First you have to find out if your engineered wood is designed for floating. Not all are. If it is and the tile is glued down tight you could install right over. Is this below grade? or above?. If above you generally just use a standard underlayment then float the floor over. If below then you may need the moisture retardant pad.

Thanks for your response, boxers.

I'm not entirely sure that the wood we have is designed for floating. The merchant told me he has had it floated in some places, but I don't want to interpret that to mean it was originally designed to be floated. I'll have to make some calls to find out about this.

The floor is above grade. We're a 1-story house on a slab in San Diego.

What is a "standard underlayment"? (In other words, could you tell me a brand/model?)

Thanks. At this point, I'm tempted to just apply the moisture retardant epoxy on the vinyl tiles and hope it stays.

when I worked for Bruce some floors could be floated but the tongue and groove was different in floors we designed to be floating. A standard underlayment is like what they use on laminate a thin layer of foam. There are thicker more sound absorbing type underlays. Its the same product used with laminate flooring. Some have a moisture backing which would double as your moisture barrier. I'm going to let one of the other experts suggests brands to you.

I'm not a flooring expert, but we did float our floor in our house (over vinyl tile). As the others have suggested to you, first make sure that your floor is made to be installed as a floating floor.

Our house is a concrete slab, with old vinyl tile under it, probably from the 60's is our guess. Definitely has black adhesive, and it's a pretty good guess that they have asbestos. We didn't even bother checking it -- we figured it would just be easiest overall to do a floating install regardless, as the thought of dealing with glue seemed way too messy and tough for us to handle.

We used an underlayment called QuietWalk -- it has a moisture barrier attached on one side. They sold it at our local Lowes, so it was easy to find and purchase. You basically just roll it out on the floor, cut it, and tape the pieces together with a special moisture-barrier tape.

The installation was a fairly easy process -- our brand (BR-111) requires that you use glue in the tongue and groove, so with my husband and I working together, I would glue the piece of wood, hand it to him where he was kneeling on the floor, and he would hammer it into place. At the end of a row, he would measure how long the piece needed to be, jump up and go cut it, we'd put it in place, and the process would continue. We became like a well-oiled machine :) Doing a floating floor like this is really quite easy, and I don't have any problem recommending it to a DIY-er, even ones that were brand new to home projects, like we were.

One caveat -- our floors do have a slightly "springy" or hollow feel to them. I think a discerning person can probably tell that the floor is not affixed to the flooring underneath. Personally, we don't care or mind -- they look beautiful.

I want to install some engineered wood flooring over the vinyl tile (on a concrete slab, above grade) in my 1950's house. The vinyl flooring likely has asbestos, so I don't want to pull it up, but it is not level enough to just go over. I was planning on levelling with some self-levelling compound, but I don't think it will bond well to the tile (I even tried stripping the finish and priming the tile with a recommended primer, but the primer just beads on the floor). Does anyone have another suggestion? I'm thinking about putting down more of the underlayment in the low points of the floor, but that is going to be painful...

"Floor Muffler" is a good brand underlayment. Do not use more layers of underlayment for your low spots. Fix your unlevel subfloor. Fine sand can be inexpensive way to fill a low spot on your subfloor.

"I've been reading that adhesives won't stick very well to vinyl tiles because of the black "cutback" adhesive under it."

That may not be entirely true. VAT tiles adhered with cutback adhesive may or may not be a suitable substrate for your wood. It all depends on how well bonded to the slab the tiles are and how much moisture migrates through the slab and out between the tile edges.

There are one-step moisture retarder/wood floor adhesives now in the marketplace. These probably are not available through your local big box store.

As a professional, I can usually very quickly determine if a VAT floor on a slab is well-bonded and stable enough to install any kind of floor over it. But, this has come after many years of experience.

You're going to have to do some more research and make a "best guess" I'm afraid.

I guess my problem is not installing the floor - it is levelling over the vinyl tile (I'm going to float the floor).

I was thinking about putting down an embossed vinyl tile leveller, such as 1800:

http://www.robertsconsolidated.com/files/pdf/datasheet/US/1800%20Adhesive%20PDS.pdf

and then use a cement-based self levelling compound over that, such as levelquik:

http://www.custombuildingproducts.com/ProductCatalog/SurfacePrep/SelfLevelingUnderlayments/LevelQuikRS.aspx

I tried the primer that levelquik recommends on top of the vinyl but it just beads (so I'm guessing it will not form a good bond). But I've put down 1800 on the vinyl on smaller spots and know that it will stick.

what do you think?

OK...I didn't read your initial post carefully and didn't notice that your tiles are 9" X 9"...that probably makes them asphalt tiles. Very difficult indeed to get something to stick to asphalt tiles; asphalt tiles may have had wax incorporated into the product.

Test your proposed system and see if it will bond well enough. Since you're floating the floor, I don't see why you'd have a problem, as you would not have the pulling effect of anything bonded to the LevelQuikRS.