Guidelines On Flood Adaptation For Rehabilitating Historic Buildings

GUIDELINES FOR REHABILITATING HISTORIC BUILDINGSTHE SECRETARY OF THE INTERIOR’S STANDARDS FOR REHABILITATION (36 CFR PART 68)The Standards for Rehabilitation are codified in National Park Service regulations 36 CFR Part 68 and are regulatory only forprojects receiving Historic Preservation Fund grant assistance and other Federally-assisted projects. The Standards can beused to guide work on any historic building. A separate version of the Standards for Rehabilitation codified in 36 CFR Part67 is used for “certified historic structures” pursuant to the Federal Historic Preservation Tax Incentives Program.The following Standards (36 CFR Part 68) are to be applied to specific rehabilitation projects in a reasonable manner, takinginto consideration economic and technical feasibility, as well as the property’s significance, existing physical condition, andavailable documentation.1.A property will be used as it was historically or be given a new use that requires minimal change to its distinctivematerials, features, spaces and spatial relationships.2.The historic character of a property will be retained and preserved. The removal of distinctive materials or alterationof features, spaces and spatial relationships that characterize a property will be avoided.3.Each property will be recognized as a physical record of its time, place and use. Changes that create a false sense ofhistorical development, such as adding conjectural features or elements from other historic properties, will not beundertaken.4.Changes to a property that have acquired historic significance in their own right will be retained and preserved.5.Distinctive materials, features, finishes and construction techniques or examples of craftsmanship that characterizea property will be preserved.6.Deteriorated historic features will be repaired rather than replaced. Where the severity of deterioration requiresreplacement of a distinctive feature, the new feature will match the old in design, color, texture and, where possible,materials. Replacement of missing features will be substantiated by documentary and physical evidence.7.Chemical or physical treatments, if appropriate, will be undertaken using the gentlest means possible. Treatmentsthat cause damage to historic materials will not be used.8.Archeological resources will be protected and preserved in place. If such resources must be disturbed, mitigationmeasures will be undertaken.9.New additions, exterior alterations or related new construction will not destroy historic materials, features and spatialrelationships that characterize the property. The new work will be differentiated from the old and will be compatiblewith the historic materials, features, size, scale and proportion, and massing to protect the integrity of the propertyand its environment.10. New additions and adjacent or related new construction will be undertaken in such a manner that, if removed in thefuture, the essential form and integrity of the historic property and its environment would be unimpaired.5GUIDELINES ON FLOOD ADAPTATION FOR REHABILITATING HISTORIC BUILDINGS

THE SECRETARY OF THE INTERIOR’S STANDARDS FOR REHABILITATIONTHE SECRETARY OF THE INTERIOR’S STANDARDS FOR REHABILITATIONINTRODUCTION TO THE STANDARDSThe Secretary of the Interior acting through the NationalPark Service is responsible for establishing standards forall cultural resources programs and for advising Federalagencies on the preservation of historic properties listedin or eligible for listing in the National Register of HistoricPlaces, including National Historic Landmarks. In partialfulfillment of this responsibility, The Secretary of theInterior’s Standards for the Treatment of Historic Propertieshave been developed to guide work undertaken on historicproperties; there are separate standards for preservation,rehabilitation, restoration, and reconstruction.Preservation Tax Incentive purposes. They have also beenwidely adopted and used by local historic district andplanning commissions, local governments, non-profitorganizations, design and building professionals, and thegeneral public.The intent of the Standards is to assist in the long-termpreservation of the historic character of a property throughthe retention of its historic materials, features, and spaces.The Standards pertain to historic buildings of all materials,construction types, sizes, and occupancies and addressboth the exterior and the interior of the building. TheyThe Secretary of the Interior’s Standards for Rehabilitation also encompass a building’s site and setting, includingare one of the four sets of standards that comprise the landscape features as well as attached, adjacent, or relatedoverall treatment standards and address the most prevalent new construction.treatment. “Rehabilitation” is defined as the act or processof making possible a compatible use for a property throughrepair, alterations, and additions while preserving thoseportions or features which convey its historic, cultural, orarchitectural values.The treatment standards were developed by the Secretary ofthe Interior to determine the appropriateness of proposedwork on historic properties. The Standards for Rehabilitationguide Federal agencies in carrying out their responsibilitiesfor historic properties in Federal ownership or control andare used by state and local officials in reviewing both Federaland non-Federal rehabilitation proposals. In addition, theStandards are used to determine if a rehabilitation projectqualifies as a “certified rehabilitation” for Federal HistoricGUIDELINES ON FLOOD ADAPTATION FOR REHABILITATING HISTORIC BUILDINGS6

