47.5 MB - The Whole Building Design Guide

Under the regulations of the NFIP and FEMA guidance, it is notconsidered appropriate to grant such a variance.2.4.4 REPAIRS, RENOVATIONS, ANDUPGRADESEvery critical facility that is considered for upgrades and renovations,or that is being repaired after substantial damage from anycause, must be examined for structural integrity and stability todetermine compatibility with structural modifications that may berequired to achieve acceptable performance. When an existing facilityis located in a flood hazard area, that examination shouldinclude consideration of measures to resist flood damage and reducerisks.The model building codes and the regulations of the NFIP requirethat work constituting “substantial improvement” of anexisting building be in compliance with the flood-resistant provisionsof the code. Non-substantial improvements should take intoaccount measures to reduce future flood damage, such as thosedescribed in Section 2.4.8, and wet floodproofing measures thatallow water to enter the building to avoid structural damage, aswell as emergency measures (see Section 2.4.9).Additional information on rehabilitationof existing buildings is provided inFlood Proofing: How to Evaluate YourOptions (USACE, 1993), FloodproofingNon-Residential Structures (FEMA 102),Floodproofing—Requirements andCertification (FIA-TB-3), and EngineeringPrinciples and Practices for RetrofittingFlood-prone Buildings (FEMA 259,1995). Although written primarily forhomes, this last reference contains verydetailed checklists and worksheets thatcan be modified. They also provide someguidance for evaluating the costs andbenefits of various measures.Compliance with flood-resistant provisionsmeans the existing building must be elevatedor dry floodproofed. Both options can be difficultfor existing critical facilities, given thetypical use, size, and complexity of some ofthese buildings. Retrofit dry floodproofing(described in Section 2.4.5) is generally limitedto water depths of 3 feet or less, unlessthe structural capacity of the buildings havebeen assessed by a qualified design professionaland found to be capable of resistingthe anticipated loads.Elevating an existing building presents anentirely different set of challenges and alsorequires detailed structural engineeringanalyses. It involves the same equipment and2-82 MAKING CRITICAL FACILITIES SAFE FROM Flooding