The choice between stay put and simultaneous evacuation has profound implications for a building's fire strategy.
25 February 20254 min readFire Safety Services
Two Fundamentally Different Evacuation Strategies
Stay put and simultaneous evacuation are the two principal evacuation strategies for multi-occupied residential buildings in the UK. The choice between them has profound implications for building design, fire safety management, and the safety of occupants. Understanding the difference — and knowing which strategy applies to your building — is essential for anyone involved in fire safety for residential developments.
What Is Stay Put?
Stay put, also known as defend in place, is an evacuation strategy in which occupants who are not directly affected by a fire remain in their flats rather than evacuating. The strategy relies on the principle that a well-designed and properly maintained fire compartmentation system will contain a fire within the flat of origin for long enough for the fire and rescue service to arrive and extinguish it.
Under a stay-put strategy, only occupants in the flat where the fire has started — or those directly threatened — are expected to evacuate immediately. Other residents remain in their flats with doors and windows closed, reducing the risk of encountering smoke on stairwells and preventing the congestion that could impede firefighter access.
Stay put has been the standard approach for purpose-built blocks of flats in the UK for decades and is embedded in the design guidance in BS 9991 and Approved Document B. It works well where compartmentation is sound, fire doors are maintained, and the building has been designed and built correctly.
Stay put relies entirely on compartmentation integrity. If fire doors are propped open, compartment walls have unsealed service penetrations, or external cladding allows fire spread up the building facade, stay put cannot function as intended.
What Is Simultaneous Evacuation?
Simultaneous evacuation — also called full evacuation — is an evacuation strategy in which all occupants of a building evacuate at the same time when the fire alarm sounds. It is the standard approach for most non-residential buildings and for residential buildings where compartmentation cannot be relied upon to contain a fire.
Simultaneous evacuation requires a different building design from stay put. It demands that escape routes can accommodate all occupants evacuating at once — which typically means wider staircases, more escape routes, and a greater number of final exits. It also requires a building-wide fire detection and alarm system that can alert all occupants simultaneously.
When Is Each Strategy Appropriate?
The appropriate strategy depends on several factors:
Stay put is appropriate where the building has been designed and constructed with robust fire compartmentation, self-closing fire doors in good condition throughout, no combustible external wall systems that could allow external fire spread, and the fire and rescue service can access the building and any affected floor within an acceptable response time
Simultaneous evacuation may be required where compartmentation is inadequate or cannot be verified, where external wall fire risk has been assessed as high or very high under PAS 9980, where the building has a waking watch due to identified fire safety deficiencies, or where a fire risk assessment has concluded that stay put is not appropriate for the building in its current state
The Grenfell Tower Fire and Its Impact on Evacuation Policy
The Grenfell Tower fire of June 2017 exposed the vulnerability of stay-put strategies where compartmentation fails and external fire spread is possible. Grenfell Tower operated a stay-put policy, and the rapid external spread of fire via the ACM cladding system meant that occupants on upper floors were not alerted in time to evacuate.
Following Grenfell, NFCC guidance was updated to allow fire and rescue services to override stay-put advice and call for simultaneous evacuation where they judge it necessary on arrival. The Building Safety Act 2022 and associated guidance has further strengthened requirements around evacuation planning for higher-risk buildings.
Changing from Stay Put to Simultaneous Evacuation
Where a fire risk assessment or fire safety review concludes that a stay-put strategy is no longer appropriate for a building, transitioning to simultaneous evacuation requires careful planning. The building's alarm system must be capable of alerting all occupants simultaneously, evacuation routes must be assessed for adequacy, residents must be informed and trained, and the fire and rescue service must be notified of the change in strategy.
Frequently Asked Questions
How do I know which evacuation strategy applies to my building?
The evacuation strategy for your building should be set out in the fire strategy report and reflected in the fire risk assessment. Residents can request this information from their freeholder or managing agent. For higher-risk buildings, accountable persons must make evacuation information available to residents.
Can a building change from stay put to simultaneous evacuation?
Yes. Where a fire risk assessment concludes that compartmentation is inadequate or external wall fire risk is high, the fire strategy may be changed to simultaneous evacuation as an interim measure while remediation is carried out. This requires changes to the alarm system and resident communication.
What is a waking watch?
A waking watch is a temporary measure used where a building's fire safety is deficient and a suitable alarm system is not in place. Trained staff patrol the building continuously to alert residents in the event of fire. It is an expensive interim measure that should be replaced with a common fire alarm system as quickly as possible.
Does a stay-put building need a fire alarm system?
Under a stay-put strategy, individual flats have their own smoke detection but there is typically no building-wide alarm — the common parts have a common fire detection system but it is not designed to alert all residents simultaneously. Where simultaneous evacuation is adopted, a building-wide alarm capable of alerting all occupants is required.
Who decides if stay put is appropriate for my building?
The responsible person — typically the freeholder or managing agent — is responsible for ensuring the fire risk assessment is suitable and sufficient. For higher-risk buildings, the Building Safety Regulator will scrutinise the evacuation strategy as part of the building safety case.
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