How you do the infill depends on the eventual elevation differences you'll have between the hex you want to keep and whatever subfloor surface you'll have to work off of once whatever flooring you have under the tub is removed. Cement board is a fine material to tile off of. If you need more depth than that, then you can add plywood under the tub, then cover that with cement board, then tile on the cement board. When you install the cement board, you first have to bed it in thinset (thinset spread on the subfloor with a 1/4" notched trowel), then you screw or nail it down. The thinset isn't there to bond the cement board to the subfloor. The fasteners do that. The thinset simply fills in any micro-voids between the cement board and the subfloor which eliminates any future vertical deflection between the two materials. You can use unmodified thinset, about $10 a bag, between teh cement board and the subfloor. If you want to keep the same size hex under the tub that you have on your floor, as has been mentioned, you can add a border or transition strip on the floor, then install your new hex under the tub. You can transition with a solid inset piece, or you can add a dot or key (or some other) type of transition: As has been mentioned, sometimes trying to match things perfectly doesn't look so good when you can't get a perfect match. In that case, you can keep the metarial (marble) and shape (hex) but change the tile size. Add a transition strip, then tile with larger hex, say a 3" marble hex, under the tub. Then there is the option of keeping the material ant aproximate tile size, but changing the shape. For example, going to an obong hex: Or you can shift gears completely. You have options. Probably too many! lol If you want to keep things familiar between the new tile and old, try to keep two of the three properties similar; tile size, tile material, tile shape (pattern). The more you diverge from "matchy-match", the more unique the tub space can become. And do realize there is nothing wrong with that. If the other elements in the bathroom allow it, the tub floor space and the tub alcove can become a design element on its own.

First, I am a DIYer so take this advice for what it is worth. 1- if you do succeed in removing all those tiles and reapply them to that greenboard, in a couple of years they will all fall off again anyway. I had that in a condo we were renting in the city a few years ago and as soon as the smallest bit of water gets through your grout (and it will) that board will rot away quickly, the tiles will pop off one by one, and the entire project will need to be done again. 2- if you call in a professional now, they will not apply to that greenboard either (not if they are reputable anyway) and will charge you for ripping it out and installing cement board. Even if some DIY people would apply tile to green board, the green board has now been compromised by you removing the tile. Green board is only coated drywall. The green coating is a waxy coating that is supposed to keep it water resistant. If you look at it, do you think it is going to be water resistant now? If I were you I would cut or score around where the tile currently is and was and remove the green board and tile. I would go buy cement board and screw it to the studs. It goes up just as easy as drywall, you patch it like drywall, and then you have a nice EVEN (your tile is not going to lay nice on that current surface), clean surface that is waterproof to go ahead and install your new tile on. And you are not going to have to worry about having to re-do it in a few years. I promise the extra time spent will be well worth it down the road. It is up to you whether or not you want to call someone in or not. You should know that it will be more than the professional simply laying tile though, he will be charging you for re-doing the backing also. Best of luck, Kalindi

Long story on why I had to do it this way but my tile person says there won’t be any damage to wood. The current tile is marble and it’s cracked in many spots. Also, it looks very dated and we are hoping to replace it and get a more contemporary look. I’m looking for the right color in porcelain but having very hard time finding a good complement. Do I go darker than wood? Do I go lighter? Here’s a few photos some samples.

In an effort to minimize visual "noise" in a relatively small space, may I suggest matte black. And to support the suggestion, may I offer the following before and after: Same fireplace (and space). Now looks bigger due to the matt black tiles surrounding it. And the decor does not have to be modern for this visual to work. Generally, in design, a good rule of thumb to apply liberally is: the less is more. Good luck in your project. Looking forward to seeing the after pictures.