Rialto, CA Building Setbacks & Zoning: Lot Coverage Limits (2026)

030 of the Rialto Municipal Code sets the lot, yard and height requirements for the R-1 single-family zone, the city's standard residential district. Subsection I fixes maximum building coverage at 30 percent of the total lot area, meaning no more than three-tenths of an 8,400-square-foot minimum lot, or 2,520 square feet, may be covered by roofed structures once a lot is built at the zone minimum. The same section requires a minimum lot width of 80 feet and a minimum lot depth of 100 feet, and sets a minimum dwelling size of 1,440 square feet with a median and average of 1,600 square feet, exclusive of garages, porches and eaves.

030 additionally limits any detached accessory building to 25 percent of the rear yard even when the 30 percent citywide cap is not reached. 070(S), if the 30 percent lot coverage limit would block an attached or detached ADU of at least 800 square feet, the city must still allow construction of an ADU up to 800 square feet as long as every other development standard is met. Applicants who need relief from the 30 percent standard for a project other than an ADU must seek a variance or other discretionary approval; the code does not authorize an administrative waiver of the coverage limit outside the ADU exception.