Wind Uplift Testing

In 2024, ILD undertook laboratory wind uplift testing of its VECTOR MAPPING GRID™ (VMG™).

International Leak Detection (ILD) is a provider of rooftop leak detection and monitoring systems that protect buildings and assets around the world. To ensure our technology continues to be top tier, delivering uncompromised services to clients, we periodically undertake testing of our leak detection and monitoring solutions. In this article, we’re pleased to share the results of recent Wind Uplift Testing.

A building obstructs wind flow, altering the direction of airflow and pressure on the building surface. This can happen windward (the side of a building that’s facing the wind) or leeward (the side of the building that’s sheltered from the wind, downwind). Wind can cause significant damage to a roof including roof detachment and weakening which may occur indirectly from the impact of wind-borne debris or directly through the pressure it exerts.

Testing wind uplift, the upward-acting pressure on a roof’s components resulting from wind traveling across the roof, is important to determine the positional stability against wind loads on roof systems. Wind uplift is a force expressed in pounds per square foot (psf). It occurs when the pressure beneath a roof exceeds the pressure above it. This effect becomes more pronounced during high winds, as air infiltrates the building and raises the pressure below the roof, while the wind’s speed over the roof decreases the pressure above. If wind uplift exceeds the building system’s design capacity, it could in a worst-case scenario, cause the roof deck to detach from the supporting structure.

ILD undertook laboratory testing of its Vector Mapping Grid (VMG) when installed as a component within various roofing membrane assemblies. To do this, ILD contracted with WJE (Wiss, Janney, Elstner Associates, Inc.), a global firm of engineers, architects, and materials scientists committed to helping clients solve, repair, and avoid problems in the built world.

ABOUT VECTOR MAPPING GRID™ (VMG)

The Vector Mapping Grid (VMG) is a patented conductive medium system designed to test non-conductive substrates that incorporate Electric Field Vector Mapping leak detection systems. For roofing applications, the grid can be positioned either directly beneath cover board or directly under membrane and above cover board within a roofing assembly. These two grid placement positions were used in the mock up samples to determine which position within the roof assembly is preferrable from a structural perspective.

Advantages of Vector Mapping Conductive Mediums include:

• Early detection of breaches in fully adhered single ply built up roofs after installation
• Allows for testing of non-conductive structural decks
• Minimizes the ground fault connection from the lightning protection system

TESTING METHOLODOGY

Sample Fabrication

The goal of the testing was to determine the tensile strength of select roofing assemblies containing the VMG when subjected to uplift loads. Preliminary steps included development of the test program, pull tests to determine which adhesive product was more appropriate to use, creation of 12-inch x 12-inch mock-up samples fabricated using different membrane types, and testing to determine the location of the failure plane(s) and uplift loads at failure.

Trial Testing

Following fabrication of the mock-up samples, they were tested in direct tension to simulate uplift loading. WJE used their SATEC Universal Testing Machine. The SATEC is a static servo-hydraulic universal testing machine with the ability to exert up to 120,000 pounds of force for both tensile and compressive strength testing, to determine the maximum uplift load able to be withstood. The testing was performed in a static manner, with the load applied at a constant rate, until failure. A 0.05 inch per minute load was used because it is a common load rate for testing adhesives used in building construction.

Review of Testing

The testing showed that the test methods developed were appropriate for determining maximum tension loads on roof samples containing VMG. All samples demonstrated significant uplift capacity and ability to resist anticipated wind loads. In most of the tests, the failure occurred within the insulation – between the facer and the rigid foam or within the rigid foam. In 5 of the 17 tests, the failure occurred between the top plywood backer plate and the membrane, however, significant tension loads were still resisted by the samples.

CONCLUSION

The preliminary testing trials revealed that the test methods developed can produce failure planes within the roofing assemblies and not only at the plywood backer plate bond lines. WJE was able to achieve results indicative of uplift loads that would cause failure within roofing systems. Placement of the VMG either below the membrane or below the cover board does not appear to have a significant impact on the ability of the roof systems to resist code prescribed wind uplift loads. One sample of each configuration was tested. This testing trial may be considered a preliminary indicator of more extensive sample testing.

If you’d like to see the full Wind Uplift Testing report, please contact ILD.