Fire Strategies – Code Compliant vs. Engineered Solutions

From a fire safety perspective One of the first fire decisions that must be made for all projects, is whether or not to implement a ‘code-compliant’ or ‘fire engineered’ approach in the creation of a fire strategy. Whether it is a retail unit, commercial office, factory or residential apartment block – this decision is vital.

Either approach to fire safety carries certain advantages as well as considerations which must be made. Whichever fire safety approach you choose to make, that decision should be made at the earliest stages of the project, where possible. Elements such as room sizes (or compartment), the number of staircases in a building and the corridor widths/lengths are all fundamental parts of the fire safety strategy.

In this latest edition of The FDS Blog we are going to be looking at the key differences between both the code compliant and engineered fire safety strategies. This includes both the benefits and possible pitfalls of each.

Approved Document B

Code Compliant Fire Safety Strategies

The code compliant fire safety option is seen as the ‘standard’ method of creating a fire safety strategy for your project. A code compliant approach remains close to the requirements structured in Approved Document B (ADB) of the Building Regulations and other British Standards.

This prescriptive method, working to the letter of these regulations, can ensure a simplified method of fire safety strategy. This makes the selection and specification of your project’s fire safety systems straightforward and easy to implement.

Code compliant fire strategies are more quickly approved by Building Control due to working within the dictated guidelines.

planning

Naturally, the prescriptive nature of a code compliant approach means that there are a limited choice of fire safety and smoke ventilation systems that it recommends for use.

The ABD largely requires the use of Natural Smoke Ventilation systems which make use of a 1.5m2 external window, or where this isn’t available a natural smoke shaft of 1.5m2/3m2. The performance of these natural smoke ventilation systems relies heavily on the use of the wind and the property of hot air rising and drawing in colder, denser air, to remove smoke.

A low-cost option but it does significantly reduce the amount of saleable space within a property due to the amount of space required by large smoke shafts. Despite this Building Regulations still calls for buildings using natural smoke ventilation systems to feature multiple staircases if they are over 11m in height, reducing the saleable space even further.

Another option available is the installation of pressurisation systems to create high-pressure areas, in locations such as staircases, to prevent the ingress of smoke and provide means of escape.

The addition of this pressurisation system allows buildings to have a single staircase even if over 11m in height. These pressurisation systems have set requirements outlined in BS EN 12101 Part 6, and their use can be easily justified by submitting calculations which show their effectiveness without the need for CFD analysis.  Pressurisation systems like these can also have relatively high costs as they require a pressurisation shaft with AOV windows from all floors, making them complicated to both install and commission.

Code compliant fire strategies are also very restrictive for developers, offering little flexibility in the creation of larger or open-plan spaces which are in high demand from end clients.

Engineered Fire Safety Strategies

Engineered fire safety strategies require specialist fire engineers to look closely at the proposed plans for the building in question. They will then identify the most appropriate fire strategy based on the building’s individual characteristics. This effectively creates a tailored plan specifically for your building.

This approach to fire safety strategy offers far greater flexibility as it is based on each individual building. In using various, more advanced, fire safety systems than outlined for use in code compliant fire safety strategies, further benefits can be added beyond simply increasing fire safety. Examples of these are the creation of larger open-planned spaces, extended travel distances and reduced costs.

It is worth remembering that the Approved Documents are intended to provide guidance for fire safety strategies, not just strict rules. Therefore, it is possible to justify changes to fire safety strategies with an engineered strategy by simply stating that requirements are met and the method by which they are met is unimportant, according to the ADB.

msvs

One of the basic ways in which the benefits of Engineered fire safety strategies can be brought to a development is via the use of solutions such as mechanical smoke ventilation systems.

Mechanical smoke ventilation systems consist of powered fans which are attached to a mechanical shaft. These systems allow for smoke to be extracted from the affected floor in the event of a fire – providing a safe escape route for its occupants.

These mechanical smoke ventilation systems are much more efficient when compared with natural systems, providing a greater level of smoke ventilation whilst using smaller smoke shafts. Mechanical smoke ventilation systems combined with intelligently designed fire strategies can also allow for the creation of larger sized rooms/compartments. A further benefit of mechanical systems are that travel distances can be extended and in certain cases entire staircases can be removed, which can provide both space savings and significant cost savings for developers.

As expected, there can be large variations between engineered solutions for each project. This means that all proposals must be submitted with evidence as to their effectiveness to Building Control for approval. This slightly more complex approval process when compared with code compliant strategies can result in more time required for the strategy to be approved.

Overview of Code Compliant and Engineered Fire Strategies

As shown in this blog post, there are many benefits and disadvantages to each of these fire strategies. Check out the pros and cons summary below to help you choose the best fire safety strategy for your project.

Code Compliant Fire Strategies

Pros of Code Compliant Strategies

  • Low system costs
  • Straightforward to implement
  • Quickly approved by building regulations

Cons of Code Compliant Strategies

  • Reduced room/compartment sizes
  • May require additional staircases
  • Loss of saleable space due to larger smoke shafts required
  • It is a ‘one size fits all’ approach

Engineered Fire Strategies

Pros of Engineered Strategies

  • Increased design flexibility
  • Extension of travel distances
  • Increased in compartment/room sizes possible
  • Approach prevents over specification
  • More saleable space possible

Cons of Engineered Strategies

  • Slightly longer approval process
  • Requires qualified fire engineers to be involved in the project from the start

More information on fire safety strategies can be found on our website – www.FDSConsult.com.

Contact our team of fire engineers today by phoning 01322 387 411, or email info@fdsconsult.com, to discuss your project further.

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