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.

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.