Both the NFIP and the major national building code organizations rely on the US Army Corps of Engineers (USACE) for floodproofing standards.

What Constitutes 'Floodproofing'?

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Katrina. FEMA News Photo.

What exactly do we mean when we “flood proof” a building?  FEMA has adopted the definition from the USACE publication “Flood Proofing Regulations.” This document states… 

“…that a substantially impermeable wall shall not permit the accumulation of more than 4 inches of water depth during a 24-hour period if there were no devices provided for its removal. However, sump pumps shall be required to control this seepage.” Flood resistant materials, described in Technical Bulletin 2, “Flood-Resistant Materials Requirements,” must be used in all areas where such seepage is likely to occur.”

The USACE Flood Proofing Regulations (see link to download a PDF copy) deals only with the treatment of hydrostatic and hydrodynamic forces and waterproofing associated with riverine flooding only. To the extent that coastline structures are subject to these semi-static conditions, these provisions will be applicable to coastal or tidal flooding situations; however, no consideration is given to the special problems of wave impact, corrosion, and erosion associated describe the imagewith coastal flooding.

Presray's standards are far more stringent than the mininum standards set forth by the USACE regulations. Beware of FEMA or USACE "Certification" claims because 4 inches of water in a large building over a 24-hour period can be a lot of water!