Coastal communities across the country are breathing sighs of relief following the relatively mild 2006 hurricane season, considering 2005 produced a record-breaking 27 named tropical storms including 15 hurricanes. Of those, four reached Category 5 strength. The areas devastated in 2005, especially by Hurricanes Katrina and Rita, are still rebuilding.
The effects of Katrina and Rita will be with Louisiana and other Gulf Coast states for a generation or more. The good news is hurricane recovery represents an opportunity to improve the quality of life for thousands of families. They need support from all of us to achieve a better quality of life. And as we rebuild, we must do it right.
Louisiana took an important step to help prevent future hurricane damage by adopting the International Codes to guide reconstruction. The wind and flood provisions of the 2003 International Building Code and 2003 International Residential Code have been adopted for the parishes declared federal disaster areas following Katrina and Rita. Statewide adoption of the 2006 IBC, IRC and the 2006 International Existing Building, Fuel Gas and Mechanical Codes took effect Jan. 1, 2007.
Mississippi also responded to Katrina and Rita by forming a State Building Codes Council and requiring Mississippi’s five coastal counties to adopt the wind and flood provisions of the 2003 IBC and IRC. The council also chose the 2003 IBC and IRC as codes that may be adopted when jurisdictions choose to adopt building codes.
Alabama created a Building Code Study Commission to evaluate the need for statewide building codes and the procedure for implementation.
The International Code Council is assisting Gulf Coast recovery through education and outreach. Many of these communities never had building codes before Katrina and Rita. As Louisiana was adopting the I-Codes, the ICC established a regional office in the state, and staff is assisting jurisdictions with code adoptions and conducting training and offering new certifications to support building officials and inspectors.
To see a chart detailing major changes in building codes, click here.
Builders must make a commitment as well. They know the value of a disaster-resistant home and that techniques and materials can strengthen homes. Building codes should not be looked at as a burden. The codes are in place to protect builders and their clients. Learning and following code requirements comes with the reward of better protection of our nation’s coastal residents.
How Damage Happens
Once wind speeds reach 74 mph, a storm is officially classified as a hurricane. The combined effects of water and wind must be addressed if buildings are to perform satisfactorily in hurricane-prone areas.
Water affects the building by the force of waves and flooding. Buildings should be connected to the foundation system with proper connections, and elevated above flood levels. Because of the potential of wave action, buildings should be elevated above the crest of the wave. Piles and other foundation systems should be designed to resist the impact of waves.
Wind produces forces on buildings depending on its relationships to wind direction. Wind blowing against a wall facing the wind (windward) will cause inward-acting (pushing) pressure on the wall and outward-acting (pulling) pressures on the opposite (leeward) and side walls. Wind flowing around the corners, changing directions, causes turbulence that creates high localized outward pressures. Each side of the building must be designed for wind from any direction.
Wind acting on the roof may cause outward pressure or a combination of inward or outward pressure depending on wind and roof slope. As the wind flows over the roof, uplift occurs; the faster the wind, the greater the uplift. Wind blowing in a direction perpendicular to the ridge of a high-sloped roof will cause inward pressure on the windward side of the roof and outward pressure on the leeward side. Wind blowing parallel to the ridge will result in outward pressures on the roof surfaces. Winds flowing around eaves, ridges and overhangs cause high uplift forces.
Damage to these components is common during high winds.
Should windows or doors fail, wind will gain entrance to a building and pressure changes will occur inside. Failure of an opening in the windward wall will cause the pressure inside to increase.
Lack of attention to connections may create a weak link in the load path, resulting in partial or total building failure. The proper design, construction and connection of all building components is essential to prevent damage.
What the Code Says
Detached one- and two-family dwellings constructed in accordance with the 2006 IRC results in a system that provides a complete load path that meets requirements for the transfer of loads from their point of origin through the load-resisting elements to the foundation. The IRC contains prescriptive requirements for residential construction that are within the scope of the design criteria specified in the code.
The code is applicable for construction in regions where the basic wind speeds are less than 100 mph in hurricane-prone regions or less than 110 mph elsewhere. Buildings located in areas with wind speeds greater than those specified must be designed in accordance with standards listed in the code. Engineered design in accordance with the IBC is permitted.
The code addresses wind-borne debris, methods of wall bracing, roof tie-downs and roof assemblies. In the space that follows, some of the ways codes address these issues are addressed. However, this should not be considered a comprehensive list of code requirements.
- Windows in buildings located in wind-borne debris regions must be protected with the use of impact-resistant glazing or shutters.
- The amount of wall bracing is based on the wind speed, number of stories and type of bracing used.
- Rafters and trusses must be attached to their supporting wall assemblies by connections capable of providing the required resistance.
- Asphalt shingles classified using ASTM D 3161 are acceptable for wind speeds less than 110 mph but must be classified using ASTM D 3161, Class F, for wind speeds greater than 110 mph. For normal application, asphalt shingles must be secured to the roof with not less than four fasteners per strip shingle or two fasteners per individual shingle. Where the wind speed is 110 mph or greater, special fastening methods are required.
- Underlayment in areas where the wind speed is greater than 110 mph must be applied in accordance with manufacturer’s instructions.
Addressing Flooding Issues
There are additional code requirements for buildings located within a flood hazard area. Buildings in a local flood hazard map must be designed in accordance with the following:
- Lowest portion of all structural members supporting the lowest floor must be located above the design flood elevation.
- The building must be designed, connected and anchored to resist flotation, collapse or permanent lateral movement due to loads from flooding equal to the design flood elevation.
- Mechanical and electrical systems must be above the design flood elevation.
- Water supply and sanitary sewage systems must be designed to minimize or eliminate infiltration of flood waters into the system.
- Construction must be by methods and practices that minimize flood damage.
One of the referenced standards in the IRC is the Standard for Hurricane Resistant Residential Construction (SSTD 10). The standard specifies prescriptive methods to provide wind-resistant design and construction detail for residential buildings in high-wind regions. This standard is being updated and will become the first edition of the ICC-600 Standard for Residential Construction in High Wind Regions. The standard was published for public comment in November 2006. Once the public comments are addressed, the standard will be submitted to ANSI for certification and should be available in June 2007.
The ICC-600 will provide a contemporary set of prescriptive requirements that supplement the IRC. These requirements, based on the latest engineering knowledge, are specific to high-wind regions and are intended to provide minimum requirements to improve the structural integrity of buildings and improve building envelope performance.
Building codes are important tools for mitigating potential damages from hurricanes. When properly applied and enforced, building codes are the solution. It must be emphasized that codes make buildings hurricane-resistant, not hurricane-proof. While building to newer codes may result in slight increases in construction costs, studies show that every dollar spent on building safer and stronger prevents four to seven dollars in future losses. Any building in which appropriate design and construction techniques have been correctly applied should be considered affordable.
We know that disaster will strike again and the steps we take today will make us better prepared for future disasters. Stronger codes — codes that are followed and enforced — will promote prosperity. It takes a massive effort, but if we all stand by our commitments, we will build a safer and more disaster-resistant country. In the final analysis, there can be little doubt that greater numbers of homes will survive future hurricanes if the latest technical knowledge is applied.