DAS Exclusive: First-Ever Study Praises Garage Doors in Hurricane
© 2005 Door & Access Systems
Publish Date: Fall 2005
Authors: Tim Reinhold, Jeff Burton, Joe Hetzel
First-Ever Study Praises Garage Doors in Hurricane
“The report is a selling point for garage door manufacturers. The data show that the product did exactly what it was supposed to do. The evidence doesn’t lie. The newer code-compliant garage doors are protecting homes, lives, and lifestyles.”
– Jeff Burton, IBHS
Editor’s Note: This exclusive report is a landmark study for our industry. Reasons:
(1) It is the first time that extensive computerized data (from building permits) have been used to demonstrate garage door performance.
(2) The study provides abundant statistical evidence that newer (code-compliant) garage doors performed extremely well in a Category 4 hurricane.
(3) DASMA holds the distinction of being the first product association to participate in such a study. In this way, our industry leads all other building products (e.g., roofing, siding, windows, entry doors, etc.) in demonstrating proactive concern for product performance.
The following report is an edited and condensed version of the full study, which itself is part of a larger IBHS study. For a free copy of the full 13-page garage door report, contact Jeff Burton at Jburton@IBHS.org.
Hurricane Charley: Garage Door Permit Study
By Dr. Timothy Reinhold, P.E., and Jeff Burton, a Certified Building Official, both with the Institute for Business & Home Safety (IBHS), and Joe Hetzel, P.E., of DASMA
The research focused on the damage caused by Hurricane Charley, which hit Charlotte County, Fla., on Aug. 13, 2004. Of the four storms to strike Florida that summer, Charley was the only hurricane with wind speeds that exceeded the maximum expectations of the 2001 Florida Building Code.
Charlotte County, unlike many other counties, provides the advantage of having records of building permits that mention new garage doors. This investigation focused on garage doors because previous studies have indicated that garage door failures can precipitate roof failure and major damage to the home. The goal was to determine the correlation between garage door replacement and the age of the doors that were replaced.
2,084 Garage Door Permits
The building permits indicated the year when each door was originally installed. The year of installation then revealed which building code was in effect at that time. The study focused on single-family homes built from 1980 until Charley’s landfall in August 2004. All homes in the study had garage doors. Over the course of those 25 years, six different building codes have been in effect: the Standard Building Code (SBC) of 1976, 1988, 1991, 1994, 1997, and the Florida Building Code (FBC) of 2001.
A total of 2,084 garage door permits were issued for the study homes in the eight months after Hurricane Charley hit the county in August 2004. The permits do not state the reason why the door was replaced. Thus, it cannot be guaranteed that permits issued after Hurricane Charley were directly related to the storm. However, storm damage is clearly the most likely cause of replacement.
$2.6 Million+ of Garage Doors
The average cost for garage door replacement was $1,241, and the replacement cost of all garage doors totaled $2,628,051. These numbers do not include Punta Gorda garage door replacements because the city does not issue that specific permit.
The total cost is probably conservative. Reasons: Permits are based on estimated costs, more garage doors have been replaced since the data was collected, and some installations likely occurred without a permit.
Overall, the study covered a geographic area with 43,228 single-family homes with garage doors. With the assistance of study partner, Applied Research Associates (ARA), wind speeds at the specific location of each garage door permit were estimated. The highest swath was calculated at 140-150 mph. Other areas were assigned lesser wind speeds at increments of 10 mph (e.g., 130-140 mph, 120-130 mph, etc.).
Graph #1: Doors Performed Better After 1994
Graph #1 charts the performance of all Charlotte County garage door permits issued from 1980 to 2004. The line is color coded to reflect the building code in use at the time of installation. This chart includes all replaced garage doors, without regard to the estimated site-specific wind speed.
For example, the 1993 number is 6.0 percent. That number means that six percent of all the garage doors installed (permitted) in 1993 were replaced after Hurricane Charley. In contrast, only 0.1 percent of the doors installed in 2003 were replaced after Charley. Thus, the 2003 garage doors performed much better than the doors installed 10 years earlier.
The highest replacement ratio of 7.1 percent occurred in homes built in 1988. The lowest replacement ratio (0.0 percent) occurred in 2004. The most dramatic improvement in performance occurred between 1993 (6.0 percent) and 1997 (0.9 percent).
Map #1: Plotting Replaced Doors
Each dot on Map #1 indicates a garage door on a single-family home in Charlotte County. White dots with blue trim represent garage doors that were not replaced after Hurricane Charley’s landfall. If the dot is filled with a color, that color indicates the building code in effect when that door was originally installed. For example, all red dots indicate a garage door that was replaced after Hurricane Charley, but was installed when the 1976 Standard Building Code was in effect.
The numbers from 3 to 11 indicate varying intensity of wind speeds. The most intense winds (140-150 mph) occurred in the 11 area. Each number less than 11 represents an increment of 10 mph less. Thus, the 9 area received winds from 120-130 mph.
Most replacements are located near the center of the hurricane track (areas 10 and 11), on homes built before 1994 and prior to the use of the 1991 SBC. The adoption of newer building codes appears to be related to the decreased replacement ratios.
BUILDING CODE YEARS ENFORCED
1976 Standard Building Code - 1980-1989
1988 Standard Building Code - 1989-1994
1991 Standard Building Code - 1994-1996
1994 Standard Building Code - 1996-1998
1997 Standard Building Code - 1998-2002
2001 Florida Building Code - 2002-2005
Key Conclusions About the Building Codes
Assuming that all study homes had their original garage door at the time of Hurricane Charley’s landfall, the following can be correlated between garage doors and building codes at all wind speeds.
• Garage doors installed under the 1976 SBC saw the highest replacement ratios. From 1980 to 1988, the average replacement ratio for these doors was 5.8 percent.
• Under the 1988 SBC, garage door replacement ratios saw very little improvement to doors installed under the 1976 SBC. From 1989 to 1993, the average replacement ratio was 5.7 percent. The 1988 SBC was a major step forward, but builders and installers were probably slow to comply with the new code.
• Under the SBC 1991 in 1994 and 1995, replacement ratios plummeted from 5.6 percent to only 1.3 percent. Hurricane Andrew’s 1992 landfall in the Miami-Dade area probably influenced an increased compliance with the code statewide.
• The data reveal more improvement in 1996 and 1997 under the 1994 SBC. The average replacement ratio for these two years dropped to 1.1 percent.
• The 1997 SBC was adopted from 1998 to 2001. Under this code, ratios for replacement were further reduced. The average ratio dropped to 0.5 percent.
• Under the statewide 2001 FBC, adopted in 2002, replacement ratios fell even further. None of the garage doors installed in 2004 were replaced. The average replacement ratio for 2002 to 2004 was a mere 0.05 percent.
Key Conclusions About Wind Speeds
When the data are analyzed by wind speed (e.g., 140-150 mph, 130-140 mph, 120-130 mph, etc.), similar trends are evident.
• Replacement ratios were highest from 1980 to 1993.
• A dramatic reduction in replaced garage doors occurred for doors installed from 1993 to 1997.
• From 2002 to 2004, replacement ratios dropped to near zero.
Key Conclusions About Garage Doors
In conclusion, it appears that the enhancements in the garage door industry and the building codes have substantially reduced damage to single-family homes in high winds. This reduced damage first appeared around 1994 when the county adopted the 1991 SBC. Garage door performance continued to improve up to and including the adoption of the Florida Building Code in 2002.