Wind & Tornado and Snow Resources

Wind Mitigation Options

 

  • Install hurricane shutters to protect windows and glass doors. Gable end roofs are more susceptible to high wind than other roof types. If you have a gable end roof, add bracings to reinforce the roof.
  • Consider fastening the roof to the walls with hurricane straps.
  • Reinforce garage doors and double-entry doors to prevent failure under wind pressure. Garage doors can be reinforced with girts and by strengthening the glider wheel tracks. Double-entry doors can be reinforced with a heavy-duty dead bolt, adding slide bolts on one of the doors, and using longer hinge attachments on the door and frame.
  • Maintain your property. Anything from loose shingles to trees can become a windborne missile. The distance between your home and any tree should be greater than a full-grown tree’s height.
 

FEMA Releases Resources for the Wind Resistant Provisions of the 2021 International Codes

Tornado in Western Kentucky

November 2, 2021

The provisions of the International Codes aim to ensure that structures can adequately resist wind forces.  FEMA has contributed to the development of the International Codes since the first edition was published in 2000, up to and including the latest 2021 edition.

FEMA is pleased to announce three new resources that summarize the wind resistant provisions of the 2021 International Codes.  These documents provide guidance on the wind resistant provisions in the building codes for property owners, engineers, design professionals, building codes officials and the general public.

For more of FEMA’s wind resistant building code resources, visit: https://www.fema.gov/emergency-managers/risk-management/building-science/building-codes.

 


Building Science – High Winds Publications

FEMA Building Science has developed publications and guidance to assist communities in making their buildings more resilient against the impacts of high winds. It is recommended that communities located in areas prone to high winds follow the guidance provided by FEMA to increase the resilience of buildings and structures.

Following FEMA guidance results in less damages and keeps occupants safer during a high wind event. Along with increasing the resilience of buildings, it is important that communities at risk of tornados follow other FEMA recommendations such as creating safe rooms to ensure the safety of community members.

Link to FEMA’s High Wind Publications

 


FEMA Building Science Resources to Assist with Reconstruction After an Extreme-Wind Event

December 9, 2020

Tornado damage in Western Kentucky

FEMA has produced numerous publications detailing best practices for natural hazard mitigation associated with extreme-wind impacts.  This Fact Sheet summarizes a few of the readily available publications and resources that can be used by homeowners, as well as design and construction professionals, during reconstruction following extreme-wind events.

Link to the informative Fact Sheethttps://www.fema.gov/sites/default/files/documents/fema_building-science-resources-assist-reconstruction-after-extreme-wind-event.pdf

 


FEMA Releases the Updated Wind Retrofit Guide (FEMA P-804)

FEMA is pleased to announce the updated release of FEMA P-804, Wind Retrofit Guide for Residential Buildings in Hurricane-Prone Regions available at: https://www.fema.gov/emergency-managers/risk-management/building-science/publications.

FEMA P-804 summarizes the technical information needed for selecting and implementing cost-effective wind retrofit projects for existing one- and two-family dwellings in the hurricane-prone region of the US and its territories. The 2nd Edition of FEMA P-804 (last published in 2010) provides clarified and updated guidance based on lessons learned over the past 13 years of post-hurricane damage assessments and advances in wind engineering. Although this publication references guidance for one- and two-family dwellings in the hurricane-prone region, much of this guidance could also be applicable to non-coastal areas subject to high winds.

FEMA P-804 continues to present mitigation measures in three successive Mitigation Packages: Basic, Intermediate, and Advanced.

Key changes to FEMA P-804 include:

  • The Insurance Institute for Business & Home Safety (IBHS) 2020 FORTIFIED Home Standard (IBHS, 2020) is being used as a reference.
  • The FEMA P-804 Mitigation Package requirements have been updated to meet or exceed the criteria of the respective 2020 FORTIFIED HomeTM Hurricane designations for existing homes.
  • Any additional FEMA requirements which are more conservative than FORTIFIED 2020 will be noted to be “FEMA Grant Requirements.”

FEMA P-804 references the latest edition of ASCE 7, Minimum Design Loads and Associated Criteria for Buildings and Other Structures (ASCE/SEI 7-22) and the soon to be published 2024 model building codes from the International Code Council (expected summer 2024).

