Fire Compartmentation of a Building

The design of a building and the number of fire compartment floors and walls are determined by several factors, these include:

  • The number of floors or storeys inc basements
  • The number of protected staircases
  • The buildings construction and age
  • The square meterage of each floor or storey
  • The travel distances
  • The type of occupancy i.e., residential care, office, factory, hospital
  • If the building has any fixed fire installations such as sprinklers
  • The max number of persons who may be in the building 

The above is not an exhaustive list, but cover the main considerations when identifying fire compartment walls and floors.

There are a range of fire resisting standards for compartment walls and floor which can be found in the latest

Building Regulations Code of Practice Part B

In addition, there are a range of guidance documents and British Standards (BSI) ,that determine the location and size of any fire compartment, when a building is being assessed by a 'competent' building surveyor.

A buildings fire compartments are usually between 30 minutes and 60 minutes fire protected but can be rated higher depending on size, risk and usage. 

When considering the location of these fire compartments, travel distances are considered in accordance with HM Government guidance documents on fire risk assessments. These travel distances are also determined by the type of occupancy, for example in residential nursing homes, it is considered that the occupancy is either 'independent', 'dependent', or 'highly dependent' on staff, due to their care needs and therefore fire compartments must be small enough for the number of staff on duty to be able to evacuate in a set time during any fire emergency. 

Generally, the higher the building the higher the risk to life should a fire occur. This is where multiple protected staircases are installed to ensure that evacuation can take place without hindering access of the fire and rescue service should they need to assist in any evacuation of a multi storey building, once any 'stay put' policy is no longer feasible.

In residential care, nursing care homes and hospitals the usual evacuation policy is one of 'phased horizontal evacuation' (PHE), this is where members of staff assist residents to evacuate horizontally into the next fire compartment, from where any fire breaks out. Each compartment is then evacuated until a protected staircase is reached. Depending on the severity of the fire the next phase would be for staff to assist residents down any protected staircase if they are above the ground floor.

All fire compartments must be both fire and smoke tight (Not dissimilar to the requirements of a submarines watertight compartments, but instead of water being the hazard it is fire and smoke and in particular smoke is the major issue that causes fatalities in a fire.

The more vulnerable the occupancy is, the higher the level of good sound fire and smoke compartmentation is required.

High rise buildings tend to have a fire strategy known as a 'stay put' policy, there has been some concerns in this area, particularly following the tragic Grenfell Tower fire in 2017 when 72 people lost their lives.

The issue with any 'stay put' policy is knowing how well the internal fire compartments will stand up to a fire, depending on the age of the building its construction and several other qualifying factors. The difficulty in confirming all of this without having an in-depth evasive survey being carried out, as alterations over the years may have compromised, certain fire compartments without this being known or understood by certain contractors and the 'responsible person'.

There is also another problem and that is the lack of good quality maintenance to the internal structure of the building. Items such as fire doors, lift shafts, services risers, can all affect the fire compartmentation, leading to a building being potentially unsafe for a 'stay put' policy. So not all buildings can maintain a 'stay put' policy until these issues have been identified and resolved. 

It is critical that a 'competent' person as referenced in the Regulatory Reform (fire safety) Order 2005 is employed to determine where fire compartmentation should be positioned. If the person is highly skilled, they will consider, not only building regulation standards, but the content of any fire risk assessment and fire strategy document, if one is available.

Once fire compartmentation is determined then generally a fire stopping survey is carried out to determine if there are breaches in the fire compartment walls and floors. This is a separate survey requirement.

Compartment surveys also cover any basement areas of a building and will also highlight any high-risk rooms that must be enclosed in their own fire compartment such as electrical switch gear rooms, boiler rooms and kitchens.

If required by our clients, building control, or the fire officer, plans can be marked with all the required fire compartment walls and floors, including high risk rooms, protected staircases and roof space compartments, particularly above any sleeping accommodation.

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