floorguy: Thanks for your response. Actually, we don't have any moisture barrier below the subfloor. As I described in my post, the layers right now go like this (from bottoms upwards): soil -> concrete slab -> wooden subfloor I checked under the wooden subfloor (on top of the concrete) and there is nothing in terms of moisture barrier or any barrier at all. What used to be on top of the subfloor was linoleum, by the way. So I intend to finish this as follows: soil -> concrete slab -> wooden subfloor -> cement board -> radiant heat cable (NOT pipes) -> mortar (to seal the cable within) -> floating locking floor So where would the moisture barrier/noise/cushioning layer go in this structure, assuming I cannot touch the bottom three layers (soil, concrete slab, and subfloor)? Thanks for any help!

I would peel up whatever vinyl sheets are there. Then scrape the rest with a scraper. Tile needs a good substrate or the tile could crack, your grout break up, or tiles become loose. I would use something like Schluter-DITRA (Mike Holmes uses it constantly) orange waffle. I used a blue mat I found in the tile section of HD. It's intended to quiet tile for upstairs flooring, but it had a sticky tar like backing that made it ideal for laying over old laminate that wouldn't come up. Here is a link that might be useful: Schluter-DITRA orange waffle

Transitions need to be discussed with the flooring installers before things get going. It is possible to get a flat connection with two PERMANENT floors...but with a floor that is floating (expending and contracting a whole schwack between winter and summer) and one that is permanent (grouted tile) you are most likely going to have to put up with some sort of raised transition. There are ways to get in a schluter edge at that transition, but it needs to be put in at the SAME TIME as the tile...which sounds to be a bit too late. A quick t-mould and you are done. It may not be what you wanted to see...but with the types of floors being installed, it is the logical solution.

OK...if you REALLY want to go over this, you are about to spend more money that it would cost to remove the tile: #1: Flooring professional will THOROUGHLY clean the tile (with big machine and strong detergents); and allow to dry (1 day or more if you include the dry time) #2: Flooring professional will rough up the tile (big sanding machine - tapping off all cupboards, air vents, walls, etc) - clean up (shop vac) will take another or two #3: Cement topping (like feather compound) will be added to the floor to ensure you achieve "flat and level" (grout lines are NOT flat; tiles/stone are NEVER flat nor level); should take a few days including cure times #4: Light sanding to knock down any pumps; vacuum once again #5: Begin installing vinyl planks #6: Homeowner will add appropriate light-blocking products on windows that allow direct sunlight onto the floor (you are welcome to put down an indoor/outdoor thermometer in the sunny patch to record TOP temps in summer. Most vinyls HATE heat above 85F. That is tough combat with windows that are older than 10 years. The Korean-designed vinyl products can reach much higher temps (EZ Lay or Drop N Done) and are specifically designed for in-floor radiant heat. Of course their price tag reflects their ability...but it's what is needed in this situation. Which type of in-floor radiant heat do you have? Electric (wires), hydronic (water/gel/oil) of forced air? Do you have a primary heat source or is the radiant heat the ONLY source of heat in your home?