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Casing
One or two layers of VERMICULUX® board (see TABLE 3 for
thickness) screwed face to edge at 200mm centres.
Cover strips
VERMICULUX® 25mm thick x 125mm wide, fixed over joints.
For single layer duct constructions, cover strips should be fixed to the external faces of the top and sides, the
bottom strip must be inside the duct.
For double layer constructions, board joints are staggered minimum 100mm and cover strips need only to be fixed to the
inside at the bottom of the duct. Cables should be supported on trays but these can be omitted if the bottom internal
cover strip are located at no more than 600mm centres.
Supports
M10 threaded rods fixed by means of expansion bolts into the concrete soffit. Tensile stress in rods should not exceed
6N/mm2.
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VERMICULUX® boards can provide up to 90 minutes of fire
resistance level (FRL) for cables and services enclosure with external fire exposure in accordance with the criteria of
BS476: Part 20: 1987 thereby maintaining the functionality of essential cables in a fire.
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TABLE 3
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Required FRL/Thickness of board for cable enclosure
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FRL
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30 minutes
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60 minutes
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90 minutes
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Type 1 dimension
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≤100mm x 100mm
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Thickness
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30mm
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50mm or 2 x 25mm
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2 x 35mm
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Type 2 dimension
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350mm x 170mm to 760mm x 300mm
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Thickness
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25mm
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45mm or 20+25mm
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2 x 30mm
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