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The most dangerous fire safety failures in UK buildings are not the ones that trigger an alarm.
They are the ones that don’t. The ones that exist silently, invisibly, in the fabric of the building itself, in the walls, floors, ceiling voids, and service risers that were fire-rated when they were built, and are no longer fire-rated now.
The scale of the consequence when compartmentation fails is not theoretical. Fire and rescue services reported 380 fire-related fatalities in the UK in 2011-12. Of those, 130 deaths were attributed to a lack of fire compartmentation. Not to a failure of detection. Not to a delayed response. To the failure of the barriers that should have contained the fire and protected the escape routes that people’s lives depended on.
Fire compartmentation is the technical term for the system of fire-rated barriers that divides a building into separate zones. When a fire occurs in one compartment, those barriers are supposed to contain it, preventing the spread of fire and smoke to adjacent areas and providing the time for evacuation that the building’s fire strategy depends on. In a well-maintained building with intact compartmentation, a fire in one office suite does not reach the stairwell. A fire in a plant room does not spread to the floors above it. The barriers hold.
In most buildings I survey, the barriers would be unlikely to hold. Not because they were poorly built. Because they have been compromised repeatedly, incrementally, by the routine activity of maintaining and adapting a working building, and nobody has noticed.
What compartmentation is
To understand why this happens, it helps to understand what fire compartmentation involves in practice.
A compartment wall or floor is a construction element (masonry, concrete, plasterboard on a steel frame, or a specialist fire-rated system) that has been tested and certified to resist fire passage for a specified period. Common ratings are 30 minutes, 60 minutes, and 120 minutes. That rating is only valid for the construction as it was tested and certified. Any opening, penetration, or modification to that element must be reinstated to the same fire rating using certified materials and methods.
That requirement sounds straightforward. In practice, buildings accumulate penetrations at a rate that most facilities teams do not track.
Every cable tray that passes through a fire-rated wall. Every pipe that runs from a plant room through to an adjacent corridor. Every duct that carries air from one compartment to another. Every opening cut for a new service run, a new network cable, a new sprinkler head, a new electrical conduit. Each of those penetrations must be sealed with an intumescent or fire-rated seal that restores the original fire resistance of the element. In a building that has been in use for ten or twenty years, the number of unsealed or inadequately sealed penetrations in fire-rated elements can run into the hundreds.
And that is before you consider fire doors, which are themselves a compartmentation element, or dampers in ductwork that should close automatically to prevent fire spread through the ventilation system, or fire stopping in ceiling voids that has been displaced by contractors accessing services above the ceiling line. Management and recording of these ongoing works are key to maintaining the integrity of the building.
Why the failures accumulate invisibly
The reason compartmentation failures are so common is structural rather than negligent. It is simply the way buildings are maintained.
When an electrician runs a new cable through a fire-rated wall, their job is to run the cable. The fire stopping is not their primary responsibility, and in many cases it is not in the scope of work they have been contracted to do. The facilities manager who commissioned the work is focused on the electrical outcome. The fire stopping gap may not be noticed at all. It is above a ceiling tile, or behind a service panel, or in a riser cupboard that nobody looks inside between service visits.
When a plumber installs a new pipe through a floor slab, the penetration may be sealed immediately, partially, or not at all, depending on the plumber’s awareness of fire stopping requirements, the availability of the correct materials, and whether the work is being inspected. In most commercial buildings, it is not being inspected.
Over time, a building that passed its fire risk assessment three years ago may have accumulated dozens of new penetrations. None of them individually catastrophic, all of them individually addressable, that collectively represent a material failure of the compartmentation strategy that the fire risk assessment assumed was intact.
There is a further factor worth naming. As responsibility for fire door compliance and passive fire protection passes down from building owners to building managers, facilities teams, and contracted maintenance providers, the detailed technical knowledge required to identify failures can become diluted. This is true not just of fire doors, but of the wider passive fire protection estate, including dampers, fire stopping, compartmentation. The system was specified by a fire engineer, installed by a specialist contractor, and certified at practical completion. The person now responsible for maintaining it may have strong general facilities knowledge without the specific training to identify the difference between a penetration that looks sealed and one that is sealed to the required standard. That knowledge gap is not a criticism of the people involved, it is a structural feature of how maintenance responsibility is transferred, and it is one of the reasons independent specialist inspection matters.
This is the part of the conversation that surprises most facilities managers I work with. They understand that fire doors need to be inspected. They understand that fire alarms need to be tested. They do not always understand that the walls and floors of their building are also fire safety assets that degrade with use and that the degradation is invisible unless someone looks.
The Building Safety Act 2022 has sharpened the legal context for compartmentation significantly. The Act introduced the concept of the Principal Accountable Person (the entity legally responsible for the structural and fire safety of higher-risk residential buildings) and placed specific duties on them in relation to the building’s passive fire protection.
For higher-risk buildings (those over 18 metres or 7 storeys), the Act requires a Building Safety Case — a comprehensive document demonstrating that fire and structural risks are being actively managed. Compartmentation integrity is a core element of that case. A building whose compartmentation has not been formally surveyed and documented cannot produce a credible Building Safety Case.
For buildings not within the higher-risk category, the Regulatory Reform (Fire Safety) Order remains the primary legislative framework. The RRO requires the Responsible Person to maintain the fire safety measures in the building in an effective state. Compartmentation is a fire safety measure. A Responsible Person who has not arranged for compartmentation surveys following building works, or who cannot demonstrate that penetrations have been sealed to the required standard, is not meeting their legal obligation under the Order.
The Fire Safety Act 2021 also clarified that the structure and external walls of a building (including compartmentation elements) are within scope of the fire risk assessment for multi-occupied residential buildings. This removed a longstanding ambiguity that had allowed some freeholders and managing agents to treat compartmentation as outside the scope of their fire safety obligations.
