Use existing light switch to also power bathroom exhaust fan?

Question

The builder of my house neglected to place an exhaust fan in my guest bathroom. When I brought that to their attention, they replied that code only requires fans in bathrooms that don't have open-able windows. But the lack of one in my guest bath has always bugged me, so I'd like to add one.

But the bathroom is only "ganged" for the lightswitch that it presently needs. (And, the feeder from the circuit panel enters at that switch.) Would it be permissible to tie the exhaust fan into the switched side of that gang box, or am I required to give the fan a dedicated switch of its own?

Answer 1

You can use the switch to operate both the fan and light, if you so choose. In fact, this is a common feature in single user public restrooms. As long as the switch and wiring are rated for the amount of current, which unless you get a huge fan, it should be.

If you have the ability to install a new cable (or pull an extra wire, if the wires happen to be in conduit), you could use a device that has two switches that fit in a single gang box. Which would allow you to control each device separately.

Answer 2

I did this for a house I own, and tied the fan directly to the light. You don't have to run another wire from the switch - just wire the light and fan in parallel. Both were in the attic, so it was easy to run a wire from the light to the fan. If running a wire from the light box is difficult, you can add an extra box between the existing switch and the light that can feed both the light and the fan from the existing switch wire.