Residential
ADU Design & Permitting in Ontario
ADU Design & Permitting for Ontario owners, reviewed by City of Ontario Building Department, typically 6 to 12 weeks to permit, faster where a preapproved plan set applies.

Inland Empire · San Bernardino County
Whether your parcel sits inside Ontario Ranch changes the rulebook entirely. Confirm that first, before anyone draws anything. Plan review here runs through City of Ontario Building Department, with Ontario Ranch specific plan review in the south, with Ontario Fire Department on access and life safety. Typical experience is roughly 6 to 12 weeks to permit, faster where a preapproved plan set applies.
Large volumes of newer tract housing in the south and pre-war stock downtown. On the commercial side, distribution, cold storage and airport-adjacent commercial fit-outs. Those two facts explain most of what is easy and most of what is expensive here.
Ontario Ranch carries specific plan and infrastructure fees that older parts of the city do not. We put the local fee picture into the first budget, because a number that ignores school, sewer and utility charges is not a budget, it is an advertisement.
We work throughout Ontario ZIP codes 91758, 91761, 91762 and 91764, including Ontario Ranch, Downtown Ontario, Creekside, Rosena. Two addresses in the same ZIP can still sit under different overlays, so we review the parcel rather than the postcode.
Ontario Ranch · Downtown Ontario · Creekside · Rosena
Residential
ADU Design & Permitting for Ontario owners, reviewed by City of Ontario Building Department, typically 6 to 12 weeks to permit, faster where a preapproved plan set applies.
Residential
Garage Conversions for Ontario owners, reviewed by City of Ontario Building Department, typically 6 to 12 weeks to permit, faster where a preapproved plan set applies.
Residential
Additions & Remodels for Ontario owners, reviewed by City of Ontario Building Department, typically 6 to 12 weeks to permit, faster where a preapproved plan set applies.
Commercial
Tenant Improvements for Ontario owners, reviewed by City of Ontario Building Department, typically 6 to 12 weeks to permit, faster where a preapproved plan set applies.
Commercial
Restaurant, Retail & Hospitality for Ontario owners, reviewed by City of Ontario Building Department, typically 6 to 12 weeks to permit, faster where a preapproved plan set applies.
Residential
Permitting & Plan Check for Ontario owners, reviewed by City of Ontario Building Department, typically 6 to 12 weeks to permit, faster where a preapproved plan set applies.
Commercial
Construction Management for Ontario owners, reviewed by City of Ontario Building Department, typically 6 to 12 weeks to permit, faster where a preapproved plan set applies.
Commercial
Design-Build for Ontario owners, reviewed by City of Ontario Building Department, typically 6 to 12 weeks to permit, faster where a preapproved plan set applies.
City of Ontario Building Department, with Ontario Ranch specific plan review in the south. Fire review runs through Ontario Fire Department. Whether your parcel sits inside Ontario Ranch changes the rulebook entirely. Confirm that first, before anyone draws anything.
Typically roughly 6 to 12 weeks to permit, faster where a preapproved plan set applies. The variable is correction cycles, not intake speed, which is why we spend the extra week making the first submittal complete.
Most commonly: Ontario Ranch specific plan standards; Airport noise contours around ONT; Industrial corridor standards along Mission and Holt. Which ones touch your parcel is an address question, and we answer it during feasibility.
Ontario Ranch carries specific plan and infrastructure fees that older parts of the city do not. We put those numbers into the first budget rather than presenting them as a later surprise.
Yes, across Los Angeles and Orange County from offices in Santa Monica and Fullerton. Nearby markets we cover include Rancho Cucamonga, Chino Hills, Fontana, San Bernardino.
Send the address, including the ZIP code, and what you want to build. We come back with what the City of Ontario Building Department route looks like, a realistic budget range and a schedule.