Treat multi-site lightning protection as a centrally governed risk-management program: use lightning risk assessment (ARF) outputs to set consistent protection classes and run a single maintenance regime across the portfolio. Start with a pilot site assessment, then roll out one technical specification and one inspection calendar everywhere else. That sequence keeps every building compliant without reinventing the design each time.

TL;DR:

  • Running a single lightning risk assessment across multiple sites enables consistent protection classes and simplifies maintenance scheduling for the entire portfolio.
  • An ARF should be performed on each site, with results consolidated into one protection level, referencing IEC 62305-2 standards and local zone risk zones.
  • Standardized protection components include external lightning protection systems, surge devices at service entrances, and internal bonding, all governed by IEC 62305-3 and IEC 60364-4-44.
  • Mutualizing earth terminations is feasible only if separation distances and risk zones are similar, and independent resistance measurements are maintained for each building.
  • Centralized inspection and maintenance, tracked via a CMMS, prevent slip-ups and ensure inspection consistency after system installation.
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Table of Contents

What counts as a multi-site program and when you need one

A multi-site program covers any group of buildings an owner manages under one risk policy: a corporate real estate portfolio, an industrial campus with several structures, or a regional cluster of warehouses and branches. The boundary is important because it determines how far you standardize design and maintenance versus adapting to each building’s footprint and exposure.

Several triggers usually justify moving from site-by-site decisions to a coordinated program:

  • You manage five or more sites with similar occupancy, equipment value, or regulatory exposure.
  • An insurer, auditor, or regulator asks for a single compliance record covering multiple buildings.
  • Recent construction, roof work, or new rooftop equipment has changed collection areas on several sites at once.
  • You want one contractor relationship and one maintenance calendar instead of a patchwork of local vendors.

Business and safety objectives drive the decision as much as regulation does. A consistent protection class across sites reduces audit complexity, and a shared maintenance schedule catches failures before they become outages or claims.

Running coordinated risk assessments across every site

A lightning risk assessment, or ARF, follows the procedure set out in IEC 62305-2, which defines how to combine loss components and choose a tolerable risk threshold for a structure. The 2024 edition introduced a single combined risk calculation and the lightning ground strike-point density (NSG) as inputs, replacing some of the older multi-risk breakdowns.

For a portfolio, running these assessments site by site only pays off when the results get consolidated into one policy. A practical sequence looks like this:

  1. Run an ARF on each site, following the loss-component and risk-threshold logic in IEC 62305-2.
  2. Identify zones and maximum measured risk (MMR) areas within each building, since a warehouse floor and a server room rarely carry the same exposure.
  3. Translate each site’s result into a required protection level (SPF class), then compare results across the portfolio.
  4. Set a portfolio minimum, usually the highest class required by any site with similar construction, so contractors install one standard rather than several.
  5. Document everything in a site risk matrix plus a technical study brief for each location.

Government ARF templates, including the SOCOTEC-style annex, illustrate what a complete deliverable contains: the R1 loss-of-life evaluation, a list of MMR zones, the resulting protection level, and a recommendation for a technical study (ET) where compartmentalization or special equipment is involved. That structure works as a template across every site in a program, which is what makes portfolio-wide comparison possible.

Choosing protections and matching them to standards

External lightning protection systems (LPS) share the same three components everywhere: air-termination, down-conductors, and earth-termination. IEC 62305-3 sets the design requirements for all three, along with protection against touch and step voltages near earth terminations. Internal protection is a separate layer: equipotential bonding, adequate separation distance between LPS components and internal systems, and dedicated protection for sensitive electronics.

Layered external and internal lightning protection

Surge protective devices (SPDs) belong at service entrances. IEC 62305-3 and IEC 60364-4-44 both call for SPDs where life-critical, public-service, or high-value assets sit behind the incoming power line, and IEC 62305-4 covers the internal system side of that same requirement.

A few practical notes matter across a portfolio:

  • Early-streamer emission air terminals (PDA) are referenced in NF C 17-102; confirm local acceptance of this standard before specifying PDA on a given site.
  • Earth resistance targets below 10 ohms appear in common technical design practice for lightning earthing, though the exact figure depends on soil conditions and the specific technical study.
  • Separation distance calculations change with building height and conductor routing, so a spec that works on one roof may not transfer directly to another.

IEC 62305-2:2024 introduced the lightning ground strike-point density (NSG) as a key input to risk calculation, replacing older regional strike-density assumptions with a more standardized procedure.

Coordinating design and installation across many buildings

A portfolio program needs one master technical brief derived from the ARF results, not a fresh design conversation on every roof. That brief sets the protection class, the SPD placement rules, and the acceptance criteria that every contractor on every site follows.

