Temecula, CA Environmental Rules: Flood Elevation Requirements (2026)

150(C) of the floodplain management chapter sets the baseline standard: new residential and nonresidential construction, plus substantial improvements, must have a pad elevation at least one foot above the FIRM base flood elevation, verified twice, once at permit issuance and again once the lowest floor is complete, both times by a registered professional engineer or surveyor filing FEMA's Elevation Certification Form with the floodplain administrator. 140. Nonresidential buildings have an alternative: instead of raising the pad, they can be floodproofed watertight with walls able to resist hydrostatic and hydrodynamic loads, certified by a registered engineer or architect on FEMA's standard form.

Any fully enclosed area below the lowest floor used only for parking, building access, or storage must include flood vents that equalize hydrostatic pressure automatically, at least two openings totaling one square inch of net area per square foot of enclosed space, with the lowest opening no higher than one foot above grade. Attached garages built with the floor slab below the base flood elevation must be designed for automatic floodwater entry and built with flood-resistant materials below that line; small detached garages and low-cost accessory structures get a narrower exception if they meet the same flood-resistant-material, anchoring, and floodway-encroachment standards. 180.