The practical implication is this: in 2026, there is no longer a defensible argument that compartmentation is someone else’s responsibility, or that it only matters for new buildings, or that a general fire risk assessment covers it adequately. It does not. A fire risk assessment tells you whether your active fire detection and warning systems are functioning. It does not tell you whether your compartment walls are intact. Those are different questions that require different expertise.
What a compartmentation survey involves
A fire compartmentation survey (sometimes called a fire compartmentation audit or passive fire protection survey) is a systematic inspection of the fire-rated elements of a building carried out by a qualified professional.
It is not a desk-based exercise. It requires physical access to ceiling voids, service risers, plant rooms, roof spaces, and any other area where fire-rated elements are present or where service penetrations are likely to have been made. In practice, this means intrusive inspection (i.e. lifting ceiling tiles, opening access panels, inspecting the areas behind and above the surfaces that are visible from the building’s occupied spaces).
A thorough survey will document every fire-rated element in scope, every penetration identified in those elements, the condition of any fire stopping present, any evidence of displacement, damage, or incorrect materials, and any areas where access was not possible and re-inspection is required. These can be either non destructive or destructive in nature. If there are reasonable doubts regarding the hidden aspects of compartmentation inspectors may be asked or wish to remove building fabric to visually identify any potential problems. This can include things like the removal of fire door architrave and cutting small inspection holes in walls.
The output is a schedule of findings. Typically organised by element type, location, and severity, with photographic evidence of each deficiency and a recommendation for remediation. Deficiencies are usually graded by priority: immediate action required, action required within a specified period, and monitor and review.
For a building of any significant size or age, the survey findings are almost always more extensive than the building’s management team expects, because compartmentation failures are genuinely invisible until someone specifically looks for them.
The cost of finding out the hard way
The alternative to a compartmentation survey is discovering the failures through the mechanism they were designed to prevent.
When a fire spreads beyond its compartment of origin, the investigation that follows will establish why. Surveyors from the fire investigation team, the insurer, and the regulatory authority will examine the fire-rated elements that were supposed to contain the spread. They will find the unsealed penetrations, the displaced fire stopping, the damper that was not maintained. They will establish when those failures occurred and whether they were known or knowable.
The consequences fall on the Responsible Person. Enforcement action under the Regulatory Reform (Fire Safety) Order. Prosecution under the Building Safety Act for failures in higher-risk buildings. Civil liability for loss and injury arising from the spread of fire beyond what should have been its compartment of origin. Insurance claims complicated or invalidated by evidence that the building’s fire protection measures were not maintained in an effective state.
None of those outcomes are hypothetical. The Grenfell Tower Inquiry which examined, among many other things, the failure of fire stopping and compartmentation in the building has fundamentally changed how regulators, insurers, and the courts approach passive fire protection failures. The expectation of proactive, documented, evidenced inspection of compartmentation elements is now firmly established.
Where to start
For most buildings, the starting point is understanding what compartmentation elements exist and when they were last formally assessed.
If your building was constructed or substantially refurbished in the last five years and you have a detailed fire safety file that includes compartmentation drawings, fire stopping specifications, and completion certificates for all penetrations, you are in a stronger position than most. You still need to consider whether any building works or service installations since completion have compromised what was certified.
If your building is more than five years old, has undergone any degree of fit-out, refurbishment, service upgrade, or change of use, and you do not have documented evidence of compartmentation surveys carried out since those works, the realistic assumption is that there are deficiencies. On many occasions I have witnessed contractors making use of pink PU foam to fill breaches in compartment walls. In most cases this is not an approved method. The question is not whether a survey will find anything (it almost certainly will). The question is whether you would rather find it proactively, with time to address it systematically, or reactively, in circumstances over which you have no control.
Evolution Life Safety Systems carries out fire compartmentation surveys for building owners, facilities managers, and responsible persons across the UK. We are BAFE-accredited, and our compartmentation surveys are carried out in accordance with current fire risk assessment guidance under PAS 79-1:2020 for non-domestic premises. We produce survey reports with individual element records, photographic evidence, and prioritised remediation schedules.
If you would like to understand what a compartmentation survey involves for your building, and what it is likely to find, I am happy to have that conversation. The starting point is always an honest assessment of where you are.
Not always. A standard fire risk assessment may identify visible concerns, but it will not usually confirm whether compartment walls, ceilings, service risers, or concealed voids remain intact. A dedicated compartmentation survey is required to assess passive fire protection properly.
A fire compartmentation survey is a detailed inspection of a building's passive fire protection measures. It typically involves accessing ceiling voids, risers, plant rooms, and other hidden areas to identify breaches, damaged fire stopping, and other compartmentation defects.
There is no universal inspection interval for every building. However, compartmentation should be reviewed following refurbishment works, service installations, changes of use, or whenever there is uncertainty about the condition of the building's passive fire protection.
Zone plans, logbooks, design certificates, cause-and-effect matrices, and records of any variations all need to be in place and available.
If your building is more than five years old, has undergone refurbishment, fit-outs, service upgrades, or changes of use, and you do not have recent documented evidence of compartmentation inspections, a survey is likely to be recommended.
Speak to our Life Safety Systems team today to arrange a compartmentation survey and gain a clear understanding of the hidden fire safety risks within your building.
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Sam Burgess is one of our account managers responsible for system sales in the Life Safety Systems division at Evolution, part of Evolution Security Group. With over 20 years of experience in fire detection and alarm systems across commercial, healthcare, education, and residential care sectors, Sam works with clients across the UK to design, install, and maintain systems that meet both regulatory requirements and the practical realities of building management.