Can you install floor tile over padding? The floor tile is standard tile that will require grouting.
I'm concerned the tile and/or grouting will crack due to the padding. The purpose of the padding is to reduce the noise of foot traffic in the room below. Sound dampening padding is fairly thin, and not nearly as thick as carpet padding.
In almost all cases this is a no. There are waterproofing systems you can use but not flooring pad. When you lay your tile the pad will move a little and cause issues. In essence with a pad you are creating a giant floating tile floor.
Note: To reduce sound from the floor you want to do two things.
The padding you are thinking about leaving might reduce sound by 1%. Sound is due to weight disbursement - generally speaking. A 200 pound person running around will make sound. 10 pounds of padding underneath them will have no affect. I am sure someone can comment on the science of this. But the two things you want to do are create a buffer (pad is thin and almost no buffer) and keep your joists from moving (pad does nothing at all there).
Yes, there is a type of pad used exclusively for tiling over a concrete floor or over uneven subfloor. The pad stops cracks in the concrete from telegraphing through and eventually causing tiles to pop up or he grout to prematurely erode away. A cork pad is just 1 type of padding material used for this type of application. The pad is first bonded to the sub-floor with thinset, then the tile is laid in a thinset bed atop the pad.
Epoxy grout does not "give". Epoxy grout is exactly what it sounds like. It's a chemical reaction between two chemicals, and most companies use aramid fibers added in the mixture for strength that's almost indestructible. You have to work very fast with epoxy grout: you have about a 20 min working time after mixing it and the more it's mixed the shorter the working time gets. Plain epoxy grout is smooth, but you can get a sanded version. You literally have to grind out epoxy grout with like a Dremel, while normal grout is a variation of Portland cement that can be scraped out with a knife.
I've used a firm cork subfloor material under large format tile which, installed over 1" marine quality plywood and 1/4" self-leveler, lasted for the last eight years with no issues. I will mention that a friend who is a guest of ours often tips in at over 450lbs and has done no damage. I did use an epoxy type grout designed to have slight give. My point? Yes there are new products out there that are getting better, some of the corrugated style noise dampening total area seal products also serve to dampen some noise. Check manufacture recommendations for noise reduction. It will be referred to as a number followed by 'db' rather than a particular percent since they have no information on your structure or type of noise...even this is a bit seductive when researching because of so many acoustic properties in different homes and the hubris of many manufacturers.. good luck!
