Fire compartmentalisation might not be as visible as smoke alarms or fire extinguishers, but it’s arguably one of the most critical fire safety measures in any building.
This passive fire protection strategy has saved countless lives across Hampshire and the UK by containing fires and protecting escape routes.
Let’s explore what fire compartmentalisation is, why it’s essential, and how it’s achieved in UK buildings.
What is Fire Compartmentalisation?
Fire compartmentalisation is the practice of dividing buildings into fire-resistant sections or compartments to prevent the spread of fire, smoke, and toxic gases. Volume 2 of Approved Document B defines a fire compartment as “A building or part of a building comprising one or more rooms, spaces or storeys constructed to prevent the spread of fire to or from another part of the same building or an adjoining building”.
Think of it as creating fireproof boxes within your building.
If a fire starts in one compartment, the fire-resistant barriers keep it contained, preventing it from spreading to other areas.
This buys precious time for occupants to evacuate and for the fire service to respond.
Why Fire Compartmentalisation is Critical for Safety
Fire compartmentalisation serves three vital purposes that make it indispensable for building safety in Hampshire and across the UK.
Life Safety: Protecting Escape Routes
The primary purpose of fire compartmentalisation is saving lives. By establishing isolated compartments, it curbs the spread of fire, smoke and harmful gases, offering crucial time for occupants to evacuate to designated safe zones. It plays a pivotal role in securing safe escape routes, giving people a fighting chance at survival.
Without proper compartmentalisation, fires can spread rapidly throughout a building, trapping occupants and blocking escape routes. Fire compartmentalisation prevents the immediate spread of fire which could trap the occupants of a building.
Property Protection
Beyond life safety, compartmentalisation protects valuable property and business assets.
When fire ignites, it can cause substantial damage to both structure and contents, costing on average £657,074 per incident.
By containing fires within smaller areas, compartmentalisation significantly reduces property damage and business disruption.
Firefighter Safety
Fire compartmentalisation also protects emergency responders by creating predictable fire behaviour and safer working conditions. It reduces the chance of fires growing and creating a danger to occupants, fire and rescue services, and people in the vicinity of the building.
Key Components of Fire Compartmentalisation
Effective fire compartmentalisation in Hampshire buildings relies on several interconnected elements working together as a complete system.
Fire-Resistant Walls and Floors
The foundation of any compartmentalisation strategy is fire-resistant construction. The spread of fire is prevented in compartmentalisation by using fire resistant walls, floors and other special measures that cope with openings in compartment lines.
The minimum period of fire resistance in compartment walls should be 30 minutes for single-storey buildings and 60 minutes for multi-storey buildings, although exceptions apply for buildings with sprinkler systems installed. These time periods are crucial – they represent how long the barrier can withstand fire conditions whilst maintaining its structural integrity.
Fire Doors: The Gatekeepers
Fire doors are perhaps the most visible element of compartmentalisation systems.
These aren’t ordinary doors – they’re specially engineered to resist fire and smoke penetration for specific time periods (typically 30 or 60 minutes). Fire doors play a critical role in containing the spread of fire and smoke, thereby protecting escape routes.
Every fire door must be self-closing and properly maintained to function effectively. A fire door left wedged open defeats the entire purpose of compartmentalisation.
Fire Stopping and Penetration Seals
One of the most critical but often overlooked aspects of compartmentalisation is fire stopping. Approved Document B 2019 Volume 1 ‘Dwellings’, Section 9 sets out the requirements for fire stopping and states that openings through a fire-resisting element for pipes, ducts, conduits or cable should be as few and small as possible and fire stopped.
Every time a pipe, cable, or duct passes through a fire-resistant wall or floor, it creates a potential weak point.
Services like pipework, electricity cables, and ventilation ducts are fundamental to the operations of all buildings – but they can also promote the spread of fire.
This is because to allow the services passage through walls, ceilings, and floors, a small gap or penetration will need to be created – breaching fire resistance.
Fire stopping uses specialised materials to seal these openings and restore the fire resistance of the barrier.
Penetration seals are passive fire protection systems used to maintain the fire resistance of a wall or floor that has cables or pipes passing through it.
Intumescent Materials
Many fire stopping products use intumescent technology – materials that expand when exposed to heat to create an insulating barrier.
Fire-rated sealants and foams: These materials expand under heat to seal gaps tightly and resist the spread of fire.
Intumescent strips: These materials swell when exposed to heat, effectively closing the joint as temperatures rise.
UK Building Regulations and Standards
Fire compartmentalisation in Hampshire buildings must comply with strict UK regulations and standards.
