Lightning and Surge Protection: Which Beliefs Cost Owners Equipment

Lightning protection is misunderstood as a rod on the roof. The damage owners actually suffer comes through power and data cables, and is prevented differently.

A lightning protection system gives a strike a controlled path to earth so it does not travel through the structure. Surge protection is a different job: it limits the voltage transients that arrive along power, data and telephone cables, from distant strikes as well as from switching events on the network. Most equipment losses in buildings come from the second problem, which is why a roof installation alone leaves owners surprised.

How to test a claim like this

Separate three questions that get mixed together. Does the structure need a lightning protection system, which is a risk assessment based on location, height, use and exposure? Is the earthing and bonding of the building adequate and tested, which is a basic electrical safety matter regardless of lightning? And are sensitive loads protected by surge devices at the right places, which is an equipment protection question? Any proposal that answers only one of these and prices it as complete protection is incomplete.

Myth 1: A metal rod on the roof protects everything inside the building.

Reality: An air termination gives a strike a preferred attachment point and a conductor path to earth. It does nothing about the voltage transients induced on cabling inside and around the building, which is how most electronics are damaged. Protection of equipment requires coordinated surge devices at the incoming supply, at distribution boards and at sensitive loads.

How to check it yourself: Ask whether the design includes surge protective devices, and where each one sits in the distribution.

Myth 2: A building only needs lightning protection if lightning is common locally.

Reality: The decision follows a risk assessment that weighs strike probability against consequence. A tall isolated structure, a building with occupants who cannot evacuate quickly, a site with flammable storage or a facility whose downtime is costly may justify protection even where storms are infrequent. Equally, a low building in a dense area may not require a system at all.

How to check it yourself: Ask for the risk assessment that justified the decision, in either direction, as a document.

Myth 3: Earthing is something the electrician handled during construction.

Reality: Earth electrode resistance changes with soil moisture, corrosion and later excavation work. Bonding connections loosen, get painted over or are removed during refurbishment. The earthing system is a maintained asset with a measurable value, and the measurement should be repeated periodically and recorded rather than assumed from a certificate issued years ago.

How to check it yourself: Request the most recent earth resistance measurement with its date and the test method used.

Myth 4: One surge protector at the main panel covers the whole building.

Reality: Surge protection is coordinated in stages. A device at the origin of the installation handles the largest energy, while devices further down reduce the let through voltage to a level sensitive equipment can tolerate. Distance and cable length between stages matter. A single device at the main board leaves equipment at the far end of long circuits exposed.

How to check it yourself: Ask for a single line diagram showing each surge device and the loads it is intended to protect.

Myth 5: Data and signal cables do not need protection.

Reality: Transients enter readily along network cabling, camera runs, telephone lines, antenna feeds and any cable that leaves the building. Equipment is frequently destroyed through its data port while its power supply survives. Any cable that runs between buildings or up an external wall deserves specific attention, including surge devices and proper bonding at both ends.

How to check it yourself: List every cable that leaves the building envelope and confirm what protects each end.

Myth 6: Once installed, lightning and surge protection is maintenance free.

Reality: Surge devices are consumed by the events they absorb, and many have a status indicator that shows when the device has reached end of life. Conductors corrode, especially in coastal air, and fixings loosen. A protection system that has never been inspected since installation may be providing a false sense of security while several of its components are dead.

How to check it yourself: Add a visual inspection of indicators, conductors and bonds to the planned maintenance schedule.

What this changes in your decision

• Commission a risk assessment before accepting or rejecting a structural lightning protection system.
• Treat equipment protection as a separate, coordinated surge design with devices at defined points.
• Measure and record earth resistance periodically rather than relying on a construction certificate.
• Protect both ends of every cable that crosses between buildings or runs externally.
• Inspect surge device indicators and down conductors as part of routine maintenance, with dated records.

Domira works on buildings that already exist: surveying what is installed, specifying the systems that have to be replaced, and running maintenance and refurbishment work around the people using the property. Tell Domira which asset you are responsible for and we will say what we would inspect first.