Solar, Sprinklers and Your Insurer: The RC62 Guide for Warehouse Roofs

In short: rooftop solar and warehouse sprinklers coexist safely when the array is designed to LPC / RISCAuthority RC62 guidance - clearances from sprinkler zones and firewalls, DC isolation and rapid shutdown - and the building’s insurer signs off the design before fabrication. Insurer pre-design review should be a standard step on every warehouse solar project, not an afterthought.

Of all the objections that stall a warehouse solar project, the one that kills it silently is fire and insurance. A logistics director will happily debate payback, self-consumption and grid capacity - but “will this invalidate our cover?” is rarely said out loud, and it is the question that most often parks a proposal indefinitely. This guide is about closing that gap: what the fire-safety framework actually says, why your insurer cares, and how a properly designed array turns the silent objection into a signed-off, non-issue.

Why fire and insurance sit at the centre of warehouse solar

A distribution shed is a concentrated, high-value asset. Racking runs floor-to-ceiling, stock density is high, and a fire that gets established is expensive and slow to control. That is exactly why modern warehouses are sprinklered - and why property insurers underwrite them on the assumption that the roof, the compartmentation and the fire-suppression system all work as designed.

Rooftop photovoltaics introduce three things insurers scrutinise: a new electrical system on the roof that generates DC voltage in daylight and cannot simply be “switched off” at the meter; physical hardware - panels, rails, cabling and inverters - sitting above the roof membrane and, potentially, across sprinkler zones and firebreak lines; and a maintenance and access consideration for the fire and rescue service if they ever need to work on that roof during an incident.

None of these is a reason not to install solar. They are reasons to design it properly and to bring the insurer in early. The framework that governs how you do that in the UK is RISCAuthority’s RC62.

What is LPC / RISCAuthority RC62?

RC62 is the recognised UK fire-safety design guidance for rooftop and ground-mounted solar PV, published by RISCAuthority (RC62 rooftop PV guidance), the insurer-backed research scheme that sits alongside the Loss Prevention Council (LPC) rules to which most UK commercial property insurers refer. When an underwriter asks whether your array is “designed to RC62”, they are asking whether it follows the recognised risk-control document for solar on commercial buildings.

RC62 does not exist to make solar difficult. It exists so that a PV system does not increase the fire risk of the building it sits on, does not compromise the fire-suppression already in place, and does not create new hazards for anyone who has to work on the roof. It is written from the insurer’s point of view, which is precisely why designing to it is the fastest route to cover being confirmed rather than questioned.

The rest of this guide covers the four principles RC62 addresses on a sprinklered warehouse. We describe the principles rather than quote exact figures: the specific clearances and dimensions are set out in the current RC62 document, and a competent designer works to that live version rather than to a number remembered from an older edition.

1. Clearances from sprinkler zones and firebreaks

The most warehouse-specific principle is spacing. A sprinkler system is engineered to detect and suppress a fire within defined zones; the roof is also divided by compartment lines and firebreaks that are meant to stop fire spreading across a large single-span building. An array that ignores those lines can, in a worst case, bridge them.

RC62 addresses this by requiring the PV layout to respect the building’s existing fire strategy - leaving defined clearance around sprinkler infrastructure and maintaining firebreak separations so that a section of the roof can still be isolated. In practice this means the panel layout is built around the fire-protection design and access routes, not the other way round. This is also why “just fill the roof” is the wrong instinct on a warehouse for fire reasons as well as economic ones: the usable area is defined by clearances, plant, rooflights and firebreaks long before it is defined by the roof edge.

2. DC isolation

A solar array is live whenever there is daylight on the panels, regardless of whether the building’s mains supply is on. That is the single fact that changes the electrical risk picture for a firefighter or a maintenance engineer.

RC62 addresses this through DC isolation: the ability to break the DC circuits so that live cabling is not running unmanaged across the roof and down into the building during an incident. Good design keeps DC cable runs short and well-labelled, isolators accessible, and the routing clear of the areas the fire service is most likely to need. The goal is that the electrical system is understood and controllable, not an unknown hazard on top of the fire the crew is already dealing with.

3. Rapid shutdown

Closely related to isolation is rapid shutdown - the ability to bring the array to a safe, de-energised state quickly at or near the panels, rather than only at the inverter. This limits the length of cable that remains live once the system is shut down and reduces the risk to anyone working on or near the roof during an emergency.

Whether rapid shutdown is delivered at module level, at string level or through the inverter architecture is a design decision, but the principle RC62 is concerned with is straightforward: the roof should be able to be made electrically safe fast, and everyone who might need to do it should know how.

4. Firewalls and compartmentation

A large warehouse is often a single vast volume broken up by compartment walls and firebreaks precisely so that a fire in one area does not become a fire across the whole footprint. Rooftop PV must not undermine that. RC62’s principle here is continuity: the array respects compartment lines, maintains the separations designed into the building, and does not create a continuous combustible or electrical bridge across a break that is there to stop fire spread.

This is why the fire strategy for the building - not just the roof plan - belongs on the designer’s desk from day one.

