What is the joist span? Will they support any ceramic tile?
Are you asking about structural steel channels?
C4x7.25 for 16" spacing
It's late and I have to go to bed, but there is the size. Good luck with your project!
That just barely works for deflection and the wood will be over stressed because the steel isn't stiff enough to attract enough load away from the wood.
Angle 4x4x3/8 is the other option.
No problem. I'm happy to help. Good luck with your project.