First the concrete needs to be clean, clean, clean. No oils, no paint, no coatings or adhesives. Then, you need to know if your slab has moisture coming through it. Take a clear piece of plastic, 2' x 2' and tape it to the floor with duct tape. Leave it there for a week, preferably after it has rained, to see if you get moisture. If the slab is dry, then you need to ensure it is a flat plane - no dips or bumps. If there are, grind down the hills, fill the dips with self-leveling compound. Then you apply an isolation membrane. There are paint-on as well as sheet-type membranes available. Then you are ready to install tile with thinset. If the floor has moisture, ideally you would fix whatever is causing the moisture problem and them proceed as above. If not, any flooring could fail. If the moisture problem is slight, you can fix bumps,dips and then use Schluter Ditra as your isolation membrane. It should handle slight moisture.

Thanks Jewel - that is the School of hard Knocks at it's best. A better plan is to have first the plywood - then some 1/2" Wonderboard Lite and then cover that with something like Laticrete's Hydro Ban Sheet Membrane. That way the tub deck is prepped for tile and would be acceptable even in a commercial steam shower environment. This is my last shower with tub deck. The tub is Kohler and the olive green material is Laticrete's Hydro Ban Sheet membrane. Installing it tight to the plywood was not ideal but again better than doing nothing at all. The shower side saw a heated bench get build and I used the sheet membrane to vapour proof the bench. The membrane then was used to protect the rest of the plywood tub deck from ever seeing water. Later a slab from Ceasar Stone was installed and I tilted the entire bathroom with a 1'x2' marble looking porcelain tile from I Marmi. Turned out nice.

Thank you for your help. I went over the floor inch by inch with a hammer, pliers, and a scraper with a point on the left side. I used the scraper to lift staples, and pull them out with the pliers if they did not immediately flip out. I pounded in every nail, and the nail heads, I just hammered them in until they were well inside the plywood. The store where I purchased the tiles said I needed to use the extra adhesive. As I worked, I kept wondering how the two adhesives would work together. I could not find an example of using the two online (youtube), so I called the manufacturer. She said that using an adhesive with the peel and stick tile would void the warranty. The tile cost me $400 for one room, and I have two more rooms and a hallway to go. WOW! No guarantee. I am waiting 48 hours now according to their directions. If you have any suggestions, I would appreciate them. I cannot use the planks because we did that in our dining room when we made it a dog room, and now about 4-5 years later, little spots of wood (product, not real wood) are coming up a little. That room was completed by my husband. They are barely popping up, but it is enough that I know I cannot handle that product. Sammy

What you first do with any tile floor installaion is compute deflection rating. In a wood structure that is always number 1 first step. Your photos show a mismash of poorly placed and wrongly installed plywood of unknown type/origins. So it doesnt qualify "as is" as a structural rated layer Your best removing this and doing things correctly. This includes the proper type subfloor on joists and then underlayment if its required and it all needs be Installed properly or your simply winging it and gambling. Id stop now and listen to your gut....and keep removing the junk down to joist, no telling what other joys youll find..