Home builder
ADU Construction in Fontana, CA
Castillos Construction Services builds ADUs for homeowners in Fontana and across the Inland Empire.
Expert ADU Construction in Fontana, CA
ADU construction adds a fully separate living space to your existing property. Castillos Construction Services handles this work for homeowners across Fontana, Riverside, Rancho Cucamonga, Upland, Monrovia, Highland, and Jurupa. Whether you want a detached backyard unit, an attached addition, or a garage conversion, we build to California code on a permanent foundation. Fontana permits ADUs in all residential and mixed-use zones, and detached units can reach up to 1,200 square feet under current state and city rules. Many Fontana lots, especially in older neighborhoods, have more usable backyard space than homeowners expect. Our background spans decades of hands-on construction work, so we read a lot, spot constraints early, and build what the plans call for. If you want to house a family member, create a rental unit, or add livable square footage without moving, an ADU is a practical path. Call us to talk through what your Fontana property can support.
What's included
- Adds a fully independent living space to your property without requiring you to move
- Detached ADUs in Fontana can reach up to 1,200 sq ft, giving real room for family or tenants
- A permitted ADU increases your property's assessed improvements and resale appeal
- Garage conversions and new detached builds both qualify under Fontana's ADU-friendly zoning
- Multigenerational households get a private, code-compliant space for parents or adult children
- We serve Fontana, Rancho Cucamonga, Riverside, Upland, Highland, Monrovia, and Jurupa from one team
Licensed General Contractor
New Home Construction
ADU Specialist
Renovation & Addition Expert
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FAQ
ADU Construction FAQ
Common questions about adu construction in Fontana, CA.
Yes, Fontana allows detached ADUs on residential lots up to 1,200 square feet. A minimum 4-foot rear setback applies for new construction under current California and city rules.
Yes, we serve Rancho Cucamonga, Riverside, Upland, Highland, Monrovia, and Jurupa in addition to Fontana. Each city follows California ADU law with its own local requirements.
Fontana allows attached ADUs, detached ADUs, garage conversions, and Junior ADUs on qualifying residential lots. The right type depends on your lot size, layout, and goals.
Owner occupancy is not required for ADUs in Fontana under current California rules. You can rent the unit out on a term of 30 days or longer.
Yes, garage conversions into permitted living spaces are allowed in Upland and Jurupa under California ADU law. The existing structure must meet building code requirements for habitable space.
A Junior ADU is carved out of the existing home's footprint and is limited to 500 square feet, while a full ADU can be a separate detached or attached structure up to 1,200 square feet. Owner occupancy is required on the property when a Junior ADU is built.
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Find Us
Proudly Based in Fontana, CA
Stop by, call, or book online — we're always nearby when you need us.
Phone
(909) 430-8752Hours
- Monday 8:00 AM - 5:00 PM
- Tuesday 8:00 AM - 5:00 PM
- Wednesday 8:00 AM - 5:00 PM
- Thursday 8:00 AM - 5:00 PM
- Friday 8:00 AM - 5:00 PM
- Saturday Closed
- Sunday Closed