There are various situations where adding a second switch in an existing electrical junction box could also be useful. Sometimes there just isn’t enough room so as to add another junction box and even to replace a single-gang box with a double-gang box. Other times, adding a second switch for a ceiling or exhaust fan or another light circuit in an existing room may be problematic, especially if the walls are concrete or CMU (Concrete Masonry Unit) construction. Regardless, installing two light switches in a single box most often requires less work than installing a new junction box. Installing two light switches in one box might be completed in a few simple steps.