GUIDELINES FOR REHABILITATING HISTORIC BUILDINGS[6] Flood waters can also damage interior spaces. This historic home in Bay St. Louis, MS, was severely impacted by the storm surge from Hurricane Katrina. Evenwith such dramatic damage, it is crucial to properly assess the condition of historic materials and identify what remains and can be retained. In this case, most of thewoodwork, the wood wainscot, upper sections of plaster in some rooms, and some areas of flooring were cleaned, dried, and repaired. Photo: Mississippi Departmentof Archives and History, Mississippi Historic Resources Inventory (HRI) Database. http://www.apps.mdah.ms.gov/Public7GUIDELINES ON FLOOD ADAPTATION FOR REHABILITATING HISTORIC BUILDINGS

GUIDELINES FOR REHABILITATING HISTORIC BUILDINGSGUIDELINES FOR REHABILITATING HISTORIC BUILDINGSINTRODUCTION TO THE GUIDELINESThe Standards for Rehabilitation are a series of ten principalsabout maintaining and preserving the historic characterand features of a historic property. Guidelines give moredetailed, best- practice advice to apply the Standards duringproject planning by providing general design and technicalrecommendations. Unlike the Standards, guidelines arenot codified as program requirements. The Guidelines forRehabilitating Historic Buildings issued in 2017 should beconsulted along with any topic-specific guidelines.MASONRY: STONE, BRICK, TERRA COTTA, CONCRETE, ADOBE, STUCCO, AND MORTARRECOMMENDEDRepairing masonry walls and other masonryRemoving non-deteriorated mortar from soundfeatures by repointing the mortar jointsjoints and then repointing the entire buildingwhere there is evidence of deterioration, suchto achieve a more uniform appearance.as disintegrating mortar, cracks in mortarjoints, loose bricks, or damaged plaster on theinterior.maRemoving deteriorated lime mortar carefullyby hand raking the joints to avoid damagingGuidelines are presented in a “Recommended” vs. “NotRecommended” format. Those approaches, treatments,and techniques that are consistent with the Standards forRehabilitation are listed in the “Recommended” columnon the left; those approaches, treatments, and techniqueswhich could adversely affect a building’s historic characterare listed in the “Not Recommended” column on the right.These Guidelines are intended to be used in the context ofrehabilitating historic buildings and include sections ona building’s site and setting. They are not meant to fullyaddress the treatment of cultural landscapes, archeologicalresources, historic districts, and other types of historicresources.elNOT RECOMMENDEDthe masonry.xpUsing power tools only on horizontal jointsAllowing unskilled workers to use masonryon brick masonry in conjunction with handsaws or mechanical tools to removechiseling to remove hard mortar that isdeteriorated mortar from joints prior todeteriorated or that is a non-historic materialrepointing.Ewhich is causing damage to the masonryunits. Mechanical tools should be used only byskilled masons in limited circumstances andgenerally not on short, vertical joints in brickmasonry.Example of “Recommended” and “Not Recommended” format from the 2017 Guidelines forRehabilitating Historic Buildings, page 84.GUIDELINES ON FLOOD ADAPTATION FOR REHABILITATING HISTORIC BUILDINGS8

GUIDELINES FOR REHABILITATING HISTORIC BUILDINGSUSING THE GUIDELINES ON FLOOD ADAPTATIONUnlike other versions of the Guidelines, which are organizedprincipally by material or building feature, the Guidelineson Flood Adaptation for Rehabilitating Historic Buildingsare organized by flood adaptation measures. The mostcommon treatments undertaken to create more resilientproperties have been included in these Guidelines andare described using definitions provided by the FederalEmergency Management Agency (FEMA). The adaptationtreatments are: Planning and Assessment for Flood Risk Reduction Temporary Protective Measures Site and Landscape Adaptations Protect Utilities Dry Floodproofing Wet Floodproofing Fill the Basement Elevate the Building on a New Foundation Elevate the Interior Structure Abandon the Lowest Floor Move the Historic Building9GUIDELINES ON FLOOD ADAPTATION FOR REHABILITATING HISTORIC BUILDINGSThe “Planning and Assessment for Flood Risk Reduction”section should be completed for all projects prior toselecting an adaptation treatment. While “TemporaryProtective Measures” and “Protect Utilities” are treatmentsthat generally result in minimal changes to a building, thetreatment approaches are not organized in a particularorder. The impacts of the other adaptation treatments to thehistoric building will vary greatly depending on multiplefactors such as location and site conditions of a property,historic significance, flood risk, physical and structuralattributes, and its features, materials, and architectural style.For example, elevating a building on a new foundation mayhave a minimal impact on one building’s historic character,yet for another property the same treatment may changethe building’s historic character significantly and not meetthe Standards for Rehabilitation. Selecting more than onetreatment or combining treatment approaches may benecessary to make the building more resilient to floodingand/or to minimize the impacts to the historic characterand appearance of the property.