  1. Draft the master specification from the consolidated ARF outputs, then pilot it on one representative site before wider rollout.
  2. Decide where mutualizing conductors and earthing across adjacent structures makes sense, and where it does not: shared earth terminations can cut cost, but technical design examples show this only works when separation-distance calculations hold and the buildings share similar MMR zones.
  3. Run QA checkpoints at each phase, with acceptance tests covering earth resistance readings and joint integrity at every connection.
  4. Sequence permits, roof access, and mast anchoring early, and flag any planned mechanical or rooftop equipment work so the LPS design does not conflict with it later.

When mutualizing earth terminations between adjacent buildings, keep independent measurement points and access chambers for each descent conductor. That keeps resistance readings traceable per site, which matters later for audits and insurance reviews.

Pro Tip:Schedule the pilot site install during a dry season window if possible: earth resistance testing is more reliable when soil moisture is stable, and it gives you a clean baseline before replicating the spec elsewhere.

Coordinating contractor schedules across many sites is itself a project management problem; scheduling tools built for complex phased work, such as DesignFlow Build’s construction scheduling software, can help sequence pilot and rollout phases without double-booking crews.

Keeping inspections and maintenance consistent after installation

Once the systems are in, the work shifts to keeping every site on the same inspection cycle. A centralized maintenance calendar, tracked through a CMMS, avoids the common failure mode where one site’s inspection slips and nobody notices until a claim or an audit.

  • Log every inspection and corrective action in one system so the portfolio status is visible at any time.
  • Install strike-counting or monitoring devices on descent conductors to prioritize which sites need a visit first after a storm.
  • Check earth resistance, joint integrity, mast fixation, and SPD condition at every scheduled inspection.
  • Trigger an immediate re-evaluation after roof work, new rooftop equipment, or a recorded strike, since any of these can change collection areas enough to require design changes.

A CMMS platform such as Bold Factory’s CMMS can hold the inspection records, counting logs, and corrective-work history in one place, which is what makes a centralized maintenance regime practical rather than aspirational across a large portfolio.

Assigning responsibility and building the compliance record

A coordinated program only works when ownership is written down: who signs off on the ARF, who approves design changes, and which contractor is accountable for each site’s installation dossier.

The documentation set that supports both compliance and insurance review includes:

  • The ARF report and technical study (ET) for each site.
  • The installation dossier, including as-built drawings and acceptance test results.
  • Inspection reports and strike-counting logs, filed on the same schedule across every site.

Consistent protection levels backed by documented audits give insurers and regulators a single packet to review rather than a patchwork of local records, which tends to reduce both audit friction and liability exposure when a claim follows a storm event.

Why a portfolio approach beats site-by-site fixes

Most facility teams default to fixing lightning protection one building at a time, usually after an incident. That reacts to the last storm instead of the next one, and it leaves inconsistent protection classes scattered across a portfolio that an insurer or auditor will eventually notice.

The stronger approach treats lightning protection as an asset-availability program, not a capital project that ends at handover. Standards evolve, climate-driven strike patterns shift, and a single roof modification can quietly invalidate a design that was correct five years ago. A program built around consolidated risk assessments and R&D-informed design choices keeps pace with those changes instead of discovering them during an insurance audit.

— INDELEC

Getting started with a pilot site assessment

We specialize in lightning protection, including air-termination systems, grounding, surge protection, and engineering studies across industrial and commercial portfolios worldwide.

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For a portfolio, the fastest way to validate a program is to commission a pilot risk assessment and technical study on one representative site before committing to a full rollout.

FAQ

What is an ARF and why does it matter for multiple sites?

An ARF, or lightning risk assessment, is the procedure defined in IEC 62305-2 for combining loss components and setting a tolerable risk level for a structure. Across multiple sites, consolidated ARF results let you set one portfolio-wide protection class instead of negotiating a different standard for each building.

Which standards govern multi-site lightning protection design?

The IEC 62305 series covers the full scope: Part 2 for risk management, Part 3 for physical damage and LPS design, and Part 4 for internal systems and surge protection, alongside IEC 60364-4-44 for SPD requirements at service entrances. In France, NF C 17-102 additionally governs early-streamer emission air terminals.

Can conductors and earthing be shared between adjacent buildings?

Mutualizing conductors and earth terminations can reduce installation cost, but it depends on separation-distance calculations holding across both structures and on similar risk zones, as shown in technical design examples. Keep independent measurement points for each descent conductor so resistance readings stay traceable per building.

What triggers a re-evaluation of an existing multi-site program?

Roof work, new rooftop equipment, antenna installations, or a recorded lightning strike can all change a building’s collection area or separation distances enough to require a new assessment. A single structural change on one site can mean an ARF addendum and a design update even if the rest of the portfolio is unaffected.

Do we offer ARF and maintenance services for multiple sites?

We provide risk assessment, technical studies, installation, and maintenance for lightning protection programs covering single buildings and larger portfolios through our protection services page. Pricing depends on site count and scope, and is available on request.

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