This chapter discusses the overall plan for modernizing an existing installation, including upgrading to a larger service and adding new circuits. It also offers problem-solving approaches to the specific challenges you are likely to encounter. There is little difference between old and new work, except that in old work there are a great many problems of carpentry. The problem is to cut an opening where a fixture is to be installed, and another where a switch is to be installed, and then to get the cable inside the wall from one opening to the other with the least amount of work and without tearing up the walls or ceilings more than necessary. One house to be wired may be five years old, another a hundred years old.
Different builders use different methods of carpentry.
Every job will be unique. No book can possibly describe all the methods used and all the problems you will meet. Watch buildings while they are being built to get an idea of construction at various points. In old work, good common sense is of more value than many pages of instruction. In general, old work requires more material because it is often wise to use ten extra feet of cable to avoid cutting extra openings in the walls or to avoid cutting timbers.