Approved Document B Requirements
Approved Document B (Fire Safety) is a critical part of the UK Building Regulations, focusing on reducing risks and ensuring safety in case of fire. This document provides statutory guidance on building regulations in England concerning fire safety within and around buildings.
The document is divided into two volumes: Volume 1 covering dwellings and Volume 2 addressing all other building types. Both provide detailed guidance on compartmentalisation requirements based on building use, height, and occupancy.
Testing and Certification Standards
All fire stopping products must undergo rigorous testing to British and European standards. Penetration Seals testing standards are set in BS EN 1366 Fire resistance Tests for Service Installations. The standard determines the method for ascertaining the fire resistance of horizontal and vertical ventilation ducts.
Professional Installation Requirements
The complexity of fire compartmentalisation means that installation should only be carried out by competent professionals. Approved Document B notes: “The use of certified installers will reduce the incidence of firestopping materials being installed by unskilled contractors and the use of unsuitable materials and reduce essential work and rework considerably”.
Compartmentalisation in Practice: Real-World Applications
Understanding how compartmentalisation works in different Hampshire building types helps illustrate its practical importance.
Residential Buildings
In blocks of flats, each unit typically forms its own fire compartment. Compartmentalisation can allow stay put policies to be implemented safely and effectively, for example in the instance a block of flats whereby each flat is its own compartment, this means that a full evacuation of the building is not always necessary as the fire is contained in that single compartment.
Healthcare Facilities
Hospitals and care homes use compartmentalisation to enable progressive horizontal evacuation. Similarly in a hospital where moving occupants vertically to different floors can prove challenging in an emergency situation, compartmentalisation means that residents can be moved horizontally to compartments on the same floor away from the fire.
Commercial Buildings
Office buildings and retail spaces use compartmentalisation to protect escape routes and limit business disruption. It can be used to protect areas that are of particular financial or strategic importance, such as IT suites or server rooms in the event of a fire breaking out.
Learning from History: UK Building Fires Where Poor Fire Compartmentalisation Led to Catastrophic Damage
Understanding the consequences of inadequate fire compartmentalisation becomes clearer when examining historic UK building fires. These cases demonstrate how poor fire containment can transform manageable incidents into national disasters.
The 2008 Royal Marsden Hospital Fire: A Modern Healthcare Fire Compartmentalisation Challenge
A more recent example demonstrates how even modern buildings can face compartmentalisation challenges. On 2 January 2008, a fire broke out in a plant room on the top floor of the hospital at the Royal Marsden Hospital in Chelsea, London. This world-renowned cancer treatment centre faced unique challenges that highlight the critical importance of effective compartmentalisation in healthcare settings.
The fire’s impact was severe: The entire roof of the Chelsea Wing of the hospital was burned through, and the top floor was also affected. What made this incident particularly concerning from a compartmentalisation perspective was the speed of smoke spread. The Intensive Care Unit (ICU) was one of the first areas to evacuate as smoke rapidly filled the area within 4-5 minutes of the fire starting.
The hospital’s fire response revealed both strengths and weaknesses in compartmentalisation planning. It had always been assumed that the building would be compartmentalised and a horizontal evacuation would suffice, according to the NHS London emergency preparedness review. However, the reality proved different – the hospital required complete evacuation of all 78 inpatients and approximately 120 outpatients, with evacuation completed in just 28 minutes.
The Royal Marsden case demonstrates several key compartmentalisation lessons. The full evacuation was completed in 28 minutes due to fantastic staff teamwork and leadership, but As with most hospitals, prior to the fire the RMH major incident plan did not incorporate the possibility of a complete site evacuation. This highlighted a critical gap in compartmentalisation planning – the assumption that passive fire protection would always contain fires sufficiently for horizontal evacuation only.
The 1992 Windsor Castle Fire: A Royal Lesson in Fire Spread
What started as a small incident quickly became a catastrophe due to structural vulnerabilities. The fire had spread rapidly due to the large cavities and voids in the roof. The false ceiling in St George’s Hall and the void for coal trucks beneath the floor had allowed the fire to spread. The lack of effective compartmentalisation meant that by 12:20pm, the fire had spread to St George’s Hall, a banqueting hall and the largest of the State Apartments.
The scale of the disaster was immense: 100 rooms were affected by the fire, with damage including the complete destruction of the Crimson Drawing Room and significant damage to multiple state apartments. The restoration cost £36.5 million (equivalent to £74 million today) and took five years to complete.
