each with a price up front.
Starting prices include design, permitting and construction with standard finishes. Site work and utilities generally run $15,000 to $35,000 and are priced after we see your lot, and city permit fees are billed at cost. All four are under the City's 1,200 sq ft limit for its own ADUs. See what's included.
Around the Inland Empire
Buildoly projects in the western Inland Empire.
Each pin is a Buildoly project between Ontario and Riverside. See the full map.
Fontana ADU rules in plain English
What you can build in the City of Fontana.
The basics for a single-family lot in Fontana, under the ADU rules the City updated in 2026. Every lot is different, so we confirm each of these for your address before we price anything.
How many
Up to two ADUs and a junior ADU
Under the state-law path in the City's code: one ADU inside the house or an existing accessory building, one junior ADU, and one new detached ADU of up to 800 sq ft. The City also allows its own ADUs of up to 1,200 sq ft, and we confirm with Planning how one fits with the others on your lot.
Fontana Code 30-467(e)(1)Size
Up to 1,200 sq ft
A City-standard detached ADU can be up to 1,200 sq ft. An attached one is held to half the house or 1,200 sq ft, whichever is less, but never less than 800 sq ft. The state-law detached ADU is capped at 800 sq ft.
Fontana Code 30-467(g)(1); (e)(1)(b)(2)Height
16 ft for a detached ADU
Every detached ADU can be 16 ft tall, or 18 ft within a half-mile walk of major transit, and up to 20 ft there to match the house's roof. A City-standard detached ADU is one story. An attached ADU can be 25 ft or the zone's limit, whichever is lower, and two stories at most.
Fontana Code 30-467(f)(2); (g)(8)Setbacks
4 ft side and rear, 18 ft front
The 18 ft front setback applies to City-standard ADUs and can't push one under 800 sq ft. An ADU rebuilt in the same place and size as a legal existing structure needs no setback.
Fontana Code 30-467(g)(2); (e)(1)(b)(1)Parking
One space, with exceptions
A City-standard ADU needs one off-street space, unless it's within a half-mile walk of transit, within a block of a car-share stop, in a historic district, part of the house or an accessory building, or where street permits aren't offered. State-law ADUs need none, and lost garage spaces don't have to be replaced.
Fontana Code 30-467(g)(5)Owning and renting
Rent for 30 days or more
You don't have to live on the property to have an ADU. It can be rented, but not for less than 30 days, and it can't be sold apart from the house except as state law allows.
Fontana Code 30-467(f)(4), (f)(5), (f)(7)Worth knowing in Fontana
A junior ADU needs the owner living on site only when it shares a bathroom with the house. Every junior ADU needs a deed restriction recorded before the building permit.
Many Fontana lots are zoned under a specific plan. Whether a plan's own standards also apply to an ADU is a question we take to Planning for your lot.
Changing on January 1, 2027
SB 1117 limits the impact fee on an ADU over 750 sq ft to the area above 750 sq ft, in proportion to the main house, for up to two ADUs on a lot. ADUs of 750 sq ft or less still pay no impact fee.
AB 956 lets you build two new detached ADUs on a single-family lot through the state's approval path. On that path a city can cap each one at 800 sq ft.
Sources: Fontana Zoning and Development Code Sec. 30-467, as amended by Ordinance No. 1983, adopted February 24, 2026, in effect March 26, 2026; California Government Code sections 66310 to 66342; SB 1117 and AB 956 (2026). Checked November 2026.
How it works
From your lot to move-in.
Step 1
Pick a model
Choose a model and finishes online, or book a free consultation to talk it through.
Step 2
Site assessment
We visit your lot, check utilities, access and the City's rules, and give you one all-in price before you sign.
Step 3
Design and permits
We finish the plans and run the permit with the City of Fontana from submittal to approval.
Step 4
Build and move in
We build on site and manage the job through final inspection and your certificate of occupancy.
Typical timeline: 8 to 12 months from start to finish. About 1 month of design, 2 to 4 months of permits and 3 to 5 months of construction. Your lot and the City's review times can move it.
Fontana ADU questions
What Fontana homeowners ask us.
Our models start at $165,000 for Model S, $195,000 for Model 1, $270,000 for Model 2, $360,000 for Model 3. Those are all-in starting prices for design, permitting and construction. Site work and utilities generally run $15,000 to $35,000, and we price yours after the site assessment, before you sign. City permit fees are separate: your city sets them and we bill them at cost. You start with $1,000, credited in full to your contract, and many of our clients finance the whole build through our lending partners, subject to credit approval. See what's included in the price.
A City-standard detached ADU can be up to 1,200 sq ft and one story. An attached one is held to half the house or 1,200 sq ft, whichever is less, but never less than 800 sq ft. A detached ADU built under the state-law path is capped at 800 sq ft. All four of our models are under 1,200 sq ft. We check the exact limit for your lot.
Our typical timeline is 8 to 12 months from start to finish: about 1 month of design, 2 to 4 months of permits and 3 to 5 months of construction. Your lot and the City's review times can move it either way, and we give you a schedule for your address after the site assessment.
A City-standard ADU needs one off-street space, which can be tandem or in a setback area, unless it's within a half-mile walk of public transit, within one block of a car-share stop, in a historic district, part of the house or an accessory building, or where on-street permits are required but not offered to the occupant. ADUs built under the state-law path need none, and spaces lost to a garage conversion or demolition don't have to be replaced.
The City charges no impact fees on an ADU under 750 sq ft. A larger ADU pays them in proportion to its size compared with the house. A converted ADU on a single-family lot needs no new utility connection and pays no connection fee or capacity charge. School district fees are separate.
Yes. We build across the Inland Empire, as well as Los Angeles County, Orange County and San Diego. Each city has its own ADU rules and plan check, and we confirm them for your address. Enter your address in our quote tool to check that you're in our service area.
Where we build
We also build in these cities.
Each city page covers that city's ADU rules and who issues the permit. All cities.
Los Angeles County
Orange County
San Diego County
Inland Empire
See your price for a Fontana ADU.
Pick a model and tell us your address. After the site assessment you get one all-in number, before you sign.