With the increasing demand for recessed electrical sockets and switches in buildings, contractors need to be aware of the need to firestop these penetrations. Rupert Coggan examines the problem and offers some solutions.
Approved Document B of the Building Regulations is very clear about the need to protect penetrations in fire resisting walls. Yet the penetrations which represent both the greatest number and highest total open area of penetrations are sometimes ignored – these are penetrations for recessed switches and sockets.
Approved Document B 2006 states: “If a fire separating element is to be effective, then every joint, or imperfection of fit, or opening to allow services to pass through the element, should be adequately protected by sealing or firestopping so that the fire resistance of the element is not impaired.”
Fire protection of penetrations in walls is important in all building structures. It is even more important, however, in timber framed constructions where the structure of the building is vulnerable to any fire entering the wall cavities, leading to potential catastrophic collapse.
The penetration made by a standard, single recessed switch or socket box has almost three times the open area as that of a typical ceiling downlight, and we all know how much effort is put into firestopping downlights! In many ways, the fire protection of switch and socket boxes is even more important than that of a downlight, as they are usually present on both sides of a cavity wall. This would allow a fire to both enter and leave the compartment, whereas a downlight only penetrates one side of a two part element i.e. the ceiling but not the floor above.
Multiple opportunities for fire
Given that almost every room of every building has multiple switches, sockets, data points, telephone points and aerial sockets, it can be seen that the scale of the potential risk for fire spreading is huge. It is also estimated that the amount of hard wiring within buildings will treble over the next 10 years, meaning that there will be an ever increasing number of wall socket and switch boxes.
Although fire protection may be the main benefit of firestopping switch and socket penetrations, there is also a growing need to reinstate the acoustic performance of the wall after it has been peppered with holes. In many cases the firestopping solution will reinstate the full acoustic performance of the wall. Each solution needs to be checked to see if acoustic data is available. The process of firestopping could also achieve the additional benefit of reduced air leakage.
The traditional method of fire protection for any type of switch or socket box has been to encase the penetration with a fire resisting material, usually plasterboard, which produces a secondary barrier behind the recessed box. This is a perfectly valid and sensible approach although like all on-site construction, is dependent upon the skill of the person actually undertaking the work.
There are now a number of fully manufactured and semi-manufactured purpose made solutions for switch and socket penetrations from several manufacturers. These include pads to put inside the drylining box, ‘putty pads’ that can be moulded around the box, and fully intumescent pre-formed covers. These solutions can be fitted during or after construction.
The correct selection of whichever solution is used is important to make sure it will work in the application in which it is being installed. It is vital that the fire test data covers the application. For example – has the product been tested with penetrations on both faces of the wall and with or without cavity insulation? This all needs to be taken into account.
Added value
As with all types of penetration made for electrical services, it is the responsibility of the electrical contractor to ensure that the switches and sockets are fully fire protected wherever it is required. The usual reasons for electrical contractors not firestopping penetrations are either due to ignorance of the legislation, or because of financial constraints. The ignorance factor can be overcome with ever more publicity. The financial argument can easily be turned on its head, as most people who are fire protecting their electrical penetrations are very happy with the additional income which this produces. So they simply add value to the job by being the electrician and firestop installer. As an electrical/firestopping contractor, you can be sure of doing the job correctly, meeting the legislation, potentially saving lives and getting more income per job.
In summary, the need for the firestopping of recessed switch and socket boxes in fire rated walls is clearly required by Building Regulations, and the ever increasing number of such penetrations makes this action all the more crucial. There are a number of methods of achieving the required firestopping, from on-site solutions to pre-manufactured products and in many cases, the need for improved acoustic or air leakage will also justify using the fire protection solutions.
Rupert Coggon is business manager at fire protection manufacturer Tenmat Limited. www.tenmat.com
