Feb 27 2007
As South Carolina moves to adopt the latest editions of the International Building Code (IBC) and the International Residential Code (IRC), proposed amendments to the 2006 IRC would allow some homes to be built below the minimum strengths prescribed in this national consensus standard.
According to the Institute for Business & Home Safety (IBHS), the result will be weaker homes that have a poorer ability to weather the force of windstorms and earthquakes.
At issue are two proposals that will be heard by the South Carolina Building Codes Council and voted on at a meeting in Columbia February 28. The first would remove the requirement that new homes be provided with window and door protection from flying debris in areas at greatest risk from hurricanes. Instead, it would allow homes to be designed for pressure that would build up as wind enters the home through broken windows or doors that burst open.
This change means the home would be unlikely to lose its roof or walls when a hurricane strikes, but the chance that a window or door will fail is greatly increased. A study of window failures in Florida following the recent hurricanes showed that about one third of homes without window protection in areas where gust winds exceeded 120 mph had at least one broken window.
According to IBHS, when that happens, wind and water blows through the home, ruining contents and interior features like walls, cabinetry and flooring, degrading the "safe shelter" value of a home and typically forcing homeowners to find temporary housing elsewhere. And if the power is out, residents would not be able to sufficiently dry out their homes, increasing the threat of mold growth.
IBHS notes that the 2006 IRC, which it says provides the best available current guidance on reducing loss of life and damage to structures in this and similar kinds of events, eliminated the option to design for internal pressure, and the American Society of Civil Engineers (ASCE) eliminated this option except for storage and agricultural buildings.
The second proposal has several parts. One change would allow houses built in areas with moderate seismic risk, such as Columbia, to be built with no consideration of that risk whatsoever. A second change would allow homes in places with the highest seismic risk, such as Charleston, which was identified by FEMA as one of the top ten urban areas most vulnerable to earthquake damage, to be built using methods intended for simple rectangular buildings in lower risk regions, rather than require them to be designed by an engineer as specified in the 2006 IRC.
"The I-Codes represent the latest consensus on seismic provisions and recommendations and should be followed in order to help reduce the magnitude and extent of damage and risk of injury that will occur when a large seismic event occurs," said Tim Reinhold, IBHS vice president and director of engineering. He points out that the maps of high risk areas in the Charleston area have been fine tuned to identify the areas with greatest risk and poor soils using local knowledge. Reinhold adds, "These are not just blanket national provisions that are out of touch with local conditions and risk.
"Any action that could potentially decrease a home's resistance to natural hazards below consensus minimum requirements defies reason. The South Carolina Building Codes Council should take this opportunity to adopt the latest consensus design provisions and ensure that new homes built in South Carolina are better able to withstand nature's forces," Reinhold says.
The Institute for Business & Home Safety works to reduce the social and economic effects of natural disasters and other property losses by conducting research and advocating improved construction, maintenance and preparation practices.