Currently I removed the old vinyl floor, and found the old black adhensive on the plywood floor is very difficult to remove. After asked several guys, the current plan is applying a thin layer versabond fortified thinset on the old adhensive with flat trowel side, then putting a wonderboard cement board on that and nail it on the wood floor. Is this plan ok??
after I read the instruction on the versabond, it said it can be used on cutback adhensive, does it mean I can directly apply the ceramic tile on the thinset mortar without wonderboard? thanks for any info.

That would depend on your subfloor system, but even if it "technically" okay, I would still use a 1/4" cement board.

Basically, you must have two layers of plywood with a total thickness of 1 1/4". Most floors do not have this.

Even with two layers, you're depending on the bond between the thinset and cutback adhesive. A cement board with thinset underneath, nailed/screwed into place, is your best insurance for a successful installation.

Is your current subfloor plywood, and do you know the thickness of it?

The correct way to install the wonderboard is to apply a fairly wet versabond on the plywood with a 1/4 inch notched trowel and set the wonderboard into that then nail or screw it down. This eliminates the potential for voids or humps that you would get with a skim coat with a flat trowel.

Tiling directly on cutback adhesive is fine with a good modified thinset, but like K-man said, the subfloor needs to be rigid enough.

Yes, I think it is plywood, I can see it consists of about seven thin layers. it is about 7/8"

Most likely it is a single layer of 3/4" ply. You'll need a CBU for that.

Also important to check out your joist system to make sure it's up to par. Use the "maximum span calculator" at the top left of the page. Are the joists on 16" centers?

Do I need to wait versabodn dry before screw it down?

yes. joists is 16" centers. Sorry, I am really a newbie to these stuff. what is CBU? and I checked span calculator, lots of stuff I am not sure which I should select.

No problem. If everybody on the site was a pro, we'd have no questions to answer.

Go ahead and give us the specs on your joist system. We need to know the size of the joists (2x8, 2x10, etc.), the species (SYP, Fir, etc.) which is usually stamped on the joists somewhere. There should also be a grade stamp on there, which is a number. Then we need to know the longest unsupported span of the joists. Simply, this is the longest span that your joists run with no support from underneath them. There may be areas of your house that won't be getting tile, and those don't matter. But if a soon-to-be tile area is over a joist, we need to know the unsupported span of that joist.

CBU = Cementitious Backer Unit, or cement board. It's referred to by many different names, usually by the brand name: Hardibacker, Durock, WonderBoard, etc. The thinset underneath needs to be freshly combed out and the CBU set into it immediately, then screwed/nailed down immediately. You can start tiling over it as soon as you're finished screwing it down, no need to wait.

the only stamp on the joist I found
"A.F.RA 43
S-P-F SEL
S-DRY STR"

and longest unsupported span is 140" and it is 2X7“

So you have two by eight joists. SPFsel stands for Spruce pine fir select structural. S dry means it was kiln dried to 14% moisture. You're ok for span, though if you have easy access to the floor system you could install a couple of lines of solid blocking between the joists to stiffen things up a lot.

Does that span calculator used to decided maximum size of ceramic tile I can use?

You can use any size. The larger the tile size, the more important factor is how flat the floor is.
The span calculator only deals with wood subfloor structure. You use it to see if your existing structure is capable of supporting tile or stone that's within the minimum deflection criteria for either ceramic tile, porcelain tile or a natural stone installation.
You should have a minimum rating of L/360 for ceramic and porcelain and a minimum of L/720 for natural stone.

Currently I placed wonderboard and screwed it to the floor, but some screws are not totally into the board, they are a little higher than the surface of the wonderboard, is this ok? thanks

Those high screws can cause you problems with getting the tile to lay flat. Worst case scenario, you could have tile cracking when it's resting on a screw head.

What kind of screws did you use? Are they deck screws and do they have a phillips drive or a square drive, or something else?

The way I fix those stubborn screws is to drive one into the floor next to it and pull out the high one.

thanks, I tried, cannot make them totally flat with cement board, maybe 1-2 mm is ok? the screws I use is Buildex Rock-ON, phillips screw. it is said it is specially designed for cement backerboards.

Are you sure the rock-on screws you bought are for wood?
You really should try to get them at least flush to the surface.
Could be a problem if thinset coverage while setting is minimal.

Impact style screw guns work best for setting screws. A regular screw gun will usually strip the phillips heads before they are flush to the surface.

The normal trowel notch used for floor tile is 1/4 by 3/8 inch. this gives you a thinset thickness about the thickness of cardboard. any bumps bigger than 1/8 inch (2 mm.) will hit the bottom of the tile. get a counter sink drill bit and counter sink the protruding screws slightly. A quick fix is to give the protruding screw a good whack with a hammer and then sink another one about two inches away. This is a common problem with cement board screws, which is why I usually use epoxy coated deck screws.

tried to make the screws less than 1mm higher than the cement board. put tile on yesterday, looks ok now. how long should I wait before apply grout?

Is the same structure and same cement board good to apply marble?

16 to 24 hrs before grouting.
Input all the data into the span calculator but change the deflection criteria to L/720. If your existing joists span more than the allowed in the calculator report then you would not be able to install marble without reinforcing the floor structure.

I would use Schluter Ditra instead of the cement board if your floor meets their minimum requirements.

Stone installations should have joists that meet the span requirements with a minimum 3/4" plywood subfloor plus a 1/2" plywood underlay and an underlayment layer of cement board or a membrane like Schluter Ditra.

Deflection of single layer subfloor material between the joists is one of the big issues for a stone installation. Two layers of plywood at the correct thicknesses helps reduce this problem.

thanks, I put spruce-pine-fir, 2x8, No.2(I assumed), floor joist, L/720, 16"spacing in the calculator. it give me 9"9. looks like it is not good for marble. My current is 4 layers vinyl, they stick very well. does this help for marble?
My plan is put a layer of mesh net and staple them, then apply motor for marble? if this is not good for marble, I will just go with ceramic tiles.

Before you do any tile installation those 4 layers of vinyl and the underlay must go.

The mesh net you are referring to, is it Mapeilath plastic mesh or are you talking about galvanized wire lath? If it's the wire lath /scratch coat then that's garbage. Go to the Home Page and on the left side there's an article About Scratchcoat. http://www.ontariotile.com/scratchcoat.html
Take a look at it, then decide if you want to risk an installation with that method.

I am lucky I asked here before apply mental lath. I learned the lath way from my neighbour, their contractor just finished their new tile floor with lath over the viny floor. But even in Rona, it is called "lath floor galvanized".
In Rona, I also saw a "synthetic lath", is that good for flooring?

And what kinds of choices do I have over the vinyl floor,
1) put a cement board or underlayment wood over vinyl and screwed them?
2) Ditra ?

You should heed RC's advice and get rid of all four layers of vinyl. You don't really know what's underneath them, and that many layers is bound to have some cushion to it. Better to put the effort into removing it now, rather than just going over them and causing in installation failure.

Looks like I cannot avoid that job. :-(. thanks for help.

I read the "tile installation" pages in this website where it talks several substrates. I am confused after read mud and scratchcoat. In "mud", it said "Mental lath is used to enforce the mortar bed.". In "scratchcoat", it said "This method is meant only for walls." So, mental lath and wire mesh are different stuff? what's the different between these two? thanks

Metal lath,expanded metal lath and wire mesh refer to the same type of product. The differences are in the size of openings and the thickness of the mesh. It is made up of sheets that are slit and expanded to form small diamond shaped openings.


Mud and lath is mostly used for doing walls,as you saw in the tutorials.