Floor prep for tile?

[Ron Rohrssen]

I'm heavy into the demolition work on a higher end home with several hundred square feet of tile in place. 

My specific question relates to areas where I am removing tile, and plan to have someone else install tile in the same area.

I haven't consulted with a professional yet.

I'd like to hear from others on how clean and smooth the floor area needs to be for putting tile back in place. The mortar under the tile appears to be two layers thick. Did that happen during a prior retiling effort? I can't think of any reason why it's two layers.

If I can figure out how to add photos to this post it would really explain what I'm looking at. 

Try this link for a couple of photos. https://photos.app.goo.gl/eEaw8t6otqAfji7o2

[Nicholas W.]

So industry practice when setting tile on a wood subfloor is to spread thinset, lay cement board, screw it down tape the seams with mesh tape. Then spread more thinset and lay your tiles on that. That is what was done, it's a pain to remove but is the best way to ensure a stable floor that won't crack tiles and grout down the line.

The mesh you're seeing is encased in the cement board when you lay it, but not so much when removing it.