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Lightning protection
testing

Annual inspection, certification and remedials.

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What a test involves

A lightning protection test is a visual inspection, a continuity test and an earth resistance measurement, recorded against the previous set of readings. The visual inspection finds corrosion, damage, loose fixings and components that have gone missing. The continuity test proves the current still has an unbroken path from the roof to the ground. The earth resistance measurement shows whether the ground can still take it.

The comparison with previous readings is the part that gets skipped and the part that matters. A single reading tells you the system passed today. A run of readings tells you which electrode is drifting and will fail in two years, which is the information you need to budget.

We test systems we installed and systems installed by other contractors. If we find the system cannot be tested properly, usually because test clamps were never fitted or have been covered over, we will say so rather than issuing a certificate that does not mean anything.

You receive

  • Test certificate for the system.
  • Recorded earth resistance readings for each test point.
  • Continuity results across joints and down conductors.
  • A written list of defects, in risk order.
  • A separate quotation for any remedial work, so it is not hidden in the test fee.
  • A log book entry, or a new log book if there is not one.

Why the certificate matters

Regulation 4(2) of the Electricity at Work Regulations 1989 requires electrical systems to be maintained so as to prevent danger. A lightning protection system is an electrical system, so once you have one, keeping it in working order is a legal duty rather than good practice.

Separately, most commercial insurers ask for a current test certificate, and some will ask for it at renewal or after a claim. A gap in the record is the problem, not the condition of the conductors.

Testing frequency explained

How often

BS EN 62305-3 sets maximum intervals by protection class. Class I and II systems take a visual inspection every year and a full inspection every two years. Class III and IV systems take a visual inspection every two years and a full inspection every four. Structures with a risk of explosion are inspected more frequently.

UK practice is a full test every eleven months, which keeps you inside a twelve month insurance window and rotates the test through the seasons so ground conditions are not always sampled in the same weather. Additional tests are needed after a known strike, after work that alters the roof or the elevations, and after anything is added to the roof that is not bonded in.

Common questions

How do you test a lightning conductor?

A full test has three parts. A visual inspection of the whole system for corrosion, damage, loose fixings and missing components. A continuity test across every joint and along each down conductor. An earth resistance measurement at each test clamp and for the earth termination system as a whole. Readings are recorded against the previous test so deterioration shows up as a trend rather than a surprise.

What is the test point for lightning protection?

The test point, or test clamp, is the accessible joint between a down conductor and its earth electrode. Opening it lets an engineer measure that electrode on its own rather than measuring the whole system in parallel. If test clamps were not fitted, or have been buried by later building work, individual electrodes cannot be measured and the system cannot be properly certified.

What earth resistance reading should I expect?

BS EN 62305-3 recommends the earth termination system as a whole comes in at 10 ohms or less. Individual electrodes measured at their test clamps will read higher than the combined figure, which is normal. Soil type, moisture and the season all move the number, which is why the readings are compared with previous tests rather than judged in isolation.

Can an electrician test lightning protection?

A general electrician is not the right person for this. Testing a lightning protection system means assessing it against BS EN IEC 62305-3, working at height on the outside of the building, and issuing certification an insurer will accept. It needs a lightning protection specialist with the right test equipment and the right competence record.

What is the British standard for lightning protection testing?

BS EN IEC 62305, and specifically Part 3, which covers inspection and maintenance of the system along with its physical design. It replaced BS 6651, which was withdrawn in 2008. The current edition of the 62305 series was published in 2024.

What happens if the system fails?

We record what failed, why, and what it needs, then quote the remedial work separately so you can see it rather than finding it buried in a test fee. Common failures are corroded clamps, conductors damaged by other trades, missing bonds to newly installed roof plant, and earth electrodes that have degraded. Most are repairable without redesigning the system.

Test due?

Tell us the site address and roughly when it was last tested. If you have the last certificate or log book, send that too and we will pick up from the previous readings. Call 01892 667258.

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