The 1698 Whitehall Palace Fire: When Europe’s Largest Palace Burned Down
An even more dramatic example of fire spread occurred in 1698 at Whitehall Palace. The Whitehall Palace fire started on the afternoon of 4 January 1698, when a Dutch maidservant was drying linen sheets on a charcoal brazier in a bed chamber at Whitehall Palace. However, the maid left the room. It only took a second for the sheets to ignite, then to set fire to the bed hangings, and then the whole lodging was ablaze.
The palace’s construction made fire spread almost inevitable. Whitehall Palace was still a largely timber structure, and flames travelled rapidly from building to building. Before long, flames were rising form the whole of the southern part of the palace. The fire’s devastating progression showed the consequences of poor compartmentalisation: the flames quickly spread throughout the palace complex, raging for 15 hours before firefighters could extinguish them.
The result was the complete destruction of what was then Europe’s largest palace complex. Over 150 houses had been burnt down, 20 houses had been blown up in an attempt to stop the fire. Only the Banqueting House survived, saved by Christopher Wren’s quick thinking in ordering it to be sealed against the flames.
The Glasgow School of Art Fires: Modern Fire Compartmentalisation Failures
More recently, the Glasgow School of Art experienced two devastating fires that highlighted ongoing compartmentalisation challenges in historic buildings. The 2014 and 2018 fires at the Mackintosh Building demonstrated how inadequate fire protection can destroy irreplaceable cultural heritage.
The delayed installation of a water mist suppression system and presence of obsolete ventilation ducts exacerbated two fires at the Glasgow School of Art, according to a Parliamentary report. The investigation found critical compartmentalisation failures: The legacy ventilation system was referenced in the 2014 fire report as a major contributor to rapid spread of fire. The report also found that ‘uncontrolled fire growth and rapid development’ of the fire – half of the building was ‘well alight’ within 38 minutes of the arrival of firefighters – had been fuelled by the unlimited air supply drawn through ‘exposed and unprotected’ ventilation ducts.
The restoration work between the two fires created additional vulnerabilities. To have provided effective compartmentation would have meant deconstructing the interior of the Mackintosh Building to find where voids existed. Only by stripping it back to its masonry structure could we have been certain of stopping all these voids and providing compartmentation, the Glasgow School of Art explained.
The result was complete destruction in the 2018 fire, with almost everything within the building severely damaged or consumed in the fire.
<iframe width="400" height="500" frameborder="0" src="https://www.bbc.co.uk/news/av-embeds/60112316/vpid/p0bk6ksn"></iframe>The 2017 Grenfell Tower Fire: The Ultimate Fire Compartmentalisation Failure
The most devastating example of fire compartmentalisation failure in modern UK history occurred on 14 June 2017 at Grenfell Tower in North Kensington, London. This tragedy, which claimed 72 lives, fundamentally changed how we understand fire compartmentalisation and its critical importance in high-rise buildings.
Grenfell Tower was designed around a fundamental fire compartmentalisation principle. Like many other tower blocks in the UK, Grenfell Tower was designed to be operated under a “stay put policy” in the event of fire. The idea was that if a fire broke out in one flat, thick walls and fire doors would contain the fire long enough for the fire service to bring it under control (compartmentation). Only those in the affected dwelling would be expected to evacuate.
However, the 2012-2016 refurbishment fundamentally compromised this compartmentalisation strategy. The external cladding made of aluminium composite material (ACM), installed when the 1970s tower block was refurbished between 2012 and 2016, caught light during a kitchen fire and rapidly spread. The cladding at Grenfell failed to meet the requirements of building regulations [at the time of the fire] – which say that external walls must adequately resist the spread of fire.
The compartmentalisation failure was rapid and catastrophic. Once the fire was in the external cladding at Grenfell compartmentation was breached. Prof Torero believes compartmentation was breached by 1:05 (11 minutes after the fire started at 00:54) as at that point you can see dripping PE so you know that external propagation is happening. At this point you know that the fire is progressing in an unexpected manner and there is a flame creeping into the external components of the building.
The external fire system created an entirely new fire spread mechanism that existing compartmentalisation could not contain. The polyethylene core in the ACM panels acted like “solid gasoline,” whilst the air gap behind the cladding functioned as a chimney, allowing flames to grow upwards inside it, inaccessible to firefighters’ hoses. This external fire then re-entered the building through windows, bypassing all internal compartmentalisation measures.
The Grenfell tragedy exposed fundamental flaws in compartmentalisation planning and building regulations. The inquiry concluded that “Following the refurbishment, the external walls of the building did not comply with the Building Regulations because they did not adequately resist the spread of fire over them. On the contrary, they promoted it.” This failure invalidated the entire fire safety strategy for the building, including the stay-put policy that residents and firefighters relied upon.
