One cautions: an older house is likely to have asbestos in vinyl flooring and pose a health risk if removed improperly.

Here is a link that might be useful: Floor tile removal

It sounds like you can go taller without height concerns,so if your subfloor is in decent shape, i would use self leveling and take care of the low spots, then install backerboard over the entire area to accept your tile.

If your existing floor is bouncy and has give, you would want to consider ridding that problem as ceramic tiling over a flexible floor will give you constant maintenance issues at the grout joints.You want a solid base for cearmic flooring, otherwise it proves unreliable.

Shimming the joists/subfloor,you stand a chance of creating a void that will cause excessive flex and give as well. This all depends on how serious and how much shimming it would take, but it sounds by your description that you have a pretty substantial drop in areas.

If your existing floor framing is fairly solid, then i would go the self leveling route.You might have to put a barrier over the existing subfloor planking in order to keep the leveling compound from running down into any cracks or holes. It will find any avenue of escape,as it is a fairly liquid mix until it sets.You will probably want to put down 15# felt over the entire area before the backer board any how, so this should be a decent barrier to keep the leveling compound from escaping. Staple the felt down well.

I generally dont recommend ceramic tiling over a wood framed deck unless it is rock solid.

Sierraeast, thanks for your recommendations; they are truly helpful.

Are you talking about asphalt roofing felt when you say 15# felt?

Yes, saturated felt. If you wanted heavier, go with 30#.In fact,if you go this route,use 30, as it isn't that much more dinero.

Another thought i didn't mention was that you stated the possibility of going as tall as 1-1/4" with plywood. If you have no height concerns, you can lay down the felt, cover that with riblath wire mesh, and lay down a 1" bed of mortar.Leveled out,it will naturally be thicker in the areas that are now low, but would give you a decent,level base for the tiling.

I layed ceramic over the existing subfloor in a room that we use for our parrots.The room was added on before we bought it and has a sturdy floor system.They used osb for the subfloor,and due to inexperience on my part, i layed the tile directly over this and it has failed in places.If i would have known at the time, i would have went the mortar over felt and mesh route at the advise of a floor installer friend. We didn't have backer board in them days,but even putting down plywood over the osb would have been better. Oh well, live and learn.I'll get around to taking it up and doing it right one of these days(years)!

Best of luck on your project whatever course you take!

Thanks very much for the response.

I just did a bit more looking and there actually is a layer of plywood above the subfloor planks. For some reason, the portion between the register and the wall did not have ply but a gap instead. I thought this weird and dug around on the other side of the register and there was the ply.

So... should I leave the existing ply in if it's in good condition or should I just take it up and put new ply down? I'm guessing it would be better to put new ply down because then I could make sure the planks are down nice and tight and then I could also make the mortar bed like you mentioned and then secure the ply to/through that. The plank plus ply measurement is 1-1/4" thick. Once I take out the vinyl and the old hardwood I'll have the build the floor up (including the tile) another 1-1/8" as the total of all the layers (plank, ply, hardwood, vinyl) is 2-3/8". So assuming I'd use the same thickness ply I'd have this 1-1/8" left. My tile is 1/4" and the hardibacker I bought is 1/2" which leavs 3/8" left that the mortar/thinset will have to take up. Is this enough room; should I drop down to 1/4" hardibacker?

One more thing:

I'm looking at my invoice from HD (which I'm learning more and more is probably the last place to make important purchases) and I see that I purchased Versabond Bonding Mortar and Flexbond (not Versabond-Flex); 150lbs of each. I haven't picked them up yet (as well has the hardibacker) but I have purchased it all. It's been a few months since I've purchased it and I forgot what was for what (the asst. manager did tiling for 20 years so he recommended all the products). I'm pretty sure the Versabond was for below the hardibacker and the Flexbond for above. If I decide to use a self-leveling compound would I still use the Versabond mortar over top of the self-leveling compound or any other kind of thinset over the self-leveling compound. When you say mortar 1" in the low spot do you mean to use a product such as this Versabond mortar or another product?

If you are using a self leveling product, that would be used first to level out the drops and un even areas.Im not familiar with the brands you mentioned, but the bonding mortar for under the backer board will go over the leveler and under the backer board.With you measurements being close, keep in mind that it is easier to build up to the height that you want, so 1/4" backer should be fine.If it drops a little low, you can build it up with your mortar/ thinset ,but not too heavy. It sounds like you would only be building up about an 1/8" or so, that should be okay.

If the existing plywood is in good shape, you can make sure the plank boards beneath are tight by simply screwing down more fasteners through the plywood. Just make sure the screws are long enough to go through the ply,planks ,and into the framing members.This could save you a step from having to remove the existing plywood.

If your still wondering about your Versabond/Flexbond issues, jump over to the bath forum and ask that question. A pro tiler named Bill Vincent will most assuredly jump in get you straightened out. Also the John Bridge website is a haven of both pro and highly skilled DIYers that are very willing to share.

Thanks spanky,

I discovered the John Bridge forum yesterday and I've been active over there and the members have been extremely helpful; thanks!