Date: 2/27/2008 7:07 am EDT
Excellent observation and a great question!
The short answer is, the type of movement you are seeing should be fine. And you may notice a slight "squishiness" even after the floor is grouted.
Now for the longer answer. What happens is the entire floor becomes a large "membrane" of sorts floating over the top of whatever surface you have. With the QuietWarmth heated underlayment below, there will be some "give" in the floor, much like you'd see with a floating laminate floor. (By the way, I've had QuietWarmth under Avaire in my bathroom for just a few weeks shy of 2 years and we absolutely love it.) You may even see this same type of "membrane" type movement without a separate pad underneath because the rubberized grid on the bottom of the tile provides a similar but less extreme cushion. With this type of movement, you can understand why it is imperative to use the Avaire Flexible Grout - if you were to use a cement based grout, I can guarantee failure. Just think how rough your car would ride if you used stone tires..... Come to think of it, I believe they used to use stone/wood/steel tires way back when. Thank goodness for progress! But I digress.....
Let me shed some light on the difference between this movement and the movement we warn against in the instructions such as you would see if a tile "rocks" in place over a hard surface. If you were to place a Avaire tile on the concrete subfloor and it were to "rock" that means there exists a "fulcrum" point under the tile which can eventually result in that tile cracking or possibly overstressing the grout. Without seeing the actual movement you are describing, it is difficult for me to tell exactly which type you are experiencing. If the tile were to "rock" directly over the concrete, then putting a QuietWarmth pad under the tile means the fulcrum point still exists - and that would not be good.
Do you recall the brand of the other pad you are using as a filler? Is it the same thickness as the QuietWarmth?
For test purposes, we've actually installed Avaire directly over a commercial carpet (low nap) with a concrete slab below. That floor is in a commercial shipping office and was installed 19 months ago. To date, we have not experienced any problems with the tile or the grout on that floor. Now, we do NOT recommend installing Avaire over commercial carpet (someone would see the word "carpet" and attempt to install Avaire over a 2" shag....), but it demonstrates the resiliency of system.
If you have additional questions, please don't hesitate to call us and we'll one of our experts help you assess the situation.
Please send us pictures when your floor is finished!
Thank you for buying Avaire!