Open plan commercial spaces are increasingly common; however, these spaces can often directly contravene building regulations. It is important to understand all the applicable guidance and legislation and how a fire-engineered approach can overcome such issues.
For decades, creating large, open spaces within buildings has been growing in popularity. For some applications, the intended use will require a sizable, barrier-free area, and for others, it is used to create flexible, multifunctional spaces. More open layouts have also become a common way of introducing more natural light into a building, with significant energy saving and occupant well-being advantages that this provides.
Advances in build techniques have made this much easier to achieve but the building must still comply with the relevant building regulations to ensure it is safe for occupants.
The fire safety concern with large open-plan areas within buildings is that in the event of a fire, fire and smoke can spread more quickly than in a smaller compartment where it can be contained. The same applies to atria or open spaces between floors where a fire on a single floor can cause fire and smoke to spread up the building.
Building Regulation
Approved Document B (ADB) of the Building Regulations is the main source of direction on fire safety for new builds and refurbishments of both residential and non-residential buildings. The guidance provided by ADB aims to minimise the risk posed by fire and smoke and ensure the safe evacuation of occupants. However, the guidelines on elements such as travel distances, escape routes and room sizes are based on the assumption that a set of standard solutions will be used. For this reason, a strict application of ADB, or what is referred to as a code-compliant approach, may restrict the creation of open-plan spaces.
The alternative to a completely code-compliant solution is to apply a degree of fire engineering. This requires specialist fire engineers to look at the proposed plans for the building to identify where adjustments to the standard strategy can be made to create a tailored plan. The benefit of this is far greater design flexibility and the opportunity to create an internal layout that fits with the architect’s vision and meets the requirements of the end users.
For example, the standard approach to building design under ADB is to create compartmentation within the building to prevent the spread of fire and smoke. However, where a large space is desired, a fire-engineered approach may be to use fire suppression systems (sprinklers) as a solution to preventing the spread of the fire and making the open area safe. Other guidance documents may also be required, such as BS 9999. Early detection of a fire is also crucial to minimise the risk to occupants, so a more advanced, aspirating smoke detection system may be specified to achieve this.
CFD modelling
In general, the most important consideration when moving away from code compliant solutions is to demonstrate the safety of occupants has been maintained or even improved. Further justification in the form of Computational Fluid Dynamics (CFD) modelling may be required. CFD modelling uses computer analysis to show how fluid or air moves over a surface or within a space. When applied to fire design, the software uses a detailed virtual representation of the building created from the plans to simulate and map the spread of fire and smoke. It shows how the proposed layout and features of the building will affect the spread of the smoke and also highlights any areas of concern, such as where fire may spread more quickly or areas where smoke is hotter or denser.
Approved Document B guides on achieving the required level of fire safety; however, the approaches and solutions outlined in the regulations are not the only way to ensure occupant safety. By employing elements of fire engineering to adapt the standard method allows more flexibility in the creation of spaces that provide benefits to building users.
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