If sound transmission is a consideration when you are thinking of installing ceramic flooring tiles, consider this:

Natural Cork Underlayment is the underlayment of choice for sound control. Forever resilient, unlike the majority of synthetic underlayment membranes, it can be installed under any type of floor covering. A natural product which does not rot, it reduces and absorbs the moisture which might be created by condensation, preventing possible degradation of the floor covering and the subfloor.
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Synthetic underlayment membranes contain V.O.C.'s (volitile organic compounds) which, when subjected to various conditions of heat, light, and/or moisture, evaporate, or "off gas", and aside from the possibility of adding questionable organic compounds to the air you breathe, act to degrade the underlayment to where it is no longer doing its job. Natural Cork Underlayment lasts for decades.

You may also consider the use of Natural Cork Underlayment under ceramic floor tiles as insulation. We all know just how cold ceramic tiles can be. Some people avoid the purchase of ceramic tiles because they can be so cold underfoot. While the logical alternative is warm, naturally insulating cork tile flooring, or cork laminate flooring, it sometimes just doesn't work for you. Assuming that you would prefer NOT to fall back on carpet or vinyl flooring as an unsatisfactory last choice, you DO have a number of remedies that will allow you to enjoy the practical beauty of ceramic tile flooring.

1] You can wear slippers, which is generally recommended for indoor use on all floors anyway;
2] You can have an in-floor warming or heating system installed under your ceramic tile. A product such as NuHeat ( http://nuheat.ca/ ) is the luxury solution to cold ceramic tile floors;
3] If in-floor warming/heating is not the ticket, then Natural Cork Underlayment might be the best way to go. Natural Cork Underlayment separates ceramic tiles directly from cold concrete subfloors, or unheated crawl spaces, so that the tiles are merely "cool" unfoot, and not frigid;

Natural Cork Underlayment is a definite consideration when thinking of ceramic tiles; practical AND good for the environment!

Concerns about cork's softness are legitimate. There are some simple precautions that must be taken with cork flooring. Because it is resilient, heavy furniture can permanently dent it. It is suggested that you use high quality furniture pads beneath table or furniture legs. The maintenance of cork flooring is similar to any standard wood flooring. Simple periodic vacuuming of dust and grit will prevent scratches. As with any wood floor, water in excessive amounts can damage the flooring. Spills should be wiped up with a damp sponge or cloth. Cleaning should be done with mild, low-sudsing detergent, a damp mop, then wipe dry. Do not apply wax to a urethane finish.

A handy, informal way to check for excess moisture in concrete floors, prior to the installation of cork laminate or cork tile flooring, is simply to tape a plastic garbage bag directly and securely to the concrete using duct tape, and leave for about a week. When the garbage bag is removed, take a look at the side that was against the concrete and see if there is any moisture on it. Also, examine the concrete itself, and take note if the colouration where the bag was is different (darker) than the surrounding, exposed concrete. If there is moisture on the plastic, or the concrete IS darker, there is too much moisture in the concrete for a direct installation, which means the floor has to be sealed off beforehand. -- However, if you ARE concerned about excess moisture in your concrete floor, I recommend that you have a professional test for moisture content, and to recommend solutions.--