A full rewire should mean that all parts of the electrics – that’s cables, circuits and accessories – are new. However you may wish for items such as switches and light fittings to be re-used and the electrician may wish to re-use a part of the wiring that is electrically sound, due to it being difficult to remove and replace. It is very important that you agree and understand with the electrician exactly what work is, and is not, being done before the work starts.
A partial rewire is a common situation if it’s not possible or necessary to fully rewire all the electrics. For example when existing cabling is suitable for continued use (this minimises the degree of damage and disruption), or where only a part of the electrics has suffered damage from a burst water pipe or similar.
If you are considering a partial rewire or an electrician offers it to you as an option, it is very important that you agree and understand exactly what is – and is not being– done before the work starts.