While this publication outlines minimum technical and performance-based grant requirements for wind retrofits, refer to the latest edition of FEMA’s Hazard Mitigation Assistance Program and Policy Guide (HMA Guide) for the most current FEMA policy statement on residential wind retrofit and HMA grants implementation requirements. See: https://www.fema.gov/grants/mitigation/hazard-mitigation-assistance-guidance

For more information on building science, visit fema.gov/building-science.


Overview of FEMA P-804 | Wind Retrofit Guide for Residential Buildings

May 31, 2019

Protecting your property from high winds can involve a variety of actions, from inspecting and maintaining your building to installing protective devices.  Most of these actions, especially those that affect the exterior shell of your building, should be carried out by qualified maintenance staff or professional contractors licensed to work in your state, county, or city.  For buildings with Exterior Insulation Finishing System (EIFS) walls, a type of wall often used for commercial buildings, one example of wind protection is inspecting and maintaining the walls.

Link to the two-page overview – Wind Retrofit Guide for Residential Buildings

 


Guidelines for Wind Vulnerability Assessments of Existing Critical Facilities

October 2019

FEMA’s Building Science Branch Releases Guidelines for Wind Vulnerability Assessments of Existing Critical Facilities, a manual for design professionals.

Hurricanes Irma and Maria in Puerto Rico and the U.S. Virgin Islands, as well as other recent storms including Hurricane Michael in Florida, resulted in extensive wind damage to critical facilities.  FEMA Building Science, Region II, and DR-4339, in coordination with partners and subject matter experts, has developed FEMA P-2062: Guidelines for Wind Vulnerability Assessments of Existing Critical Facilities. The manual incorporates observations and lessons learned from recent and past hurricanes, current building code requirements, and other historic high wind events.

The purpose of this manual is to provide design professionals with guidelines for assessing the vulnerability of critical facilities to wind pressure, wind-borne debris, and wind-driven rain.  The guidelines apply to critical facilities both within and outside hurricane-prone regions as well as to critical facilities in tornado-prone regions.

The results of an assessment can be used by building owners; design professionals; entities that award repair, reconstruction, or mitigation grants; as well as state, local, tribal, and territorial government agencies developing mitigation plans.

 


Asphalt Shingle Roofing for High-Wind Regions

May 2018

The purpose of this Recovery Advisory is to recommend practices for installing asphalt roof shingles that will enhance wind resistance in high-wind regions. For the purpose of this advisory, a high-wind region is considered to be an area where the basic (design) wind speed for Risk Category II buildings (as defined in American Society of Civil Engineers [ASCE] 7, Minimum Design Loads and Associated Criteria for Buildings and Other Structures) is greater than 115 miles per hour.

The primary audience for this advisory includes contractors and design professionals, but the practices presented here may also be helpful for homeowners and other building owners. 

Download the Asphalt Shingle Roofing for High-Wind Regions.

 


Snow Mitigation Options


FEMA P-957, Snow Load Safety Guide

The objective of the Risk Management Series Snow Load Safety Guide is to inform building stakeholders about the risks a snow event poses to their buildings, provide them with information about preventative measures to take before the snow season and inform them of actions that should be taken before, during, and after a snow event. This document is not intended to provide a comprehensive discussion of the underlying issues or forensics of snow-induced structural failure.

The purpose is instead to:

1. Inform building stakeholders of susceptible snow loading conditions

2. Identify potentially vulnerable roof framing systems

3. Outline a general methodology to monitor buildings for signs of potential failure so that steps can be taken to reduce the potential risk of snow-load-induced structural failure.

Link to Snow Load Safety Guide

Kentucky Ice Storm 2009


FEMA Roof Snowdrift Design Guide

Following a series of heavy snow and wind events in February of 2015, a FEMA team assessed four partial school building collapses in the Greater Boston area. In all four cases, the partial collapses were due to roof snowdrift loading. In two of the four cases, the FEMA team observed and documented 3-D drifts that cannot be determined when following the current ASCE 7 minimum load requirements.

This new design guide provides guidance, in the form of three design examples, for three-dimensional (3-D) roof snowdrifts. The procedures identified are consistent with the intersecting drift provisions expected in the 2022 edition of ASCE 7 and are intended to serve as best practice guidance for design professionals in the interim.

Link to FEMA Roof Snowdrift Design Guide

 

 


 

 

 

 

 

 

 

 

 

 

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