47.5 MB - The Whole Building Design Guide

pressure, hydrodynamic loads, wave loads,and debris impact loads). Exterior walls mustalso be designed to prevent infiltration andseepage of water, whether through the wallitself or through any openings, includingwhere utility lines penetrate the envelope.Floodproofed buildings constructed onpermeable soils require additional designattention, because they are susceptible to hydrostaticpressure from below.According to the NFIP regulations, nonresidentialbuildings and nonresidentialportions of mixed-use buildings may be dryfloodproofed. Areas used for living andsleeping purposes in health care facilitiesand dormitory rooms at fire stations maynot be dry floodproofed. Although floodproofingof the nonresidential spaces isallowed, careful consideration must be given to the possible riskto occupants and additional physical damage.All flood protection measures are designed for certain flood conditions.Therefore, there is some probability that the design willbe exceeded (i.e., water will rise higher than accounted for in thedesign). When this happens to a dry floodproofed building, theconsequences can be catastrophic. As a general rule, dry floodproofingis a poor choice for new critical facilities when avoidanceof the floodplain or elevation methods to raise the building abovethe flood level can be applied. Floodproofing may be acceptablefor retrofitting existing buildings under certain circumstances (seeSection 2.4.4).A number of dry floodproofing limitations and requirements arespecified in ASCE 24:m Dry floodproofing is limited to areas where flood velocities atthe site are less than or equal to 5 feet per second.m If human intervention is proposed, such as measures toprotect doors and windows, the flood warning time shall be aminimum of 12 hours unless the community operates a floodCommunities that participate in the NFIPwill require that a registered professionalengineer or architect develop or review thestructural design, specifications, and plans,and certify that the dry floodproofingdesign and methods of construction to beused are in accordance with acceptedstandards of practice. The standards ofpractice require that the building, togetherwith attendant utility and sanitary facilities,be designed so that it is watertight, withwalls substantially impermeable to thepassage of water and with structuralcomponents having the capability ofresisting hydrostatic and hydrodynamicloads and effects of buoyancy associatedwith the design flood event.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-65