Maintaining Integrity: Lightning Protection Systems During Commercial Reroofing Projects

For engineers, architects, and building specifiers, the integrity of a structure's lightning protection system (LPS) is paramount, especially when undertaking significant maintenance such as commercial reroofing. While most LPS components are designed for longevity, roofing systems require periodic servicing or replacement. This presents a critical juncture where the existing lightning protection infrastructure must be meticulously managed to ensure continuous building envelope protection against the devastating impact of lightning strikes.

The Indispensable Role of Lightning Protection Systems

A comprehensive LPS functions by creating multiple, low-impedance paths for lightning current to safely traverse a structure and dissipate into the earth. Beyond the below-grade components, the rooftop elements are the initial line of defense. These typically include:

• Strike Termination Devices: Primarily air terminals (lightning rods), these components are strategically positioned above the roof surface and rooftop equipment to intercept direct lightning strikes, preventing structural damage.
• Conductors: Large-diameter, multi-strand cables interconnect strike termination devices and provide the crucial connection to down conductors, facilitating current flow from the roof to the grounding systems.
• Through-Structure Assemblies: These specialized fittings enable lightning conductors to penetrate the roofing, insulation, and roof deck, linking the rooftop network with the vertical down conductors and the comprehensive grounding system.

All components integrated into a modern LPS must be UL-listed and installed in strict adherence to ANSI-approved standards, including NFPA 780—Installation of Lightning Protection Systems, alongside relevant standards from the Lightning Protection Institute (LPI) and UL 96A. This ensures the system's efficacy and compliance with industry best practices.

Strategic Planning and Professional Execution

The National Roofing Contractors Association (NRCA) explicitly states that the installation, evaluation, and maintenance of LPS extend beyond the expertise of typical roofing contractors. It is an imperative that all lightning protection work be performed by LPI-certified professionals. These specialists possess the in-depth knowledge of lightning protection standards and construction methodologies required to prevent system defects and potential liabilities, as detailed in this technical documentation from ECLE.

Prior to reroofing, qualified lightning protection professionals must conduct a thorough site assessment. This involves meticulously documenting and marking the precise locations of existing rooftop LPS components, particularly thru-roof assemblies, to facilitate their reinstallation or replacement. A critical decision at this stage is whether to salvage and reuse existing components or install new ones. While salvaging might seem cost-effective, new UL-listed components often ensure better compatibility with new roofing materials and adherence to current standards, enhancing the overall building envelope protection.

Ensuring System Integrity and Equipotential Bonding

Coordination between the roofing contractor and the lightning protection professional is essential. This includes agreeing on adhesive compatibility, potential requirements for additional roofing membrane layers, and sequencing of work. During reroofing, temporary lightning protection measures may be necessary, especially for mission-critical facilities or structures housing combustible materials. Furthermore, the opportunity should be seized to inspect and repair all accessible LPS components, addressing any damage from corrosion, mishandling of HVAC equipment, or unauthorized additions to the roof.

A crucial aspect of restoring LPS integrity involves establishing robust equipotential bonding. All metallic fabrications and rooftop appurtenances—such as parapet copings, ladders, access hatches, railings, signs, and HVAC units—must be properly bonded to the LPS. This prevents dangerous side flashes and ensures that lightning current can safely transition to ground through the designated paths, maintaining electrical continuity across the entire building structure.

The ultimate goal is a certified LPS. The Lightning Protection Institute Inspection Program (LPI-IP) offers certifications, including the Reconditioned Master Certificate for existing structures, affirming that the entire system—both rooftop and below-roof—meets current standards. By prioritizing certified design, professional installation, and rigorous inspection, engineers and architects can ensure that reroofing projects enhance, rather than compromise, the long-term lightning safety of their valuable assets.

Source:
Reroofing and Lightning Protection
Building Enclosure, March 2022