New Lightning Protection Standard (ČSN EN IEC 62305 ed. 3): What Is Changing and What It Means for an Existing System

The call from the contractor is usually brief: “There is a new lightning protection standard, so your facility will need to be redone.” Two days later, a quotation lands in your inbox, including a charge for recalculations that nobody had mentioned before. The set of lightning protection standards has indeed been redesignated and issued in a third edition—but between “there is a new standard” and “you must rebuild your completed lightning protection system” lies a chain of assumptions, most of which do not hold true under Czech law.

This article answers one question: what will edition 3 mean for a lightning protection system that is already installed on a building? Whether you need lightning protection at all, how risk analysis works and what the protection classes mean are covered separately in our article on lightning protection according to ČSN EN 62305.

What Has Been Published and When It Takes Effect

The designation has changed from ČSN EN 62305 to ČSN EN IEC 62305 ed. 3. “IEC” has been added to the title as a formal consequence of the way the European standard is adopted. This is a continuation of the same series, not a standard from an entirely different system. The individual parts were published at different times, which is why quotations and inspection reports may contain different dates.

For Parts 2 and 4, check the exact date in the Věstník ÚNMZ or the ČAS agency catalogue. The publication date and effective date are not the same, and even industry professionals sometimes confuse them when a series is published in stages.

The date that matters most, however, is a different one: the published parts state that the second edition remains concurrently valid until 31 October 2027. Until then, both editions will exist side by side. After that date, the previous edition will be withdrawn and edition 3 will remain the current valid standard—the usual means of demonstrating that a solution has been designed correctly. Using the withdrawn edition will not automatically become prohibited, because a Czech technical standard is not generally binding, but the designer will have to provide a professional justification and demonstrate that the solution complies with legal requirements. When commissioning a design, ask for the exact designation: “according to ČSN EN 62305” is no longer an unambiguous brief.

A Standard Is Not a Law, and the Regulation Governs Design

For an existing, functional lightning protection system, the new edition does not in itself require the air-termination system to be rebuilt, additional down conductors to be installed or the earth-termination system to be altered. This does not mean that the system’s condition should not be assessed; it simply means that publication of the standard is not the trigger. This rests on two principles worth knowing, as they can help you challenge a contractor’s claims.

A Czech technical standard is not generally binding. This is stated expressly in § 4 odst. 1 zákona č. 22/1997 Sb., and the publication of a new edition does not change it. Two separate factors then determine the role of the standard. The first is how legislation refers to it: a reference may be exclusive, requiring compliance with a specific standard, as § 16 vyhlášky č. 146/2024 Sb. does with the wording “musí být navrženy a provedeny v souladu s normou uvedenou v příloze č. 14”; alternatively, it may be indicative, in which case compliance with a harmonised or designated standard is deemed under § 4a odst. 3 zákona č. 22/1997 Sb. to satisfy the requirements to the extent and under the conditions laid down by the technical regulation, without prohibiting another demonstrably compliant solution. The second factor is your own contractual position: the design brief, the contract with the supplier or the terms of your insurance may require compliance with a particular edition. In practice, this is the most common reason why a standard “must” be followed—but it is a contractual obligation towards another party and does not change the standard’s generally non-binding nature.

Building regulations focus on the time of design and construction. Lightning protection in construction is governed by vyhláška č. 146/2024 Sb. o požadavcích na výstavbu (effective from 1 July 2024, replacing vyhláška č. 268/2009 Sb.). Its § 26 requires lightning protection to be “designed and installed” for storage facilities and plants handling explosive and flammable substances, for above-ground parts of designated gas equipment, and wherever a strike could endanger the life or health of people or animals or cause substantial damage. The requirement is expressed in functional terms: příloha č. 14 vyhlášky, which lists the ČSN standards associated with its individual provisions, does not specify any standard for § 26, and the designation 62305 does not appear in the regulation. The wording concerns design and installation; it does not impose a duty to retrofit a building that was lawfully constructed in accordance with the knowledge and requirements applicable at the time.

Operation is a third, separate area. A lightning protection system is classified as vyhrazené technické elektrické zařízení: nařízení vlády č. 190/2022 Sb. includes equipment protecting against atmospheric and static electricity among designated equipment in § 3 odst. 1 and links periodic inspection intervals to its příloha č. 4 in § 7 odst. 5 písm. d). This regime applies to operators under zákon č. 250/2021 Sb., meaning legal entities and self-employed natural persons. For a privately used family home, the obligations arise primarily from building law and the insurance contract. The intervals depend on the LPS protection class, not on the edition of the standard—the new edition does not alter them. They are discussed in detail in our article on lightning protection system inspection intervals.

