Mitigation Design Standards & Guidelines

Natural Hazards and Sustainability for Residential Buildings (2010)

FEMA P-798 examines current green building rating systems in a broader context. It identifies green building practices—the tools of today’s green building rating systems—that are different from historical residential building practices and that, unless implemented with an understanding of their interactions with the rest of the structure, have the potential to compromise a building’s resistance to natural hazard events.

This document discusses how to retain or improve natural hazard resistance while incorporating these green building practices. While most common green building practices provide sustainability advantages with little or no effect on structural performance or durability, others require reevaluation of the building’s structural design or detailing to retain its integrity during natural hazard events. Often, only minimal design modifications are required to maintain natural hazard resistance.

Download the Natural Hazards and Sustainability for Residential Buildings.



Engineering Data Fact Sheet

While the project type determines the specific engineering data requirements, typical engineering data needed is included in this fact sheet and divided into a variety of project types.  The Fact sheet outlines Drainage projects, Elevation projects, Building elevations and Wind retrofit projects.   Link to the Engineering Data Fact Sheet.

While the project type determines the specific engineering data requirements, typical engineering data needed is included in this fact sheet and divided into a variety of project types.  The Fact sheet outlines Drainage projects, Elevation projects, Building elevations and Wind retrofit projects.   Link to the Engineering Data Fact Sheet.


 


FLOOD DESIGN AND PLANNING CONSIDERATIONS


Highlights of ASCE 24 Flood Resistant Design and Construction

ASCE 24-14:  The American Society of Civil Engineers (ASCE) 24-14 is a referenced standard in the 2015 International Building Code® (IBC) and the 2015 International Residential Code® (IRC). Building and structures within the scope of the IBC proposed to be constructed in flood hazard areas must be designed in accordance with ASCE 24-14. The IRC requires dwellings in floodways to be designed in accordance with ASCE 24-14 and includes an alternative that allows communities to require homes in any flood zone to be designed in accordance with ASCE 24-15. Highlights of ASCE 24-14 that complement the NFIP minimum requirements include: Building Performance; Flood-Damage Resistant Materials; Utilities and Service Equipment and Siting Considerations.

ASCE 24-05:  The American Society of Civil Engineers (ASCE) 24-05 is a referenced standard in the International Building Code® and International Residential Code® (editions published 2012, 2009 and 2006).  Building and structures within the scope of the IBC proposed to be constructed in a flood hazard area must designed in accordance with ASCE 24. The IRC requires that dwellings in floodways to be designed in accordance with ASCE 24, and the 2012 and 2009 editions include an alternative that allows communities to require homes in Zones V to be designed in accordance with ASCE 24. Highlights of ASCE 24 that complement the NFIP minimum requirements include: Building Performance; Flood-Damage Resistant Materials; Utilities and Service Equipment; and Siting Considerations.

Link to the highlights on FEMA’s webpage.

 


Building Codes for Mitigation: Using ASCE 24 – Webinar

January 25, 2018

The Hazard Mitigation Assistance (HMA) Program provides assistance for mitigation activities that reduce damage and protect life and property from future damages.  HMA Addendum (dated 2/27/2015) states: “FEMA will use ASCE 24-14, or latest edition, or its equivalent as the minimum design criteria for all HMA-funded structure elevation, dry flood proofing, and mitigation reconstruction projects in flood hazard areas.”

FEMA’s Hazard Mitigation Assistance (HMA) Division delivered a webinar to share information on the American Society of Civil Engineers (ASCE) 24 Building Codes for Mitigation.  Presenters provided information on ASCE 24 flood-specific building code requirements as they relate to HMA, including information about mitigation projects such as elevations, floodproofing, and mitigation reconstruction. Participants who would find value in this webinar include floodplain administrators, city and building code officials, insurance adjusters, and others who have an interest in understanding and applying ASCE 24 requirements.

Participants who would find value in this webinar include floodplain administrators, city and building code officials, insurance adjusters, and others who have an interest in understanding and applying ASCE 24 requirements. Link to the Webinar:

Link to Q&A Sheet: FEMA HMA Webinar – Using ASCE 24 for Hazard Mitigation Assistance

Link to https://www.fema.gov/media-library/assets/documents/158814 for more information.

 


Guidance for Applying ASCE 24 Engineering Standards to HMA Flood Retrofitting and Reconstruction Projects

November 2013

This ASCE 24 HMA Guidance was prepared by the FEMA to assist local governments, designers, and property owners.  It identifies key design and construction requirements in the ASCE Structural Engineering Institute’s ASCE/SEI 24-05, Flood-Resistant Design, and Construction (ASCE 24) that apply to HMA flood mitigation grant projects.  

This document is in no way intended to be used in place of ASCE 24 but rather as a companion to the standard.  Designers, local officials, and others who want to apply the standard still need to refer to the standard for complete requirements.

The guidance does not advocate construction in the floodplain; rather, it is intended to reduce hazard risk for situations in which there is no practicable alternative.  The emphasis of this document is on mitigation if construction in the floodplain is not avoidable, although the best way to greatly reduce (if not eliminate) flood risk is to relocate a structure out of the floodplain.  The term “must” is used in the context of the ASCE 24 design standard to indicate compliance to applicable criteria within ASCE 24.

 


 

Minimum Design Standards for HMA Projects in Flood Hazard Areas

FEMA will use the American Society of Civil Engineers (ASCE) Flood Resistant Design and Construction or its equivalent as the minimum design criteria for all HMA funded structure elevation, dry floodproofing, and mitigation reconstruction projects in flood hazard areas. 