The aftermath of Grenfell has led to a complete re-evaluation of compartmentalisation requirements across the UK, particularly for high-rise buildings, highlighting how critical proper compartmentalisation design and maintenance truly is for building safety.
Common Themes in Compartmentalisation Failures
These historic fires reveal consistent patterns that emphasise the importance of proper compartmentalisation:
Hidden Voids and Cavities: Both Windsor Castle and Glasgow School of Art suffered from concealed spaces that allowed fire to spread undetected. Modern buildings must ensure all voids are properly fire-stopped.
Obsolete Building Systems: Old ventilation systems, particularly those not designed with fire safety in mind, can become highways for fire spread. Regular assessment and upgrading of building services is essential.
Construction Materials: The use of combustible materials in construction, as seen in the timber-heavy Whitehall Palace, can accelerate fire spread when compartmentalisation fails.
Maintenance and Restoration Challenges: Historic buildings often face compartmentalisation compromises during restoration work, as demonstrated at Glasgow School of Art.
These examples underscore why modern fire compartmentalisation requirements exist and why regular maintenance and professional assessment are crucial for building safety in Hampshire and across the UK.
Common Fire Compartmentalisation Failures in Modern Buildings
Despite its importance, compartmentalisation often fails due to poor maintenance or inadequate installation. Common issues include:
- Compromised penetration seals: Modifications to buildings often create new openings that aren’t properly fire stopped
- Damaged fire doors: Doors that don’t close properly or have damaged seals
- Inadequate maintenance: The penetration seals should be regularly inspected – ideally, using the ASFP document TGD 17 and the Building Engineering Services Association (BESA) online service SFG20
Maintaining Effective Fire Compartmentalisation
Regular inspection and maintenance are essential for compartmentalisation to remain effective. The fire compartmentalisation of your building should be reviewed as part of every fire risk assessment.
Building owners should ensure that:
- Fire doors are regularly inspected and maintained
- All penetration seals remain intact
- Any building modifications are properly fire stopped
- Staff understand the importance of keeping fire doors closed
The penetration seals should be regularly inspected – ideally, using the ASFP document TGD 17 and the Building Engineering Services Association (BESA) online service SFG20.
The Future of Fire Compartmentalisation
With increasing building heights and complexity, compartmentalisation continues to evolve. Recent updates to Approved Document B have introduced new requirements for high-rise residential buildings, including enhanced compartmentalisation standards and additional sprinkler requirements.
The Building Safety Act 2022 has also introduced new responsibilities for building owners to maintain comprehensive fire safety information throughout a building’s lifecycle, including detailed records of compartmentalisation systems.
Professional Fire Safety Support in Hampshire
Effective fire compartmentalisation requires expert knowledge and professional installation. For Hampshire property owners, ensuring your compartmentalisation systems meet current regulations and remain effective requires ongoing professional support.
ESI: Electrical Safety Inspections understands the critical relationship between electrical systems and fire safety. Many fires start from electrical faults, making it essential to ensure both your electrical installations and fire compartmentalisation work together effectively. Our team provides comprehensive electrical safety assessments alongside fire safety guidance for commercial properties, workplaces, and rental accommodation across Hampshire and Farnborough.
Whether you need electrical safety certificates, fire risk assessments, or advice on maintaining compartmentalisation systems, ESI combines electrical expertise with fire safety knowledge to keep your Hampshire property compliant and safe.
The wrap
Fire compartmentalisation may be invisible to most building occupants, but it’s one of the most important fire safety systems protecting lives and property across Hampshire. By understanding how compartmentalisation works and ensuring proper installation and maintenance, building owners can significantly improve safety outcomes and regulatory compliance.
Remember: effective fire compartmentalisation isn’t just about meeting building regulations – it’s about creating multiple layers of protection that give people the best possible chance of escaping safely in an emergency. In a county like Hampshire with diverse building types from historic properties to modern developments, proper compartmentalisation is essential for community safety.
Contact ESI: Electrical Safety Inspections today to ensure your Hampshire property combines effective fire compartmentalisation with safe electrical systems for comprehensive protection.
Further Reading and Resources:
- Gov.UK – Approved Document B: Fire Safety
- Ventro Group – Fire Compartmentalisation Guide
- Fire Seals Direct – What is Fire Compartmentalisation?
- BASSE Group – Fire Compartmentalisation Importance
- CPFP – Fire Penetration Sealing Systems
- Clearview Communications – Fire Stopping Regulations
- Building Engineer – Fire Stopping Responsibility
