Minimum
England
Cable depth in a wall before extra protection is needed
50 mm
Measured from the finished surface on either side of the wall
A cable set deeper than this is considered out of drilling range; anything shallower needs mechanical protection or RCD cover.
Basis in regulation
How to check it on site
Where the depth cannot be achieved, confirm earthed capping or 30 mA RCD protection is in place and recorded.
Common failure
Chases cut just under the plaster with plastic capping only and no RCD on that circuit.
Effective from 22 August 2026. Last updated 23 August 2026. This is our editorial summary of publicly available regulation, not building control approval or a warranty determination.