Flood Resistant Design and Construction, ASCE/SEI 24-14, provides minimum requirements for design and construction of structures located in flood hazard areas and subject to building code requirements. Identification of flood prone structures is based on flood hazard maps, studies, and other public information. This standard applies to new structures, including subsequent work, and to work classified as substantial improvement of existing structures that are not historic. Standard ASCE/SEI 24-14 introduces a new concept, Flood Design Class, that bases requirements for a structure on the risk associated with unacceptable performance.

The standard includes requirements for the following: basic siting and design and construction requirements for structures in flood hazard areas; minimum elevations for the lowest floor, flood damage-resistant materials, and floodproofing measures, each tied to a structure’s Flood Design Class; structures in high risk flood hazard areas subject to flooding associated with alluvial fans, flash floods, mudslides, erosion, high velocity flow, coastal wave action, or ice jams and debris; flood damage-resistant materials; dry floodproofing and wet floodproofing; attendant utilities and equipment, including electrical service, plumbing systems, mechanical/HVAC systems, and elevators; building access; and miscellaneous construction, including decks and porches, concrete slabs, garages and carports, accessory storage structures, chimneys and fireplaces, pools, and tanks. A detailed commentary containing explanatory and supplementary information to assist users of the standard is included for each chapter.

Standard ASCE/SEI 24-14 updates and replaces the previous Standard, ASCE/SEI 24-05. It provides essential guidance on design and construction to structural engineers, design professionals, code officials, floodplain managers, and building owners. The standard is adopted by reference in model building codes.

 

 


Engineering Principles and Practices for Retrofitting Flood-Prone Residential Structures 

January 1, 2012

The third edition of Engineering Principles and Practices is intended to further aid homeowners in selecting and successfully executing a flood retrofit on their home.  Engineering design and economic guidance on what constitutes feasible and cost-effective retrofitting measures for flood-prone residential and non-residential structures are presented.  Elevation, relocation, dry floodproofing, wet floodproofing, and the use of levees and floodwalls to mitigate flood hazards are discussed.  This edition was updated to be more user-friendly and concise, the overall length of the publication has been shortened.

 


Subdivision Design and Flood Hazard Areas (PAS 584) 

October 31, 2016

Subdivision Design and Flood Hazard Areas was prepared by the American Planning Association (APA) in partnership with the Association of State Floodplain Managers (ASFPM), and it was supported through a cooperative agreement with FEMA.  This report demonstrates the intersection of sustainability, resilience, and climate change in light of changing flood hazards and how these concepts play out in subdivision design.  

The purpose of this report is end the cycle of build-damage-rebuild, and provide communities with sound guidance to bring subdivision design into line with the best of floodplain planning.  The report includes many best practices as well as six planning and design principles; standards for review, inspection, and maintenance; and nine recommendations to keep subdivisions safe from flooding.

 


Second-Story Conversion – Elevation Project Design Considerations for HMA Applicants

Elevation is a common mitigation method for structures that are at risk of flooding, and is an eligible mitigation project under the FEMA HMA Grant Programs.  Structure elevation activities generally involve physically raising an existing structure in accordance with the 2015 HMA Guidance, or latest edition, and the American Society of Civil Engineers (ASCE) standard Flood Resistant Design and Construction (ASCE 24-14), or latest edition. 

ASCE 24-14 includes elevation to the Base Flood Elevation [BFE] plus freeboard, or higher when required by FEMA, local ordinance, or building code.  Structure elevation may be achieved through a variety of methods, including elevating on continuous foundation walls; elevating on open foundations, such as piles, piers, posts, or columns; and elevating on fill.  There are situations, such as structures with a slab-on-grade foundation, where physically raising the building is not feasible or cost-effective.  FEMA conducted research to identify alternative flood mitigation methods to address these types of situations and published this information as recovery advisories.

The purpose of the  Second Story Conversion Elevation Fact Sheet is to identify project design considerations that should be taken into account when developing these types of HMA-funded elevation projects.

 

 


FEMA P-936, Floodproofing Non-Residential Buildings

The primary focus of the guidance document is on dry floodproofing technologies for non-residential buildings, but it also includes an overview of other techniques including wet floodproofing and the use of levees and floodwalls. The publication provides information about regulatory requirements, design considerations, and descriptions of floodproofing methods and equipment.

Key document features include:

1) Tools to assist the designer or building owner in determining the best floodproofing option for a particular building including a vulnerability checklist,

 2) Case studies providing examples of applied floodproofing techniques,

3) Equations for determining flood forces and loads,

4) A summary of results from recent dry floodproofing research and testing for new construction.

Link to Floodproofing
Non-Residential Buildings – https://www.fema.gov/sites/default/files/2020-07/fema_p-936_floodproofing_non-residential_buiildings_110618pdf.pdf

 


Dry Floodproofing – Planning and Design Considerations Recovery Advisory

April 2018

The purpose of this Recovery Advisory is to provide guidance on the design of dry floodproofing measures to reduce flood damage and limit interruption of building services.  This advisory incorporates observations made by the FEMA Mitigation Assessment Teams (MATs) in Texas and Florida after Hurricanes Harvey and Irma. 

It describes best design practices and successful implementation of dry floodproofing, as well as lessons learned from failures.  The information in this advisory is directed toward existing and new non-residential facilities. 

Download the Dry Floodproofing – Planning and Design Considerations.