we are interesting in using larger travertine tile
use latex modified thinset morter and an underlay called ditra bond the ditra to the patio and the tile to the ditra this is for independent movement for both I'm not sure about using travertine as a patio its one of the softer natural stone and pores
most tile is put down on cement so your alright there. go to your hardware store and thy will fix you up but you need a mortar that is good for out side like what you would use for a shower don't for get to put a sealer on it or all your hard work will be for nothing
