Code of Practice for the Electricity (Wiring) Regulations - 2009 Edition

(b) Where cables run as a span between beams, trusses, etc., rigid
support throughout their entire length should be used. One of the
fixing methods of cables hung under beams is illustrated in Figure
25(2).
(c) Cables crossing an expansion joint should be formed into a loop
such that any movement in the joint should not stress the cables.
(d ) For cables running on surface of walls or structures:
(i) buckle clip should only be used to fix cables having an overall
diameter not exceeding 10 mm.
(ii) saddles and cleats may be used if the diameter of the cable
exceeds 10 mm.
(e) (i) Cable saddles and cable cleats should be secured by fixing
screws and should be provided along the entire cable route at
regular intervals. The spacing between adjacent saddles or
cleats should not exceed the values given in Table 25(3).
(ii) A saddle or cleat should also be provided at a distance not
exceeding 150 mm from a termination and from both sides of
a bend.
(f ) Where cables are installed under floors or within false ceilings, they
should normally be supported and fixed throughout their lengths to
the permanent ceiling or floor and provision should be made for
access to the cable for inspection and maintenance. Such cables, if
exposed to the risk of penetration by nails, screws and the like,
should be protected by an earthed metallic sheath or enclosed in
earthed steel conduit or trunking securely supported.
(g) Where a wiring system passes through elements of building
construction such as floor, walls, roofs, ceilings, partitions or cavity
barriers, the openings remaining after passage of the wiring system
shall be sealed according to the fire resistance requirements of BS
476:Part 20 or equivalent required of the element concerned (if any).
(h) The internal bending radii of PVC insulated stranded copper cables
should not be less than the values given below:
Overall Diameter of Cable, D
Not exceeding 10 mm
Exceeding 10 mm but not
exceeding 25 mm
Exceeding 25 mm
Minimum Internal Bending Radius
Non-armoured Armoured
157
3D
4D
6D
6D
6D
6D