Working on a bathroom remodel and have a couple of questions>
I want to add a radiant heat floor system. Can I branch the electric coming from one shower light switch and make it a double switch? one for light, one for floor system? Walls are still open so I can easily get to them.
Also, on a ceiling light junction- can I expand this wiring and use it for a base for recessed lights ( 4-6)
Thanks! Lisa

You need its own feed from the electical panel for the floor heat. Do not branch any wires for heat.
As far as using the ceiling fixture as a source of power for other lights. Not suggested either unless you know the wire size, the amount of other fixtures that are on this branch and weather or not the breaker or fuse will handle the new load.
You cannot simply branch out of the center light fixture box to the new recessed lights and then cover the old light box over. Assuming your not going to use the existing center light again. Also code has limits to how many wires can be in a box. Even if it looks like there is enough room. It may not pass code.
My suggestion is to have a electical contractor wire these fixtures for you. Much safer and can be done much quicker. Do not forget the GFCI outlet. Ideally on its own branch with the shower light connected to it. Much safer and less likely to trip being a 20 amp size when using hair dryers etc.