Fire safety in roofing has moved from a background consideration to a central specification issue over the past several years, and for good reason. Understanding what current UK regulations actually require — and what’s changed since Grenfell — matters for anyone responsible for a commercial building’s roof, whether it’s a new installation, a refurbishment, or ongoing maintenance decisions, and increasingly forms part of the due diligence expected by insurers, lenders, and building control bodies alike.

Why this has become a bigger issue

The Grenfell Tower fire in 2017 fundamentally changed how fire safety in building envelopes — cladding and roofing alike — is regulated and scrutinised in the UK. While the most severe regulatory changes have focused on high-rise residential buildings, the ripple effects have reached commercial roofing specification more broadly, with clients, insurers, and building control bodies now paying far closer attention to the fire performance of materials that might previously have been chosen primarily on cost and thermal performance. This shift has been particularly notable in how insurers now assess commercial property risk, with some now specifically requesting evidence of insulation type, fire classification, and detailing as part of underwriting for larger commercial roofs.

The regulatory framework in brief

Building Regulations Part B (Fire Safety) sets out the core requirements for how buildings must resist and limit fire spread, including provisions relevant to roof coverings and, where applicable, roof insulation. The Building Safety Act 2022, introduced directly in response to Grenfell, brought a stricter regulatory regime for higher-risk buildings and reinforced a broader principle that’s increasingly applied across commercial construction generally: those responsible for a building’s safety must be able to demonstrate — with evidence — that fire safety has been properly considered, not simply assumed.

For buildings over 18 metres, restrictions on combustible materials in the external wall system introduced after Grenfell have particular relevance where roofing details meet external walls or parapets, since roof-to-wall junctions are precisely the sort of detail that can inadvertently introduce combustible materials into an otherwise compliant wall system if not carefully specified. The “golden thread” of building safety information, a concept introduced through the Building Safety Act, also has implications for roofing — building owners are increasingly expected to maintain accurate, accessible records of what materials were used, where, and to what specification, throughout the building’s life, not just at the point of construction.

Reaction to fire vs fire resistance: two different things

A source of genuine confusion in roofing fire safety is the difference between “reaction to fire” and “fire resistance.” Reaction to fire (classified under BS EN 13501-1) describes how a material behaves if it catches fire — how much it contributes to flame spread, smoke, and burning droplets, and is classified on a scale from A1 (non-combustible) through to F. Fire resistance describes how long a construction can hold back fire and prevent it spreading through to another space, typically expressed in minutes (30, 60, 90, 120) and tested as a complete system rather than an individual material.

Both matter for roofing, but they’re tested and classified differently, and a material can perform well on one measure while requiring careful specification on the other — insulation materials in particular need to be assessed on both counts, not just whichever figure looks best on a data sheet, since a specification chosen purely on the strength of a favourable reaction-to-fire classification, without considering the fire resistance of the assembled roof buildup, can leave a genuine gap in overall fire performance.

Insulation: where fire safety gets specific

PIR insulation, the most widely used rigid insulation board in UK flat and metal roofing, is not banned in the UK and remains a legitimate, widely specified product — a common point of confusion given its association with the type of foam insulation implicated in some cladding fire investigations. However, its fire classification (typically Class E or F to BS EN 13501-1, commonly described as “combustible”) means it requires careful system-level specification, particularly around detailing, compartmentation, and how it interacts with the wider roof buildup, rather than being specified in isolation.

Non-combustible alternatives — mineral wool and cellular glass being the most common — achieve better fire classifications (typically A1 or A2) but typically require greater thickness to match PIR’s thermal performance, creating a genuine specification trade-off between fire safety margins and roof buildup thickness, weight, and cost. Some manufacturers have responded with hybrid or enhanced-classification PIR products designed to offer improved fire performance while retaining much of PIR’s thermal efficiency, and it’s worth discussing these options where fire risk is a particular concern for a given building or use.

What this means for roof coverings and membranes

External fire performance of roof coverings — how a roof responds to fire from an external source, such as a firebrand landing on the surface — is governed by testing to BS 476-3 or the newer BS EN 13501-5 standard, with roofs classified according to their resistance to external fire spread. This is particularly relevant where roofs are close to boundaries, adjacent buildings, or where multiple roof areas connect across a large industrial or retail site, since fire spread across a connected roofscape is a genuine risk that specification needs to account for, particularly on retail parks and industrial estates where units share party walls or closely adjoining roof areas.

Compartmentation at roof level — the use of fire breaks, cavity barriers, and correctly detailed junctions between roof sections — is an area that’s easy to overlook once a roof is complete and covered, but is fundamental to limiting how far a fire can spread across a large roof area before it’s brought under control.

Solar panels and fire risk: a growing consideration

As solar PV installations on commercial roofs increase, so has scrutiny of the fire risk they introduce — DC cabling, inverters, and the way panels interact with the roof buildup beneath them all need proper fire risk consideration, not just structural loading and waterproofing. Panels mounted without adequate isolation from the roof’s fire-rated layers, or installed with poor access routes for fire services, can meaningfully compromise a roof’s overall fire safety even where the roof covering itself is well specified. Fire service access routes, clear zones around roof edges and rooflights, and correctly isolated DC cabling runs are all details that need to be considered at the design stage of a solar installation, not added as an afterthought once panels are already specified.

What this means in practice for a refurbishment or new roof

Fire safety can no longer be treated as a secondary consideration bolted onto a roofing specification chosen primarily for cost and thermal performance. It needs to be considered from the outset, particularly for insulation choice, detailing at roof edges and junctions, and how any additional installations — solar panels, plant equipment, rooflights — interact with the roof’s fire performance as a complete system. For refurbishment projects in particular, it’s worth treating fire safety review as a standard part of the specification process, rather than assuming that because the existing roof was compliant when installed, a like-for-like replacement will automatically remain so under current standards.

Getting it right

At RMLFS, fire safety is built into how we specify roofing systems from the start, not treated as an afterthought, and we work with manufacturer-approved, correctly classified materials and detailing appropriate to each building’s risk profile and regulatory requirements.