Across the nation are standardized building codes. States on the east coast have taken those building codes and enhanced them for hurricane resistant structures. States on the west coast have taken those building codes and enhanced them for earthquake resistant structures. Unfortunately, Oklahoma did not even have a statewide standardized building code until 2009 and the current code does not even begin to address the construction of tornado resistant housing.
Oklahoman’s, including me, have always assumed that if a house was in the path of a tornado, it was history. Assume no more. Last week, Rep. Richard Morrisette and I co-sponsored an interim study on safe housing and building codes. The study was an eye opener. Dr. Chris Ramseyer, Ph.D., P.E., Director of the Fears Structural Engineering Laboratory at the University of Oklahoma spoke about the construction of high wind resistant homes; building codes and the benefits of retrofit.
Dr. Ramseyer’s concise and informative presentation detailed the science behind a tornadic type high wind event’s impact on the integrity of structures. Of course, it is unlikely that any wood frame structures would survive a direct hit from an EF4 or EF5 tornado, however, even in a wide tornado, the EF4 or EF5 winds are often isolated to a small part of the storm.
Perhaps the most alarming information that came out of Dr. Ramseyer’s demonstration showed that the root cause of destruction of most residential structures is either substandard garage doors or inadequate rafter anchoring. The most exciting thing that came out of the study was that these two key construction components could be corrected during construction for around $1,500 and both can be the subject of relatively inexpensive retrofits.
Dr. Ramseyer showed that even if a window is broken the wind through that window will likely not be sufficient to blow the roof off in anything less than an EF4 Tornado, however, that same wind will cause severe damage and often total destruction of a residence once a garage door is breached. He also showed that when a roof is properly clipped and a wind resistant garage door is in use, a house may only sustain EF1 or EF2 damage even if it is within 70 feet or less from a house that sustains EF5 damage and has no clips and a less substantial garage door.