In practical terms, the end of concurrent validity does not in itself require any alterations to a facility completed in 2016 with a lightning protection system designed under the second edition. Withdrawal of a standard does not invalidate an installation built in accordance with it. However, this does not automatically mean that everything is satisfactory. That can only be determined through an individual assessment of the system’s actual condition, the changes made to the property and its use since installation, and the legal requirements that apply today. An inspection assesses the actual condition: corrosion at the point where a conductor enters the ground, broken connections, a test joint buried beneath thermal insulation, or new metal structures on the roof. Compliance with the original design alone does not guarantee safety.

When Edition 3 Will Actually Affect You

The transition period is not about whether a building must be altered. It is about which rules will be used for a new design. Edition 3 will become relevant to your building in the following situations:

• New construction, an extension or the addition of another storey. Until 31 October 2027, the designer may use either edition. After that date, edition 3 will be the current edition, while using the withdrawn edition will require a specific professional justification.
• Refurbishment affecting the roof or building envelope. This includes new roofing, thermal insulation, replacement of sheet-metal components or replacement of a facility’s cladding. Down conductors must be reattached and the air-termination system reinstalled. The designer will determine which edition should be used to recalculate that part, based on the design date, the scope of the work, transitional provisions, continuity with the existing documentation and the contractual brief. Parts from different editions of the series should not be mixed indiscriminately.
• Installation of photovoltaics. This is the most common trigger. Panels and their support structures occupy space originally designed to remain empty, introduce additional conductive parts and add DC cable routes. The protected volume of the air-termination system and the separation distance must be recalculated, while surge protection must be addressed on both the DC and AC sides. This must be resolved in the design before installation, not in the inspection report afterwards. We discuss the wider implications in our article on fire safety for rooftop PV systems.
• A change in the building’s use or internal technology. A warehouse becomes a production facility, or a server room, cooling system or fire detection and alarm system is added. This changes the inputs to the risk analysis under Part 2—and therefore its outcome.
• After a lightning strike or severe storm. An extraordinary inspection is not about which edition applies, but the technician will generally also consider whether the original design still reflects the building’s current use.

The difference between “no action needed” and “recalculation required” is therefore determined not by a date in the calendar, but by alterations to the property:

We perform lightning protection inspections and assessments following roof alterations for businesses, condominium owners’ associations and municipalities. If you do not have your own technician and do not want to guess whether recalculation is necessary, we will assess it for you and explain what it means for your next inspection.

What Has Actually Changed in Edition 3

The changes are not merely cosmetic, but neither are they revolutionary. The main points identified in the available summaries are as follows:

Part 1 aligns definitions with developments in IEC and adds information on lightning current parameters for laboratory testing of components. It distinguishes services in the public interest—such as hospitals, energy supply and water utilities—from other structures. For public-interest services, the required protection level is determined by the competent authority; for other structures, the decision remains with the owner. It introduces the use of damage frequency and comparison with a tolerable value, focusing on the operational continuity of internal systems. The sizing of surge protection devices for individual sources of damage has also been clarified.

Part 3 refines the practical design rules: it clarifies the calculation of separation distance, adds minimum thicknesses for metal sheets and pipes where puncture or hot-spot problems must be prevented, refers to the series covering LPS components and adds annexes on topics that were previously insufficiently addressed—green roofs and the protection of high-rise façades. A green roof on an office building is no longer unusual, and the question of how to route the air-termination system through the substrate had previously been left open to improvised solutions.

Part 4 imposes stricter requirements on surge protection coordination and the shielding of cable routes within the structure. For a business with production control systems, a server room or photovoltaic inverters, this is the part of the series with the greatest practical impact—and also the one where savings made during installation may only become apparent after the first storm.

The reference to the standards covering lightning protection system components (ČSN EN IEC 62561) is more relevant to building owners than it may appear. It shifts the emphasis from “something was welded in place” to components with documented testing, including clamps, connectors and earth electrodes. For an LPS being repaired later, this translates into one very specific issue: what should appear on the delivery note when a contractor replaces ten clamps.

