Project Description
Application 3: Single Staircase Office
This animation shows a commercial office building that would normally have two separate staircases to be compliant with current guidance. In many cases this provision is commercially unviable. Using an alternative approach, it can be shown that a sprinkler system and one single staircase provides a safer solution. Whilst the animation focuses on a single staircase solution, similar approaches could be used to justify the removal of other measures in larger commercial buildings.
Guidance
All guidance requests that non-residential buildings have a minimum of two staircases when the top storey height exceeds 11m above ground. Two staircases can be difficult to include in commercial buildings when building plots are small or of an irregular shape. In these cases, an alternative solution to justify a single staircase provision needs to be found to increase net lettable area and make the project feasible.
Fire Suppression and Probability
Whilst there are many ways of justifying a single staircase solution for buildings that only marginally exceed the 11m criterion, the most robust way of doing this at heights approaching 30m is to use a sprinkler system and assess how safety levels compare to those when the building has two staircases only. We are able to demonstrate how much safer the alternative design is, using evacuation software and computational fluid dynamics that simulate the movement of smoke, its temperature and how visibility levels reduce over time. Using probabilistic methods we then consider sprinkler system and fire door reliabilities to determine which of the two solutions is more robust. In our experience the alternative approach always provides a safer building and the increased net to gross floor area pays for the sprinkler system and much more.
Fire Safety Measures
When we adopt this solution we tend to recommend automatic fire detection and alarm systems, compliant travel distances, no more than 60 persons occupying a single floor level and fire compartmentation between floors. However, each project is unique with alternative approaches tending to be tailored according to the risks we identify as part of the design process.
Façade Fire Resistance
Many of these buildings tend to be erected on heavily constrained sites within close proximity of neighbouring buildings. This is one area where the benefits of introducing a sprinkler system become even more apparent. Using alternative approaches it is sometimes possible to remove fire resistance from certain elements i.e. external façades. In the cases of fully glazed envelopes this can generate considerable cost savings to projects.
We have a strong track record for having removed fire resistance from façades in all types of buildings using a variety of approaches.
Guidance
All guidance requests that non-residential buildings have a minimum of two staircases when the top storey height exceeds 11m above ground. Two staircases can be difficult to include in commercial buildings when building plots are small or of an irregular shape. In these cases, an alternative solution to justify a single staircase provision needs to be found to increase net lettable area and make the project feasible.
Fire Suppression and Probability
Whilst there are many ways of justifying a single staircase solution for buildings that only marginally exceed the 11m criterion, the most robust way of doing this at heights approaching 30m is to use a sprinkler system and assess how safety levels compare to those when the building has two staircases only. We are able to demonstrate how much safer the alternative design is, using evacuation software and computational fluid dynamics that simulate the movement of smoke, its temperature and how visibility levels reduce over time. Using probabilistic methods we then consider sprinkler system and fire door reliabilities to determine which of the two solutions is more robust. In our experience the alternative approach always provides a safer building and the increased net to gross floor area pays for the sprinkler system and much more.
Fire Safety Measures
When we adopt this solution we tend to recommend automatic fire detection and alarm systems, compliant travel distances, no more than 60 persons occupying a single floor level and fire compartmentation between floors. However, each project is unique with alternative approaches tending to be tailored according to the risks we identify as part of the design process.
Façade Fire Resistance
Many of these buildings tend to be erected on heavily constrained sites within close proximity of neighbouring buildings. This is one area where the benefits of introducing a sprinkler system become even more apparent. Using alternative approaches it is sometimes possible to remove fire resistance from certain elements i.e. external façades. In the cases of fully glazed envelopes this can generate considerable cost savings to projects.
We have a strong track record for having removed fire resistance from façades in all types of buildings using a variety of approaches.
Semper Approach
This is one of the best examples of how fire safety engineering can be used to increase safety levels, whilst permitting greater flexibility at a much lower cost.