Ensuring that your building has effective fire compartmentation is an important part of any passive fire protection strategy.
It should be incorporated during a construction project as early as possible, so that a building remains structurally sound in the event of a fire. Integrating it early with active systems, like automatic fire sprinklers, creates a holistic safety strategy that can reduce construction costs and design limitations.
Read on as we introduce you to fire compartmentation and key considerations to establish fire safety best practices. The team here at Hydro Protect is the UK’s leading fire sprinkler specialists, and we’re experienced in the design, installation and maintenance of fire sprinklers in London. We’ve worked on a variety of projects and can advise on the best fire safety methods to remain compliant with the latest Fire Safety Regulations.
A Summary Of Fire Compartmentation
| Core Topic | Key Concept (Passive Fire Protection) | The Fire Sprinkler Advantage (Active Fire Protection) |
| What Is It | Dividing a building into fire-resistant “cells” (using walls, floors, and fire doors) to contain fire and smoke at its origin for a specified time (e.g., 30, 60, or 120 mins). | Automatically responds to and suppresses a fire at its source, drastically reducing the thermal stress and heat placed on those passive barriers. |
| Where It’s Found | Walls, ceilings, fire doors, cavity barriers in hidden voids, and HVAC ductwork (fitted with fire dampers and intumescent fire-stopping). | Strategically piped throughout the entire building layout, providing 24/7 active coverage where manual firefighting or passive walls cannot reach. |
| UK Regulations | Mandated by Approved Document B – currently the 2019 edition incorporating the 2020, 2022, and 2025 amendments – and enforced by the Regulatory Reform (Fire Safety) Order 2005, as updated by the Fire Safety Act 2021. Strict rules apply to high-risk structures and buildings over 11m. Further amendments take effect in September 2026 (staircases and evacuation lifts in higher-risk residential buildings) and September 2029 (fire resistance classifications). The Building Safety Regulator (BSR) now keeps Approved Document B under continuous review. | BS 9999 and BS 9991 allow for major regulatory “trade-offs” if sprinklers are installed, unlocking architectural and cost benefits. |
| Key Commercial Benefits | Protects escape routes, ensures safe occupant evacuation, and limits structural property damage. | Design Freedom: Allows for larger compartment sizes, longer escape travel distances, reduced fire resistance periods for walls, and open-plan layouts. |
| Action Plan for Failures | If a survey (Type 2/4 FRA) reveals compartmentation breaches, they must be legally remediated as a matter of priority under the Building Safety Act. | Where historic structural fixes are too disruptive or costly, installing a sprinkler system can often act as an approved compensatory measure to achieve compliance. |
What Is Compartmentation In Fire Safety?
As a part of Approved Document B, Volume 2, Fire Compartmentation is defined 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’.
It is a strategy that divides buildings into smaller, fire-resistant cells using walls, floors and doors to restrict fire and smoke to the point of origin for a specified period. In turn, this protects escape routes, allows for safe evacuation and limits property damage.
Where Are Fire Compartmentation Systems Found?
Walls & Ceilings
Each wall and ceiling that defines a compartment must be reinforced with fire-resistant materials. This could be in the form of cavity barriers in voids between walls and floors, designed to resist fire for a specified duration. For example, these could be placed between different flats, adjoining terraced houses, or commercial or mixed-use units.
HVAC Systems
HVAC systems are connected throughout a building, which means that they can enable the spread of fire if not adequately protected. HVAC systems must be fitted with fire dampers that immediately close when exposed to heat, and appropriate fire-stopping solutions must be applied to pipes and ducts.
Fire Doors
Specialised doors in corridors, stairwells, and at compartment boundaries. They prevent the spread of fire while allowing safe evacuation.
When Is Compartmentation Required?
Fire compartmentation is required wherever there is a need to prevent the rapid spread of fire and smoke.
It is mandatory to subdivide escape routes, such as stairwells, separate different occupancies, protect high-risk plant rooms, and, in multi-occupied residential buildings, especially flats over 11m in height. UK regulations also state that flats over 11m in height must have automatic fire suppression systems. These systems are mandatory in new-build residential blocks. As of March 2025, automatic sprinkler systems are also mandatory in all new-build care homes, irrespective of height, reflecting the higher risk profile of these buildings. Care home compartments are additionally required to be limited to 10 beds, with self-closing fire doors throughout.
Fire compartmentation is primarily mandated by Approved Document B (Fire Safety) of the Building Regulations in England – currently the 2019 edition incorporating the 2020, 2022, and 2025 amendments. The legal obligation to maintain and inspect these compartments is outlined in the Regulatory Reform (Fire Safety) Order 2005, as subsequently updated by the Fire Safety Act 2021. Note that Approved Document B applies to buildings in England only; separate region-specific guidance applies in Wales, Scotland, and Northern Ireland.
Why Is Compartmentation Important?
Fire compartmentation slows the spread of fire and toxic smoke, allowing occupants to evacuate and providing a safer environment for firefighters.
It keeps the designated escape routes clear of smoke and fire, whilst creating a more manageable environment for Fire Fighters.
Maintaining effective compartmentation is a key legislative requirement for property management and is sometimes a mandatory condition for building insurance to be valid.
How Fire Sprinklers Work Hand-in-Hand With Fire Compartmentation
Fire sprinkler systems significantly enhance fire compartmentation by controlling a fire at its source. This prevents it from breaching the physical barriers set out by the compartmentation. Rather than replacing the passive fire walls, a fire sprinkler system will act as an extension of your existing fire compartmentation, containing fires within the room of origin. This allows for greater flexibility in building designs.
