Knowing the basics of passive fire-stopping may sound easy; but it can be a complex topic that demands careful consideration and effective on-site communication.
Passive fire protection, to use the proper term, is one of the most important aspects of any building services installation, whether it involves components such as cables or cable trays or potentially sizeable elements such as pipes and ductwork. A building with incorrect fire-stopping can be as dangerous as a building with none at all.
It is worth noting here that passive fire protection is not an alternate to other methods of protection against the harmful effects of fire, but an addition to. Regulation 521.10.202 of BS 7671 will still require cables to be supported against premature collapse, for example, regardless of what passive fire protection measures are in place.
Passive fire-stopping is after all an essential requirement of BS 7671: 2018 Wiring Regulations. It can also be integral to compliance with UK legislation such as the Health and Safety at Work etc. Act 1974, the Electricity at Work Regulations 1989, and Construction (Design and Management) Regulations 2015.
Despite this provision, many electrical contractors fall short in this aspect of electrical installation and design.
Electrical installation in buildings tends to involve locating, sharing and, in many cases, making or enlarging holes in walls or other partitions.
But these partitions are there for a reason, one of which is likely to be to stop the spread of fire and smoke. Whenever building services work penetrates walls, floors or ceilings, it is therefore vital to maintain and, if need be, reinstate the integrity and fire rating of the construction.
This requirement also applies to cable containment systems such as trunking. Where the containment passes through a barrier, the insides of the trunking may also need passive fire protection too.
For built environment professionals, knowledge of fire compartmentation is vital.
Compartmentation is the principle of subdividing a building using materials with a specific resistance to fire, to help to manage and contain any conflagration that does break out. Usually, these subdivisions comprise walls, floors and ceilings.
Ultimately, provided that building elements such as these can halt or even slow the spread of fire and smoke, people have a much greater chance of safely evacuating a building in the event of a blaze.
Any breaches in the building fabric reduce its ability to prevent fire and smoke spreading. Therefore, where a hole is made in what is essentially a fire barrier or compartment, then fire-stopping – passive fire protection – will also be required. If not properly sealed, openings for cabling or other services in a building's compartments can create a gateway for fire.
Wiring Regulations 527.2.1 to 527.2.4 require that sealing for penetrations should match the fire rating of the building. However, it is important to note that some products such as expanding foam, silicone or caulk may appear to fill gaps but have no fire-stopping properties.
To ensure effective fire-stopping, specifying the correct sealant or product is paramount. Ideally, the products used should be chosen in conjunction with the manufacturer, to ensure that the installation as a whole meets all the passive fire protection requirements.
Figure 1: A lack of adequate fire-stopping measures can aid the spread of a fire © Gemma Denham
There are some key questions to consider when carrying out fire-stopping work around compartment breaches.
Specifications for fire-stopping often go into considerable detail, including concepts such as the natural expansion and contraction of materials in different conditions: substrates need to be robust enough to accommodate the methods of fixing, but may also need to perform under extremes of temperature and humidity.
It is for these reasons that fire-stopping in all but the simplest of cases should be regarded as a specialist activity, best assigned to dedicated service providers. Ideally, a specialist subcontractor should be involved at the design, specification, installation, and verification stages of construction. Clear and unambiguous communication is key here, contractors should ensure that they adhere to their contracts and also let sub-contractors know of their requirements too.
Ultimately, we all have responsibility when it comes to fire safety. It's something that should never be left to chance and, therefore, knowing where to direct your expertise as a building surveyor and when you need to rely on other specialists is essential.