Mapelath over vinyl flooring

I have a 5/8" plywood subfloor, with 3/8" K3 and vinyl flooring (Armstrong Designer). The vinyl is in great shape and the floor is sound. I have heard about a product called Mapelath (from Mapei) that can be applied directly over vinyl. When used with Mapei Ultracontact mortar, this is supposedly a guaranteed installation. (According to Mapei, this installation approach can be done over as little at 5/8" plywood over (19.2)" joists.) Has anyone used this Mapelath product? Any feedback would be appreciated.

I'll swear by Mapei products. They're almost exclusively all I use any more, but back when the mapelath first came out a year ago last spring, the area Mapei rep gave a seminar on the stuff at the local Dal warehouse. I watched him do his demonstration, and after he was done, he was talking about how this stuff is TCA tested, and passed with flying colors, and so forth. I asked him what would keep the tile, especially on a weak floor (such as the one you described), from cracking all to hell at the seams of the sheets of lath, that this seemed like just a new twist on the lath and scratch method that TCA has found to be so problematic. He couldn't give me a good answer. He said he didn't know-- just that it had been through "extensive testing".

I wouldn't trust it any more than any other plastic or methal lath method. That is to say, not at all.

5/8" sub on (19.2) spacing?

How high do you bounce when you walk across this?

What Bud said, also, get rid of the vinyl and add more plywood, would also like to know the unsupported span of these joist, are they I-joists?

I don't care if this floor was as solid as could be. The fact that this floor is weak to start only makes matters worse. Till I see something From TCA in the handbook advocating this method of installation, I won't use it. There's been too much reported to the contrary.

I am shaky about any installation over vinyl no matter what the circumstance.

Thanks for all the replies. Indeed, they are I-joists. The floor is actually very solid, and the room I was looking at was only about 90 sq ft.

I previously removed the K3 and vinyl from my front entry and added another 5/8" ply before tiling that area. The vinyl and K3 removal was a NIGHTMARE. Thus the reason for wanting to go over the vinyl. Another alternative that DAL tile indicated was to install 1/4" Hardibacker over the vinyl and tile over that. Nothing is ever easy.

The manager at MY local Dal warebouse and I have gone round and round about this, because he ALSO says no problem. I've shown him in black and white where TCA recommends that this is not adviseable, and he shows me the side of the thinset bag where the manufacturer says it can be done. Then I pull a pail of mastic off the shelf and show him where it says it can be used in wet areas, and he just shrugs his shoulders and says that the manufacturer has stated that they'll back up the installation, My question to him was how many times has he seen a manufacturer's rep go on a jobsite and say whatever it took to cover his company's butt, and he agrees, but at the same time, he takes the official stance that if the manufacturer say it can be done, then that's the advice he gives..... with the exception of the mastic in wet areas.

So Mapelath is out and Hardibacker over vinyl is out. Given the K3 is glued down with LOTS of PL400 and MANY staples. Is there any easy way to remove it? Maybe a demolition hammer with some kind of blade on it?

Better late than never, I used it over vinyl, 16" on center joist 5/8 wafer board. I layed a 2" accent strip around the perimeter of my 10'x10' entry with 13"x13" field tile layed on a diagonal with dot in the corners. The point? Three weeks after I layed the tile I rode my 700lb bike with my 200lb a*s on it in to the den for some tlc. NO BROKEN TILE, NO CRACKED JOINTS, NO 2" ACCENTS POPPED UP. 1yr later no prob!

Tile can be installed over vinyl.

For the record everyone here except me thinks its a bad idea.

I have had success when the vinyl is down very well.
I say try it

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.Remove the vinyl!

It appears to me that a hack has emerged

We have been using mapelath over vinyl and in other circumstances recommended by mapei here in Grande Prairie, AB, Canada for well over three years. We have found this method not only problem free (assuming you follow they're recommendations) but much simpler and more economical than plywood. There is a learning curve though because Ultracontact is a completely different type of thinset than what we are used to. It is very sharp and the mixing instructions are very different. No, you don't bounce, and the warranties are good, even for a DIYer

Mapelath over Lino? Isnt that a bad bad idea? If the lino is on 1/4 inch plywood, and that plywood was only ever stapled down and not screwed down, how can mapelath/ultra contact make it suitable to tile over! Doomed to fail wouldn't you say?

Why are listening to some hack from 6 years ago.

Oh and yes, BAD IDEA.

I was going to suggest Mapelath until I read this http://americanflooringsystems.net