Maintenance · Guide

Twenty-one loudspeakers or one zone: when voice alarm work stops being a repair

British Standard BS 5839-8:2023 draws the line between repair and modification. Here is where it falls, and who signs the certificate when you cross it.

By Nigel Williams · Published 16 October 2026

The Greeks argued about a ship. Replace one rotten plank and it is plainly the same ship. Replace every plank, one at a time, and is it still the ship that left harbour?

Philosophers never settled it. For voice alarm systems, the code of practice gives a working answer, and it comes with a number.

A repair puts the system back as it was

BS 5839-8:2023 handles the two kinds of work in separate clauses. Repair of faults or damage sits in Clause 41.2. Modification sits in Clause 41.3.

Repair restores the system as designed. A failed amplifier swapped for the same model, a dead power supply replaced, a battery set renewed: the zoning does not change and neither do the as-fitted drawings. That is why we treat like-for-like replacement as repair. The code's recommendations for repair are about response and records: a call-out arrangement with normal attendance within 8 h, on a 24 h basis, and every fault and repair recorded in the logbook (BS 5839-8:2023, Clause 41.2).

A modification changes what the system is

A modification is different in kind. It changes the system the original design described, whether the work is done on site or remotely (Clause 41.3).

The code recommends five things when that happens:

• the person responsible is competent in voice alarm design, knows the standard and the installed system, and has the as-fitted drawings (41.3 a))
• premises management agrees the modification in writing (41.3 b))
• everything known to be affected is tested, with particular attention to power supply and battery capacity, amplifier rating, loudspeaker-circuit fault monitoring and software changes (41.3 c))
• the as-fitted drawings and records are updated (41.3 d))
• a modification certificate is issued (41.3 e))

Notice who carries those responsibilities. It is the organisation doing the modification, not whoever happens to service the system next.

Where the line falls

Note 3 to Clause 41.3 gives examples of changes for which a modification certificate is generally necessary. Any one of them is enough:

• more than 5 % of the loudspeakers or voice sounders added or removed
• any emergency microphone or power amplifier added or removed
• any change to the number of emergency loudspeaker zones
• any change at the control equipment that alters the agreed cause and effect

Take a building with 400 loudspeakers. Five per cent is 20. Add 20 and you are at the threshold; the 21st takes you past it.

Now look at the third line. Split one zone into two and you are past the threshold at once, without adding a single loudspeaker. The count that matters most is not always the one people watch.

A note is informative rather than a numbered recommendation, and the wording is "generally necessary". That is a guide for judgement, not a licence to stop counting at 20.

Three ways it goes wrong

The fit-out that adds "only a few". A tenant fit-out adds six loudspeakers to a ceiling. Nobody counts it as a modification. Three fit-outs later, the zone carries a load the amplifier was never rated for, and no test under 41.3 c) ever checked it. We read every piece of work against the as-fitted drawings, so a run of small jobs stays visible.

The remote software change. A controller update or a change to the message routing, pushed remotely, is still a modification: Clause 41.3 covers remote work as well as site work. If it alters the agreed cause and effect, Note 3 says a modification certificate is generally necessary.

The certificate nobody issues. The fit-out contractor finishes, the maintainer was never told, and the drawings still show the old layout. The next person to change anything is working from a plan that is wrong.

"Our contractor says it's only a few loudspeakers"

They may be right. Count them against the as-fitted drawings, and check the other three lines of Note 3 before agreeing.

If it is a modification, the contractor doing the work carries the 41.3 responsibilities, including the certificate. If another firm, such as your maintainer, will do the testing, write down who is responsible for each part before the work starts. A modification certificate signed by one firm on another's test results is workable, provided the split is on paper first.

Two examples

A new meeting suite. Twelve loudspeakers added to an existing zone in a building with 300. Five per cent is 15, so this is under the loudspeaker threshold. But if the extra load needs a larger amplifier, an amplifier has been added, and that line of Note 3 applies on its own.

A like-for-like amplifier swap. A failed amplifier replaced with the same model, at the same rating, on the same circuits. Nothing in the design has changed. That is repair under 41.2, recorded in the logbook, with no modification certificate needed.

In short

• Repair restores the system as designed (Clause 41.2). Modification changes it (Clause 41.3).
• A modification certificate is generally necessary past 5 % of loudspeakers, or with any added or removed amplifier or emergency microphone, any change in the number of emergency zones, or any change to the agreed cause and effect (41.3, Note 3).
• The firm doing the modification tests it, updates the drawings and issues the certificate (41.3 c) to e)).
• Premises management agrees the work in writing first (41.3 b)).

Replace one plank and it is a repair. Change the shape of the ship and someone has to sign for it.

Next step. Before your next fit-out, find the as-fitted drawings and count the loudspeakers in the affected zones. If the work could cross any line in Note 3, ask the contractor in writing who will issue the modification certificate. ProAudium carries out modification testing and certification across London and the South East: contactus@proaudium.com or 01273 034630.