Often, when fire sprinklers are installed in a property, as the risk of unchecked fire spread is reduced, building regulations allow designers to increase compartment sizes and use open-plan layouts, particularly in loft conversions, as the structural fire-resistance requirements are reduced.
Fire safety is divided into two categories, active and passive systems. The two work together, and if you are installing or already have a fire compartmentation system, the active suppression of fire sprinklers will buy even more time for evacuation, protecting the passive structural aspect of your building.
How To Achieve Fire Compartmentation
Fire compartmentation is achieved by dividing a building into compartments, or cells, using fire-resistant materials. Overall, the goal is to contain the fire at its point of origin, so this includes constructing floors and walls using materials such as specific concrete, masonry, and specialist fire-rated plasterboard. These materials can withstand fire for a designated period, such as 30, 60 or 120 minutes.
Where doors and windows create openings in your fire compartmentation, ensure that these openings don’t affect your fire safety. Any doorways must be fitted with certified fire doors equipped with self-closing mechanisms. Fire-resistant glass must be used in windows so the integrity of the wall is not compromised.
Services such as pipes, cables and ventilation ducts that pass through walls and floors also require attention. These can breach a fire compartment, leaving a gap, and therefore, firestopping is required. Firestopping involves using specialised intumescent sealants, pillows, mortars, or wraps that expand when exposed to heat, therefore tightly sealing the gaps around the utilities.
Ventilation ducts are another way that fire and smoke can travel through compartments. They, therefore, need fire dampers installed throughout the ductwork where it crosses the compartment. This way, in the event of a fire, the dampers will automatically close, blocking the path of the fire and smoke.
Fire can also spread through hidden voids, including the spaces above suspended ceilings, inside hollow walls, or beneath raised flooring. In these circumstances, cavity barriers are needed.
What Are The Fire Compartmentation Requirements?
In England, fire compartmentation requirements are stated in Part B of the Building Regulations (Internal Fire Spread — Structure), with technical guidance set out in Approved Document B. The current edition is the 2019 version, incorporating the 2020, 2022, and 2025 amendments. Core requirements include general maximum compartment size limits, mandatory specific compartments, minimum periods of fire resistance, special rules for high-risk and tall buildings, and strict penetration and cavity controls.
It is important to note that Approved Document B is now subject to a phased programme of further updates:
- March 2025 (now in force): New obligations on fire safety information at building completion (Regulation 38), mandatory sprinklers in all new care homes, and the removal of national fire reaction-to-fire classifications (BS 476 references for reaction to fire and roofs).
- September 2026: Requirements for multiple common staircases in residential blocks of 18m or taller, and new design provisions to support evacuation lifts in blocks of flats.
- September 2029: Full removal of remaining BS 476 references in relation to fire resistance, completing the transition to current European-aligned test standards.
The Building Safety Regulator (BSR) has been instructed to keep Approved Document B under continuous review, and a further public consultation on additional technical changes was launched in March 2026. Building owners, developers, and designers should ensure they are working to the correct version of the guidance for their project’s application date, given the transitional provisions that apply to each amendment.
How Fire Sprinklers Can Save Fire Compartmentation Costs
By installing automatic fire sprinkler systems, architects and developers can achieve compliance while finding significant design freedoms.
Often, permitted floor areas of compartments can be increased in commercial buildings if sprinklers are present.
Structural fire rating requirements for walls and floors can frequently be reduced, sometimes from 60 minutes down to 30 minutes, which can potentially save thousands of pounds in materials.
In the presence of fire sprinklers, escape routes can be longer, allowing for more open-plan layouts and better space utilisation.
Plus, in certain layouts, the required rating of fire doors protecting your escape routes can be lowered if the space has an adequate fire sprinkler system.
What Should I Do If My Building Does Not Have Adequate Fire Compartmentation?
If you suspect that your building has inadequate fire compartmentation, the situation must be addressed as a priority. In the UK, failing to maintain compartmentation is a serious breach of the Regulatory Reform (Fire Safety) Order 2005 and the Building Safety Act.
As a building owner, landlord, or responsible person, you have a legal responsibility to ensure these life safety measures are in place and that the property is compliant. This includes a linked, working fire alarm system so everyone is warned quickly and efficiently if a fire starts. A third-party accredited fire safety professional should conduct a Type 2 or Type 4 Fire Risk Assessment, or a dedicated Compartmentation Survey. This will provide you with a detailed list of required work.
Active Suppression and Passive Containment
Passive compartmentation systems essentially act as a shield. They will hold back a fire, but will not put it out. Eventually, severe fires can get through passive barriers.
Fire sprinklers will deal with the fire, suppressing the heat output, and by keeping the heat low, sprinklers ensure that walls, fire doors, and fire-stopping materials are put under minimal stress. This helps them to hold up for their intended duration, allowing firefighters to attend the scene and deal with the situation, minimising overall damage.
Ensure That Your Building Is Compliant Today
Effective fire safety isn’t a choice between active suppressive and passive containment. Choosing the right balance of the two is what will keep your property safe, minimising damage in the event of an emergency.
While fire compartmentation will provide you with the structural side of your building’s defence system, having an expertly designed fire sprinkler system is what provides the immediate, life-saving response that keeps this defence system resilient.
At Hydro Protect, we specialise in bridging this gap, and by involving our team early in your design or remediation process, we can help you ensure complete compliance with UK building regulations to safely reduce structural costs and ensure that your property is protected.