GUIDELINES FOR REHABILITATING HISTORIC BUILDINGSThe Guidelines on Flood Adaptation for RehabilitatingHistoric Buildings are general and intended to provideguidance in interpreting and applying the Standards torehabilitation projects involving buildings that are at a riskfor flooding. They are not meant to give case-specific advice.They cannot tell property owners or developers whichfeatures of a historic building are important in defining itshistoric character and, therefore, must be retained. (SeePreservation Brief 17: Architectural Character – Identifyingthe Visual Aspects of Historic Buildings as an Aid to Preservingtheir Character.) This case-by-case determination is bestaccomplished with the assistance of qualified historicpreservation professionals in the very early stages of projectplanning. For any treatment undertaken, assemble theappropriate project team, including experienced architects,engineers, and other professionals. Obtain any necessaryapprovals or certifications prior to beginning work onthe project.Achieving greater resilience and reducing flood risk mustbe balanced with economic and technical feasibility whileminimizing the impacts to the historic character of thebuilding. These Guidelines are designed to help identify andevaluate the different adaptation options in order to selecta treatment that meets the Standards for Rehabilitation.Wherever possible, the Guidelines provide “Recommended”methods of implementing each type of adaptation in order topreserve as much of the historic character of a building andits site and setting as possible. All of the “Recommended”treatments may not apply to every project. Technicallimitations are identified for each treatment.These Guidelines do not address disaster response or shortterm recovery. The Guidelines may be used after a floodevent as properties undergo rehabilitation and adaptationto address the damage and future flooding risk. Limitedinformation about drying and cleaning after a flood isincluded with Wet Floodproofing because it is an integralpart of that adaptation.[7] Technical and economic limitations must be considered when attempting to reduceflood risk and create greater resilience; changes must also respect the historic characterof the property. This can be a challenging balance for a project to achieve.GUIDELINES ON FLOOD ADAPTATION FOR REHABILITATING HISTORIC BUILDINGS10

GUIDELINES FOR REHABILITATING HISTORIC BUILDINGS"The Guidelines onFlood Adaptationfor RehabilitatingHistoric Buildingsshould only beapplied to historicproperties withan establishedrisk of flooding."The Guidelines on Flood Adaptation for RehabilitatingHistoric Buildings should only be applied to historicproperties with an established risk of flooding. Thisrisk can be determined by quantifiable and/or sciencebased projections or a community model or projection forflood risk areas. Such maps and models take into accountriver flow, storm tides, hydraulic analysis, rainfall, andtopographic surveys among other factors.Finally, the Guidelines address unconventional treatmentsand situations when a historic building may not be able toA project meets the Standards when the overall effect of all be retained and preserved. Demolition is not a treatmentwork is consistent with the property’s historic character. that meets the Standards for Rehabilitation. These twoTreatments that might not be considered in other sections are included solely for informational purposes.rehabilitation contexts because of their impacts on thehistoric character of a property may be acceptable in thecontext of adapting the property to flooding hazards.Even in this context, the selected treatment should alwaysbe one that minimizes the changes to the building’shistoric character and appearance while addressing therisk. Adaptation treatments should increase the building’sresilience to flooding risks as much as possible, but shoulddo so without destroying significant historic materials,features, or spaces.The entire scope of the project, including alterationsrelated to flood adaptation as well as any other work tothe building or site, must be evaluated. The amount ofchange to features and spaces that can be accepted withinthe Standards will vary according to the roles they play inestablishing the character of the property.11Aspects less critical to the historic character may be alteredmore substantially with less effect on the character of thebuilding as a whole. However, the cumulative effect ofchanges that are numerous or substantial can in someinstances alter the overall character of the building, in whichcase the rehabilitation project will not meet the Standards.GUIDELINES ON FLOOD ADAPTATION FOR REHABILITATING HISTORIC BUILDINGS"Treatments that might notbe considered in otherrehabilitation contextsbecause of their impacts onthe historic character of aproperty may be acceptablein the context of adapting theproperty to flooding hazards."

