Large missile impact testing is a hurricane-resistance test used to determine whether a building component can withstand impacts from large wind-borne debris. In Florida, this testing is especially important in areas exposed to hurricanes and high winds, including the High-Velocity Hurricane Zone (HVHZ). Depending on the roof assembly and the part of the building envelope being evaluated, large missile impact requirements can apply to roofing systems, roof panels, skylights, and other roof-related components.
The term “large missile” does not refer to a weapon. It refers to a standardized piece of wood used to simulate large debris carried by hurricane-force winds. Under Florida’s HVHZ testing provisions, the large missile is a nominal 2-by-4 timber weighing approximately 9 pounds and is propelled at about 50 feet per second. The testing is performed on representative specimens of the complete assembly, including relevant framing and anchorage.
Does Large Missile Testing Apply to Roofs?
Yes, in certain circumstances. Large missile impact resistance can apply to roof assemblies and roof components when required by the applicable Florida Building Code provisions, product approval, or project specifications.
Florida’s HVHZ provisions specifically address impact resistance for building-envelope components, including roofs and skylights. The code states that applicable portions of the building envelope must meet impact criteria or be protected by an external protection device that meets the required criteria.
Miami-Dade County’s product approval database also identifies roofing products and roof assemblies that have been evaluated for large and small missile impact. This demonstrates that impact testing is not limited to windows and shutters; certain roofing products are specifically tested and approved for impact resistance.
How Is the Test Performed?
A large missile impact test generally involves installing the product or assembly in a laboratory configuration that represents its intended field installation. The standardized missile is then fired at specified locations on the test specimen.
For Florida HVHZ testing, the code requires three test specimens for the large missile test. The assembly must be tested as supplied for installation, including the appropriate frame and anchorage. The impact locations and test conditions are prescribed by the applicable testing protocol.
Miami-Dade uses TAS 201 for large missile impact testing. Depending on the product, additional testing such as TAS 202 for static loading and TAS 203 for cyclic wind pressure may also be required. Miami-Dade product approvals show these protocols being used together for impact-resistant building products.
What Does This Mean for a Commercial Roof?
Large missile testing does not mean that every commercial roof in Florida must independently undergo a missile test after installation. Typically, the important question is whether the specific roof product or assembly has the required approval or testing for the location and application.
For example, a commercial property in South Florida may use an approved metal roof panel, skylight, or other roof component that has already undergone the required impact testing. The contractor must then install the approved system according to its tested and approved configuration, including required fasteners, spacing, substrates, and other details.
This distinction is important because changing the installation configuration can affect the validity of an approval.
Large Missile Testing vs. Wind-Uplift Testing
Large missile impact resistance and wind-uplift resistance are not the same thing.
Impact testing evaluates how a component responds when struck by simulated wind-borne debris. Wind-load testing evaluates whether the assembly can withstand the pressures generated by hurricane winds. A roof can therefore require both impact resistance and structural wind-pressure performance.
For commercial roofing projects in Florida, the applicable requirements should be determined from the building’s location, wind zone, occupancy, roof system, roof geometry, and the current Florida Building Code and approved product documentation.
What Should Building Owners Ask Their Roofing Contractor?
Before installing or replacing a commercial roof in a hurricane-prone Florida location, owners should ask:
-
Is this roof assembly approved for the project’s location?
-
Does the product have the required Florida or Miami-Dade approval?
-
Does the approval cover the exact roof application?
-
Are large missile or other impact requirements applicable?
-
Does the installation match the tested configuration?
-
What wind-uplift rating is required for the project?
-
Are roof-mounted skylights, equipment, or other components subject to separate requirements?
Bottom line: Large missile impact testing is a standardized hurricane-debris resistance test, and it can apply to commercial roofs and roof components in Florida, particularly where HVHZ or project-specific impact requirements apply. The key is not simply choosing an “impact-resistant” product; the roof system must have the appropriate approval and be installed according to the approved configuration.
For a Florida commercial roofing project, Shieldline Roofing can help evaluate the existing roof, identify applicable code and product-approval requirements, and determine whether repair, restoration, or replacement is the appropriate solution.
Related Questions
- What impact rating is required for skylights in the HVHZ?
- Are impact-rated skylights required in the HVHZ?
- How do Florida’s HVHZ requirements differ from the rest of the state?
- What wind uplift concerns apply to loose-laid pavers in Florida?
- How are skylights protected from impact damage?
- How are hurricane shelter roofs designed differently from other school buildings?
- Does Florida experience enough hail to affect roof specification?
- What is a flood test and when should one be performed?
Commercial Roof Leak Detection & Repair