Five Things to Request at Your Next Inspection

1. The basis on which the LPS was installed. The report should state the edition and the year of the design, not merely “ČSN EN 62305.” Without this information, it is unclear which benchmark the technician used.
2. A distinction between a defect and a deviation from the new edition. A broken down conductor is a defect. A solution that complies with the original design but would be designed differently today is not necessarily a defect in itself. However, if the technician finds that the actual installation or the building’s current use does not provide the required safety, it is a defect regardless of what appears in the original design. By contrast, a deviation from the new edition with no impact on safety should be recorded as a reasoned recommendation. If the report merely lists instances of non-compliance with edition 3, request references to the specific provisions and an explanation.
3. Measured values in a table, compared with the previous report. Without figures, an increasing earth-electrode resistance cannot be identified—and for an earth-termination system, the trend is more informative than a single reading.
4. A record of changes to the property since the previous inspection. Photovoltaics, air-conditioning units, antennas, new roofing and thermal insulation should all be included.
5. An assessment of the separation distance if anything has been added to the roof.

If the lightning protection design is missing—a common situation for buildings from the 1980s and 1990s—you face a more serious problem than the edition of the standard. The technician has no reference against which to compare the actual installation, and the report will include a reservation concerning the limited scope of the assessment. We explain how the necessary documents can be traced and supplemented in our article on lightning protection documentation for an older building.

What to Do by 31 October 2027

Three steps, with no additional investment required.

1. Find out which rules were used to build your LPS. Is there a design? A previous inspection report? A risk analysis specifying the protection class? These are the only records with real weight in a dispute. Property insurance policies commonly require equipment to be maintained in accordance with applicable regulations and inspection records to be produced, but the specific obligations arise from the contract, not from the standard.

2. For planned construction work and photovoltaic installations, agree on the edition in the brief beforehand, even though both editions are permitted during the transition period. The choice belongs to the designer, who will assess it according to the design date, the scope of the change, transitional provisions and continuity with the existing documentation. However, the contractual brief is one of the relevant inputs, so the contract should be unambiguous and parts of the series should not be mixed randomly across editions. A design prepared today under the old edition may create additional work when the property is altered again.

3. For photovoltaics, follow the sequence assessment → installation → inspection. The effect of the PV system on the air-termination system, separation distance, bonding and surge protection must be resolved by a qualified professional before installation, with the LPS and PV designs coordinated. A subsequent inspection cannot replace either the design or this coordination. Only after installation should the appropriate initial inspection of the electrical installation and, where applicable, an extraordinary LPS inspection take place. Do not schedule a periodic lightning protection inspection immediately before work on the roof: the system will have to be assessed again afterwards anyway.

The new edition does not in itself change the scope of a periodic inspection. Recalculating the LPS because of photovoltaics or refurbishment is, however, a separate design task rather than an item in the inspection report, so it should be included separately in the construction budget from the outset.

Sources for This Article

• Lightning protection system inspections – a service provided by SOHE.
• Lightning protection according to ČSN EN 62305: when it is required and what it must provide – when the obligation arises, how risk analysis works and what the protection classes mean.
• Lightning protection inspections: how often under ČSN EN 62305 – periodic inspection and visual inspection intervals by protection class and type of property.
• Lightning protection documentation for an older building – what to do when the design is missing and the technician has no documentation against which to compare the installation.
• Zákon č. 22/1997 Sb. – o technických požadavcích na výrobky; § 4 odst. 1 states that a Czech technical standard is not generally binding, while § 4a odst. 3 governs the effect of references to harmonised or designated standards.
• Zákon č. 250/2021 Sb. – o bezpečnosti práce v souvislosti s provozem vyhrazených technických zařízení; defines the operator’s obligations.
• Nařízení vlády č. 190/2022 Sb. – o vyhrazených technických elektrických zařízeních; § 3 odst. 1 includes protection against atmospheric electricity, while § 7 odst. 5 písm. d), together with příloha č. 4, establishes periodic inspection intervals.
• Vyhláška č. 146/2024 Sb. – o požadavcích na výstavbu; § 26 concerns the design and installation of lightning protection, while příloha č. 14, listing the ČSN standards associated with individual provisions of the regulation, does not specify a standard for this section.
• ČSN EN IEC 62305 ed. 3, Parts 1 to 4 (and the previous ČSN EN 62305 ed. 2), together with the ČSN EN IEC 62561 series for lightning protection system components. The standards are not freely available and are sold by the ČAS agency.

This article is for information only and does not constitute legal advice. The specific lightning protection arrangements and inspection intervals must be determined according to actual operations, the manufacturer’s documentation, the conditions of use and the risk assessment.

Not sure which rules were used to build your lightning protection system or whether the transition to edition 3 affects you at all? We will review the documents and inspect the roof, then explain exactly what this means for your next inspection. We provide lightning protection system inspections for businesses, condominium owners’ associations and municipalities. Send us a non-binding enquiry or email info@sohe.cz. If you are planning photovoltaics or roof refurbishment, contact us sooner rather than later: a recalculation commissioned in advance costs less than alterations to a finished façade.