Lightning protection design: when it is required, what it includes and what drives the price

28 October 2026 · 6 min read

Lightning protection systems still get built without a design – and the inspection then ends with reservations. When protection is required, what the design must contain and how it is priced.

When lightning protection is required

The answer has two parts: the regulation and the calculation. The Czech building regulation (Decree No. 146/2024 Coll., Section 26) requires lightning protection wherever lightning could endanger life or health – it explicitly names residential buildings and public buildings – or cause considerable damage, and always for production and storage of flammable and explosive substances. Whether a particular house, hall or school falls into that group is not decided by guesswork but by a risk assessment under EN 62305-2. It compares the risk of loss of human life (and, where relevant, economic loss) with the tolerable value; if the risk without protection exceeds it, a lightning protection system is required and the calculation also sets the protection class LPS I to IV.

In practice this means the risk is calculated for every new building and every major change – new rooftop PV, an extension, a change of use. The result cannot be predicted in advance: two similar houses can come out differently depending on location, structure and the lines entering them. The building authority routinely asks for the calculation and the design in the permit documentation, and the inspector needs documentation to verify the installation after assembly.

Lightning protection without a design

An installer can build a lightning protection system by habit, “by eye”. The problem appears later: the inspector has nothing to verify that all parts of the roof lie within the protected volume of the air terminations and that the separation distance from metal parts and the electrical installation is kept. The inspection then either fails or ends with reservations that are expensive to fix on a finished roof. In an insurance claim, the question is whether the protection complied with the standard – and that cannot be proved without a calculation and drawings. A lightning protection design is therefore cheaper than fixing the system afterwards.

What the design contains

Part	What it contains
Risk assessment	Calculation under EN 62305-2 with a report: input data on the building and its surroundings, calculated risks, choice of LPS class and other measures (surge protection, fire measures).
Air-termination system	Roof plan with the air-termination conductors, rods and auxiliary terminations on chimneys, dormers and equipment; verification of the protected volume by the rolling sphere or protection angle method – in our case in 3D on the actual roof shape.
Down conductors	Number and position according to the LPS class, test joints and, on buildings with PV or metal equipment, insulated down conductors (HVI) where the separation distance cannot be kept.
Separation distance	Calculation of the minimum distance between the LPS and metal parts or the electrical installation so that lightning does not flash over between them; solutions for places where it cannot be kept.
Earthing	Type A earth electrodes (rods and strips at the down conductors) or type B (ring or foundation earth electrode), calculation of the required electrode length and estimate of earth resistance, bonding to the installation earthing.
Surge protection	Type 1 to 3 surge protective devices in the switchboards, their coordination and location – protecting inverters, heat pumps, control systems and electronics.
Elevations and details	Facade views with the down conductors, details of the connection at the eaves, the transition to the earth electrode and the fixing of air terminations on the roofing.
Technical report and bill of quantities	Description of the solution, standards applied, installation conditions, material list for tendering installers and a basis for the inspector.

For a family house this means two or three drawings and a technical report; for a hall, a school or a battery storage plant a more extensive documentation including coordination with the protection of the equipment and the transformer station.

Lightning protection for solar PV

Panels on the roof are the most common reason a lightning protection design is ordered today. They change the situation even where a system already exists: new highest points have appeared, a new path for lightning current leads into the building along the DC cables, and the existing system no longer matches the state it was designed for. Panels must not be part of the air-termination system and must not lie too close to it – which is why the separation distance is calculated and insulated down conductors are often designed. Details in the article on lightning protection for solar PV.

What drives the price of the design

Roof size and shape – a simple gable roof of a house is a different scope from a complex roof with dormers, terraces and chimneys, or a flat roof of a hall covering thousands of square metres.
Protection class from the calculation – a higher LPS class means a denser air-termination system, more down conductors and a more detailed treatment of the separation distance.
Equipment on the roof – PV, ventilation units, antennas and metal structures add separation distance calculations and often insulated down conductors.
Design stage – only the design for the permit, or also the detailed design with details and a bill of quantities and the as-built documentation for the inspection.
Input documents – DWG drawings of the building and elevations shorten the work; existing buildings without documentation are surveyed or captured by drone.
Context – lightning protection as part of an electrical, PV or storage design is cheaper than a separate order, because earthing and surge protection are solved once.

We set a fixed price for the design after reviewing the input documents. The whole service is described on the lightning protection page; the link to the house design is covered in the article on the electrical installation design for a family house.

What we need from you

floor plans and elevations of the building (ideally DWG or PDF); for existing buildings at least photographs of the roof from all sides,
the location of equipment on the roof – PV, air conditioning, chimneys, antennas,
information on the existing lightning protection and earthing, if any, and on the power supply,
the purpose of the building and its occupancy – both enter the risk assessment.

Frequently asked questions

Is a lightning protection system mandatory on a family house?

The regulation requires it wherever lightning could endanger people, and it names residential buildings explicitly; for a specific house the risk assessment under EN 62305-2 decides, and the building authority usually requires it in the permit documentation. The result cannot be predicted – it depends on the location, the structure and the lines entering the house.

Is a “template” lightning protection design in PDF from the internet enough?

No. The risk assessment, the protected volume of the air terminations and the separation distance apply only to a specific building; neither the inspector nor the authority will accept a template design of another building.

Do you design lightning protection on its own, without the electrical design?

Yes – for new buildings, roof renovations, retrofitted PV and for battery storage and transformer stations. It is more economical, however, to solve lightning protection together with the electrical installation or the power plant, because earthing and surge protection are linked.

How long does the design take?

For a family house a matter of days from receiving the input documents, for an industrial site a matter of weeks – it depends on the roof area, the equipment and whether drawings of the building are available.

Planning a similar project?

Send us the site and your intent. We reply within 48 hours.

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