GUIDELINES FOR REHABILITATING HISTORIC BUILDINGSASSESSING THE RISK ANDSELECTING AN ADAPTATION TREATMENTBefore undertaking any work to adapt a historic buildingto be more resilient to potential flooding, research aboutthe actual flood risk as well as about the historic propertymust be undertaken. Proposed alterations to the propertywill need to be adequate to address the identified risk.Property owners should take into account the characteristicsof the potential flood. These characteristics include thedirection the water will likely flow, the expected speed anddepth of the water, the duration of the flood, whether therewill be wave action, the potential for water-borne debris,the water salinity, and contamination of the flood waters.The applicable Federal, state, and local code requirementsand regulations must also be considered.[8] Understanding the characteristics of a flood are critical to understandingproperty risk. Significant structural damage occurred to this building as aresult of a riverine flood in Cedar Rapids, IA, in 2008.Photo: Greg Januska[9] Fast-moving flood waters can undermine a foundation or scour outland around a building. The Little Church of the Pines in Salina, CO, wasleft structurally compromised after heavy rains caused flooding in theFront Range of the Rocky Mountains in 2013. Photo: Burton Constructionburton-construction.comGUIDELINES ON FLOOD ADAPTATION FOR REHABILITATING HISTORIC BUILDINGS12

GUIDELINES FOR REHABILITATING HISTORIC BUILDINGS"Established floodrisk level" describesthe property-specificheight of anticipatedfloodwater."These guidelines use the term “established flood risklevel” to describe the property-specific height of anticipatedfloodwater. This measurement should be based uponrecognized flood data, past flood events, site-specificreports, and other applicable information. Often this heightis dictated by local floodplain ordinances and codes andcan be higher than the predicted flood level. In order toremain more general, this document purposefully doesnot use terms for flood risk defined by other agencies. Theuse of “established flood risk level” is an attempt to avoidconfusion and the appearance of providing interpretationof Federal, state, and local regulatory terms for flood risk.Prior to planning or undertaking any work, the spaces,features, materials, and finishes of the historic propertyaffected by the flooding or the proposed adaptive treatmentshould be documented. The property’s existing capacity tosustain and recover from flooding, as well as its physicalcondition and use, should be evaluated. Those spaces,features, and materials that are important to the historiccharacter and significance of the property should be identifiedfor retention and preservation. Existing materials and featuresthat provide additional resiliency to flooding may also beconsidered for retention, improvement, or enhancement.In regions where buildings were historically adapted tofrequent flooding, traditional treatment approaches shouldbe considered.It may also be helpful to consider adapting a historic propertyin scalable phases, particularly for coastal properties at riskfrom rising sea levels and increasing flood risk. Where themagnitude and time horizon of the risk are uncertain, it isimportant to build in future capacity where economicallyand technically feasible – for example, a flood wall with an13GUIDELINES ON FLOOD ADAPTATION FOR REHABILITATING HISTORIC BUILDINGS[10] The Great Johnstown Flood of 1889, caused by a catastrophic damfailure, shows the extent of damage that can occur from a large-scale,fast-moving flood event. Whole buildings were destroyed, others wereshifted from their foundations, and massive amounts of debris causedconsiderable loss of life, damage, and destruction. Photo: NPS[11] Flood forces are powerful and can result in a building being shiftedfrom its foundation. This historic property in Gulfport, MS, was knockedoff of its piers by Hurricane Katrina in 2005. Photo: Jennifer V.O. Baughn/Mississippi Department of Archives and History, January 26, 2006

GUIDELINES FOR REHABILITATING HISTORIC BUILDINGSover-engineered foundation that can be extended higherin the future.These Guidelines are intended to assist property ownersundertaking a flooding adaptation project, recognizingthat, as with any rehabilitation project, there are alwaysother design, programmatic, financial, and regulatoryrequirements that must also be considered in planningsuch projects. Among these, the National Flood InsuranceProgram (NFIP) may have significant financial impacts andinfluence design decisions.

The Guidelines on Flood Adaptation should be used in conjunction with the Guidelines for Rehabilitating Historic Buildings that are part of The Secretary of the Interior's Standards for the Treatment of Historic Properties with Guidelines for Preserving, Rehabilitating, Restoring & Reconstructing Historic Buildings, issued in 2017. Like the