Holes made in Walls and Ceilings
Compromising Fire Barriers
Walls and ceilings in buildings may be designed to provide
fire resistance. Penetrations in walls and ceilings made to accommodate mounting boxes or recessed lighting may compromise such a Fire Barrier.
Particular care needs to be taken when cutting holes in the same cavity ie. the same space between two studs. An example of this would be back to back switch boxes or recessed lights either side of a wall within the same joist space.
In such cases recessed boxes and light fittings should incorporate integral fire protection or be fitted with a proprietary fire protection pad (intumescent) capable of forming a 30 minute fire barrier.
The sealing of penetrations around cables, conduits or trunking may be required to prevent the spread of fire. An intumescent filler or seal should be used for this purpose.
Intumescent material expands when subjected to heat and can act as a barrier in case of fire.
Consideration must also be given to the routing of ducting for extract fans. Fan ducts may be routed through different areas of a building and therefore breach fire barriers.
The duct should be fitted with proprietary fire protection such as intumescent seal or wrapped in a suitable intumescent based liner.
Also where wall mounted extract fans are installed through cavities it is important to install non-combustible ducting to prevent fire from entering the cavity.
An informative guide on this subject ‘ESC- Best Practice Guide 5′
is available from the Electrical Safety Council
Note:
Holes made in the structure of a building may also compromise:
Structure- Part A
Resistance of Contaminants & Moisture- Part C
Resistance to the Passage of Sound- Part E
Conservation of Fuel & Power- part L
The Building Regulations Part B deal with Fire Safety in dwellings.
BS7671 Regulation 527 refers to:
The Selection and Erection of Wiring Systems to Mimimize the Spread of Fire.
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