Before any work begins a survey will be carried out on the property to determine the current state of the electrical installation and establish whether it is suitable to be worked on. This means checking that the water installation pipes are adequately earthed at the stop tap and the gas installation pipes are earthed at the meter. Checking that the existing fuse board/consumer unit provides 30mA RCD protection is also essential as it is now a requirement for most circuits. Without these provisions in place a certificate cannot be issued for any completed work, so it is essential that they are addressed as part of the job.
If your current setup does not have any RCD protection in place then a fuse board upgrade may be necessary.