Why insurers (Allianz, AIG, Zurich, FM Global) care

UK commercial property insurers underwrite warehouses on a detailed risk assessment, and the major players active in this space - Allianz, AIG, Zurich and FM Global among them - each have their own rooftop-PV criteria. They are not hostile to solar; many actively encourage on-site renewables. But they will want to see that a new system on the roof has not changed the risk they priced.

From an underwriter’s chair, an array designed and documented to RC62 is a known quantity: it respects the sprinkler and compartmentation design, it can be isolated and shut down safely, and it has been assessed against the building’s fire strategy. An array that has been “roof-filled” by a generalist installer with no reference to RC62 or to the building’s insurer is an unknown - and unknowns get priced, excluded, or discovered at claim time.

The practical risk of getting this wrong is rarely an outright refusal to insure. It is subtler: a premium loading, a condition attached to the policy, a reduced sum insured, or a coverage dispute if a claim arises and the insurer was never told about the array. Any of those can turn a good solar business case into a bad one after the fact. Engaging the insurer before design removes that risk entirely.

The pre-design review: the step that removes the objection

The single most important thing this guide recommends is procedural, not technical: get the insurer’s sign-off on the design before anything is fabricated.

A pre-design insurer review means the underwriter (or their appointed risk engineer) sees the proposed layout, the mounting method, the DC isolation and shutdown approach, and how the array sits relative to the sprinkler zones and firebreaks - while it is still a drawing that can be changed cheaply. Any concern is resolved on paper. By the time panels are ordered, the insurer has already agreed the design is acceptable.

This sequencing matters because the alternative - installing first and asking the insurer afterwards - is where cover disputes are born. On a well-run warehouse project the order is:

1. Roof, structural and (where relevant) asbestos survey.
2. Load-led system design from half-hourly meter data, laid out to respect the fire strategy.
3. RC62-aligned fire-safety review of the layout.
4. Insurer pre-design review and sign-off.
5. Fabrication and installation.
6. Post-install documentation pack handed to the insurer and site team.

Making step 4 a fixed gate, not an optional extra, is what converts “will this affect our insurance?” from a project-stopping worry into a box already ticked.

Roof-membrane compatibility and mounting

Fire and insurance are not only about electricity and clearances - they are also about the roof itself. Most modern UK logistics stock is a standing-seam or trapezoidal metal roof on a clear-span steel-portal frame, and how you fix to it matters for both the roof warranty and the fire/insurance position.

Non-penetrative clip-fix mounting - clamping to the standing seam rather than drilling through the membrane - preserves the roof manufacturer’s warranty and avoids introducing new penetrations that could compromise weather-tightness or fire performance. Where a roof needs a ballasted approach, wind loading is designed to BS EN 1991-1-4 (Eurocode 1) wind loading principles and the additional dead load is checked by a structural survey, typically required on arrays over roughly 1,000 m². On any roof built before 2000, an asbestos management survey comes first. Getting the mounting and membrane right keeps two separate warranties intact - the roof’s and the PV system’s - and keeps the insurer comfortable that the building envelope has not been degraded.

How good design removes the silent objection

Put the pieces together and the fire/insurance question answers itself:

• The array is laid out to RC62 - clearances from sprinklers and firebreaks, compartmentation respected.
• It can be isolated and rapidly shut down, so it is a controllable system, not an unknown hazard.
• The roof membrane and warranty are protected by the right mounting method.
• The insurer has signed off the design before fabrication, so cover is confirmed, not questioned.

That is a project an underwriter recognises and a logistics director can approve without a nagging worry in the background. Competitor proposals routinely skip this entirely - it is one of the clearest gaps in warehouse-solar sales, and it is the one that quietly loses deals. Treating insurer engagement as a standard step, on every project, is what separates a specialist warehouse installer from a generalist filling a roof.

This is particularly acute for 3PL and contract-logistics operators, who carry stringent customer and audit obligations on top of their own cover, and for bonded, customs and Freeport warehousing, where controlled access and HMRC permissioning make an insurer-agreed, well-documented roof design essential rather than optional.

The bottom line

Sprinklers and solar are not in conflict. The conflict only appears when an array is designed without reference to the building’s fire strategy and installed without the insurer’s knowledge. Design to LPC / RISCAuthority RC62, respect the sprinkler zones, firebreaks and compartmentation, build in DC isolation and rapid shutdown, protect the roof membrane, and - above all - get the insurer’s pre-design sign-off before fabrication. Do that, and the fire/insurance question stops being a silent objection and becomes a line item you have already resolved.

If you are weighing a rooftop array and want the fire, insurance and roof-warranty side handled properly from the outset, that is exactly how we work: load-led design, RC62-aligned layout, insurer pre-design review as standard. See what a system would cost on your roof on our cost page, check the grants and tax reliefs that apply to warehouse solar, and when you are ready, request a quote - we will build the fire and insurer sign-off into the process from day one.

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The figures and framework references in this guide are indicative and planning-grade. Fire-safety clearances and design specifics must be taken from the current RISCAuthority RC62 document and confirmed with your building’s insurer. This article is general guidance, not fire-engineering or insurance advice for a specific site.