Hi I have an internal cavity wall after an extension which has some electric cables running to the consumer unit.I wish to upgrade my shower and need to have it rewired to 10mm twin and earth. The easiest route to the consumer unit is via this cavity wall from the attic ,is this allowed and does the cable have to be in a conduit?
Running cables through the cavity's in partition walls is common but the rules are complex. You need to be 50mm from outside of wall both sides or follow other rules as to how close to corners etc. The main problem is later when the route is forgotten one could drill the wall and hit the cable. Alternative protection methods are given like steel conduit and RCD protection. Work in bathrooms is covered by Part P and anyone signing the installation cert will have to had done the job or supervised it so I would ask who ever is signing the paperwork as competent person as to what routes they would want to be followed.