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Hurricane Damage Assessment on Assessing the Integrity of Metal Wall Panels in High-Wind Zones
Metal wall panels are a popular choice for building exteriors due to their durability, aesthetic appeal, and low maintenance. These panels are widely used in commercial, industrial, and even residential settings. However, in areas prone to hurricanes or high winds, the long-term performance of metal wall panels becomes a critical concern. This blog will discuss metal panel types, the importance of routine assessments, and steps involved in evaluating the integrity of metal wall panels, particularly in hurricane-prone regions.
Types of Metal Wall Panels
Metal wall panels can be broadly categorized based on their fastening systems:
Exposed Fastener Panels: These panels are attached to the structure with visible screws or nails. This type of system is relatively easy to install and inspect but may be more vulnerable to wind loads and moisture intrusion if not properly maintained.
Concealed Fastener Panels: These panels offer a cleaner aesthetic because the fasteners are hidden beneath the panel’s surface. While more visually appealing, concealed fastener panels can be more prone to failure under high wind conditions if not adequately secured.
Why Routine Assessment is Essential
Hurricanes and high-wind events expose wall systems to extreme forces, including wind-borne debris. Even if metal wall panels remain intact after a storm, repeated exposure can weaken their structural integrity over time. Proper assessments ensure that the wall system is capable of withstanding future events, especially in regions where wind speeds can exceed 135 mph.
Both the International Building Code (IBC) and ASCE 7 standards do not require specific tests for wind-borne debris resistance for wall systems. However, FEMA recommends testing critical facilities using missile impact tests defined in ASTM E1996 for better resilience.
Level 1 Assessment of Metal Wall Panels
A Level 1 assessment is the first step in evaluating metal panels for wind resistance and long-term durability. This assessment involves a non-invasive, preliminary check to gather information about the panel system.
Steps in a Level 1 Assessment:
Visual Inspection:
Check the panel surfaces for dents, loose fasteners, corrosion, and other visible signs of damage.
Examine seams and joints for any misalignment or gaps.
Verify that the metal panels are properly installed, and that there are no bulges or warped areas.
Spot-Checking Fasteners:
Remove a few fasteners to confirm their type, size, and condition. This ensures they are still providing sufficient resistance to wind loads based on the current ASCE 7 design requirements.
For panels with snap-on battens (common in concealed systems), perform a manual check by trying to rotate or move the batten. Weak or loose battens can be a sign of inadequate wind resistance.
Assessing Wind-Borne Debris Resistance:
While not required by building codes, check whether the metal panel system could resist debris impact. Panels in areas with wind speeds over 135 mph may benefit from being tested against ASTM E1996 to assess their ability to withstand debris impacts.
Evaluate Framing:
Examine the underlying framing for signs of wear or damage, particularly around corner areas, which are subjected to the greatest wind pressures.
Ensure that the fasteners connecting the panels to the structure are in good condition and meet wind-load requirements.
If the Level 1 assessment suggests the panel system is aging but has several years of service life remaining, a more detailed Level 2 assessment may be recommended, especially if the building is located in a high-wind zone.
Level 2 Assessment of Metal Panels
A Level 2 assessment is more invasive and typically involves removing some of the metal panels to inspect the underlying components such as weather-resistive barriers (WRB) and framing systems. This level of inspection is recommended for:
Buildings located in regions with wind speeds above 120 mph for concealed fastener panels or 165 mph for exposed fastener panels.
Structures where the panels extend more than 30 feet above grade.
Steps in a Level 2 Assessment:
Panel Removal:
Remove at least one panel from a corner area and one from the field of the wall to examine the presence and condition of a WRB (e.g., asphalt-saturated felt or house wrap). If the WRB is damaged or missing, this could lead to significant moisture issues or even panel detachment during high winds.
Fastener Evaluation:
For concealed fastener systems, remove a few clip fasteners to assess their size and type. Compare these fasteners to the design loads outlined in ASCE 7. Fasteners that don’t meet the required standards increase the risk of panel failure during a hurricane.
Check if metal panels are made from copper and whether their fasteners are compatible (e.g., copper or stainless steel clips), to prevent galvanic corrosion.
Inspect Framing Integrity:
If the framing is wood, verify that the framing connections are secure and that they are properly attached to the building structure.
If the system uses metal hat channels, ensure that these are correctly fastened, with attention given to their attachment at both top and bottom flanges along the vertical line.
Conclusion
Metal wall panels are a durable and reliable cladding system, but buildings located in hurricane-prone regions require regular assessments to ensure that these systems remain secure and functional. Both exposed and concealed fastener panels should be evaluated for wind resistance, fastening integrity, and their ability to withstand wind-borne debris.
By conducting Level 1 and Level 2 assessments as needed, building owners and facility managers can identify and address vulnerabilities before a storm strikes, ensuring both safety and longevity for their metal wall panel systems.