Has anyone ever tried this? I was thinking of trying it on a new staircase we have leading to the basement. Bottom edge would be covered by the oak tread, top by a piece of cove trim. Therefore the only place there would be grout would be between the tiles. Whats a good material for the risers pine, MDF, tile board and how thick 1/2" or 3/4". I was thinking of trying 1/2" tile board.
Are you building the stairs or are they there with no risers?
I would just use 3/4 ply for the risers (If you are adding them) and then use mastic too attach the tiles to the ply. If you have a prebuilt stair it will likely have risers of pine. Same thing, use mastic on the pine.
We tiled our stairs, but had to use DuraBoard to build out the Riser to allow more of a flush surface with the tile. Keep in mind that the tile if going from the bottom Tread, to the next, leave some space for the Oak molding, if placing over the top edge as a protector.