question on leveling by patching compound, diflection for stone and other things.

[Tony_nubee]

Hello.
I'm getting ready to put tile down in another kitchen and need your expert opinions on some things. My diflection (based on the calculator answer) are well above what is needed for stone but that's because of my big joists. However I have only one sheet of 3/4 plywood covered by appropriately installed cbu.
1. Can I put stone (travertine) down even though I only have one sheet of ply under cbu? (My diflection is mid 800s)
2. The floor has a wave with certain spots as low as 3/16" in 10 feet. SLC won't do since floor is not level. I was thinking of planipatch, Ardex feather finish or Henry 547 patch. Planipatch is locally available and I already have henry 547 but ardex ff takes time to get. Do you recommend one over another? I'm hoping for something that is as thin/loose as possible so I can screed easily over reletivly large areas.
3. Do I need to add milk to powder and also prime the surface when applying over CBU (hardi).
4. Do I have to tape my cbu gaps with regular thinset before applying patching compound.
5. I'm using laticrete 4-XLT and tuscan leveling so I can get thicker thinset under tiles for more play room as far as leveling and lippage. How much playing room can I expect? Want to see if I have to flatten areas that are 1/16" deeper for example. (12x24 or 24x24 porcelain or travertine based on answer to my 1st question)

Thank you so much in advance as ya'll have solved many miseries for me.
Thanks
Tonylp

[cx]

Welcome back, Tony.

1. Can if you wanna, but the industry standard requirement is for a double layer of plywood, regardless the joist spacing. Each layer properly, and differently installed.

2. Have you read the installation instructions for each to determine whether the manufacturer recommends the product for your installation?

3. Depends upon what you're applying. See #2.

4. The manufacturer of the CBU knows nothing about your plan to use a patching compound. You would follow all the directions for one before using the other. If the CBU manufacturer requires that you fill and tape the joints, you'd fill and tape the joints.

5. If you flatten your floor sufficiently, and if your tiles are sufficiently flat, you should have no difficulty achieving a flat tile installation. For tiles the size you have the requirement for the floor is no deviation from intended plane of more than 1/8" in ten feet nor 1/16th" in two feet. That's a very flat floor and you'll be very glad to have it when you start setting those big tiles.

The industry requirement is for 3/32nds" of mortar under the tile when set. The maximum depends upon the mortar manufacturer.

My opinion; worth price charged.

[Tony_nubee]

Thank you CX. I did read the instructions for Henry 547 and didn't see anything regarding adding milk for CBU. don't think I saw it in planipatch either but haven't read the ardex yet. Maybe I should call them since I didn't see anything regarding CBU install but I think it should be ok. I will tape my cbu gaps with thinset per instruction. Since the wife haven't settled on a tile yet I have not read any manufacturer install recommendation for any tile yet. We were really hoping for travertine but as you mentioned not having 2 layer of ply bothers me. Plus some of the travertine I looked at, I was able to break like a cracker with not much force as they had more than ideal amount of holes in the back. I think they were the cheap kind .
Thanks again