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Building services supports are commonly used for supporting life safety systems that are required to function for specified times in the event of fire to facilitate safe evacuation and firefighting operations. In these applications it is critical that the supports remain structurally sound and maintain their supporting function for the same duration as the life safety system.
No, all the life-safety systems standards have this requirement although it is only recently that it has started to come under scrutiny. Like many areas of construction, this is another outcome of the Building Safety Act driving compliance and the need for robust evidence especially for anything of such safety critical nature.
Steel loses its strength rapidly when exposed to fire - just 4% of its original strength after 90 minutes fire duration. Channel support systems can experience large deformations and buckling due to their thin-walled and open-sided profiles. For this reason, standards such as BS 8519 require brackets to be adequately sized to account for the significant loss of strength.
The right way round - "Design the support to suit the conditions. Don't attempt to fit the conditions to the support".
In short, one which can be shown to carry the applied loads for the required fire duration without losing structural stability. Once a support fails structurally the services experience excessive movement if not outright collapse.
To prove supports are safe is a design consideration based on the following factors:
From this information a support can be designed with the appropriate strength providing the fire performance for each element of the support is known and has robust evidence behind it.
The shortcut and the risk
A fire label on a datasheet feels like a result. But the datasheet belongs to a product, not necessarily the arrangement you are about to install. Change the load, the span, the substrate or introduce other components and it may no longer cover what hangs from the ceiling.
Drop the datasheet in the file and move on. It is fast, it looks like an answer, and it ticks the box on the day.
The risk turns up later, when a reviewer questions whether that data really applies to this support, this load and this substrate. Often, it does not.
Define the specific load, bracket geometry, substrate and fire duration and identify a support arrangement that comes with the appropriate evidence.
Keep the reasoning, so the decision can be explained at review and handover, not just made under pressure on site.
For practical context, read the fire tested versus fire rated supports guide. The separate Fire Resistant 18th Edition cable fixing range lists cable fixing products. Choosing a catalogue item does not by itself evidence the complete installed support arrangement.
Sound familiar?
The fire support requirement appears after routing, coordination and procurement are largely fixed. Even worse when the supports are already installed. Now every option costs more and moves the programme.
A fire-tested datasheet gets treated as the answer. Then a technical reviewer asks whether it covers the actual arrangement, and the conversation goes quiet.
Site experience and a quick reassurance carry the job forward, until someone has to show why the support holds up in fire, and the reasoning was never written down and the critical evidence is missing.
Before the design is locked in
Answer these early and the fire support requirement stays a design decision. Leave them, and it becomes a late-stage scramble over cost, programme and who is responsible. This is the simplest place for MIDFIX to help.
Identify which services require fire resistant supports. This broadly applies to all life safety systems and other services where they are not independently supported. Supports at service penetrations will also require fire resistance comparable to the fire stopping.
Does the available space allow the critical services to be supported independently of general services? This often determines the sizing, type and ultimately the cost of the supports.
Are there specific fire conditions that need considering and what fire duration are the systems and supports required to function for?
Are there any project specific requirements for fire resistant supports? Typically project specifications just refer to the relevant installation standards but it's worth checking there is nothing more.
We carry design responsibility for the support arrangement and hold professional indemnity insurance. Agree any project-specific design cost before tender.
Three solutions
Part of the job is knowing what is possible before anyone promises a result. Channel systems have a relatively small load bearing capacity in fire conditions and are generally limited to trapeze brackets by the available test evidence. For higher loads, frames and service modules other solutions are required.
Typically for trapeze type brackets where the bracket arrangement sits inside the scope of the testing and the project conditions genuinely match that scope.
Based on traditional steel profiles and assessed for fire under the recognised structural steel design codes. For higher loads and larger spans than possible with channel or modular steel and suited to support frames and service modules.
A hybrid support combines channel with traditional steel. This gives higher load bearing capacity than is possible with channel alone while still having the versatility of channel for easily connecting services to the support.
Evidencing that supports are suitable for life safety applications is crucial information. Assumptions, extrapolations and 'rules of thumb' are not evidence. Long standing reliance on reduction factors for channel are shown to be widely inaccurate.
EAD 280016 is the harmonised technical specification and gold standard for testing and assessing channel and modular steel supports for fire conditions. The EAD framework establishes common rules for fire assessment ruling out individual manufacturer interpretation. Channel supports based on EAD verified data have the strongest evidence basis available.
Custom steel supports are assessed and verified for fire performance based on the structural steel fire design code EN 1993-1-2. The broad scope of the design code facilitates fire assessments for multiple configurations of supports. Eurocode-based structural engineering reports provide robust evidence for heavy duty supports, frames and modules.
What to send
No model yet? A sketch and a phone call are enough to get started.
What you get back
We provide the physical supports designed to meet the project's fire requirement, together with a fire engineering report that sets out the evidence for the support arrangement. The report explains the basis for the design and the assumptions and limits that apply.
The questions people actually ask
We would not put a blanket "fire rated" label on any support, ours included. What matters is whether the arrangement you are installing can be shown to carry its load for the fire duration the project needs. Tell us the load, layout, bracket type and substrate, and we will set out what can be evidenced for that application, and where the limits are.
Start with what the supports carry. Standards for life safety systems, such as BS 5839-1 for fire alarms, BS 5266-1 for emergency lighting and BS 8519 for life safety power and control cables, include guidance on how those cables are supported in a fire. Supports either side of a penetration seal need checking too, as do services that share supports with life safety systems or run above them. Then check the project specification and ask the fire engineer, because the project can ask for more than the standards do.
BS EN 12845, the sprinkler standard, does not ask for them. It sets pipe support spacings and loads for normal conditions, with an allowance for the heat early in a fire, because sprinklers are expected to operate in the first few minutes. The project specification or fire engineer may still ask for more. And if sprinkler pipes run above a life safety route, their supports can affect the ones underneath.
Not on its own. A fire test covers what was tested: that load, span, bracket type and duration, and it is not technically possible to extrapolate wider results from it. Your support also has rod, connections, anchors and a substrate, and your project has its own loads. Our MX channel route is EAD-tested, so we can assess MX arrangements that sit within the tested scope. Outside that scope, or for heavier loads, we look at another route, such as custom steel designed to EN 1993-1-2.
You receive a fire engineering report that sets out the evidence for the support arrangement, along with the physical supports designed to meet the project's fire requirement.
The fire requirement and where it came from, the fire duration, drawings, sketches or photos of the supports, the loads, spans and geometry, the substrate it fixes to, and any test data or calculations you already have. Tell us whether you are planning ahead or dealing with something already on site. No model yet? A sketch and a phone call are enough to start.
Get MIDFIX involved early
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