Upper Darby, PA Environmental Rules: Flood Elevation Requirements (2026)

Section 305-24 opens by prohibiting new construction or substantial improvement anywhere in an identified floodplain area outright; a property owner may only build after obtaining a variance under Article VII. Once a variance is granted, residential structures in AE, A1-30 and AH zones must have their lowest floor, including the basement, elevated "up to, or above, the regulatory flood elevation" (Section 305-24A(1)). " In A zones without a mapped base flood elevation, the Floodplain Administrator sets the required elevation under Section 305-19C; in AO zones, the lowest floor must sit at or above the highest adjacent grade plus the depth number printed on the FIRM.

Nonresidential buildings get an alternative under Section 305-24B: instead of elevating, they may be floodproofed watertight to the regulatory flood elevation using the W1/W2 standards from the Army Corps of Engineers' "Flood-Proofing Regulations," certified by a registered engineer or architect. Fully enclosed space below the lowest floor is banned outright; partially enclosed space used only for parking, access or storage must have at least two openings totaling one square inch per square foot of enclosed area, with the bottom of each opening no higher than one foot above grade (Section 305-24C).

Accessory structures under 200 square feet are exempt from elevation if they hold no utilities, sanitary facilities or human habitation, and historic structures can seek a documented exemption if compliance would strip their historic listing (Section 305-24D).