How to build a base for Travertine stairs?

[toffeeapple]

Hi all,

I am putting stairs in instead of the stepping stones for our front yard and hoping to extend it to the door which means to change the current tiles to the same Travertine.

Would someone be able to assist in guiding me on the base work prior to and if it's best to lay timber sleepers as a base instead of concrete?

This is the inspiration 

   

[Dave-1]

Good Evening @toffeeapple 

I am thinking along the same lines as @JacobZ  as in factoring in the levels of the patio area andn the side area. Trying to match up different levels can be a bit of a pain, ive struggled over the figuring out. I would try laying out packing at teh same level you expect your three surfaces to be and then step between them. if it feels ok then its doeable, if not then those concrete steps may need to go 😕

Dave