Cable entries

The entry of cables from the outside to the inside of a building sometimes causes
difficulty. There must obviously be a hole in the wall which has to be tight round the
cable and which has to be sealed to prevent dirt, vermin and moisture entering. Whether
the cable is an armoured type laid directly in the ground or whether it is drawn into a
duct, the most practicable way of making the entry into the building is by means of an
earthenware duct built through the wall below ground level. When the cable has to bend
up to rise on the inside face of the external wall, a duct bend can be built into the wall.
After the cable has been pulled through the polythene or earthenware duct, a seal is
made round it within the duct with a bituminous mastic compound. Normally this is
inserted from the inside of the building. The essential requirement is to make the seal
watertight; it will be readily understood that a seal which prevents water coming through
will also stop dirt and small animals. In difficult cases one can make a metal plate to
overlap the earthenware duct with a hole in it of a diameter to be a push fit on the cable.
The duct is filled with mastic, the metal plate is pushed over the cable to cover the end of
the duct and is screwed back to the wall, and the edges of the plate are then pointed with
mastic. This construction gives an effective water seal.