To add to the discussion, I was just told that I have a floating pad in the back. Something similar to this:
http://midcenturymonster.files.wordpress.com/2011/03/16-back-patio-under-deck.jpg
He's saying its a floating pad and the tub can tilt because of the immense pressure a spa will put on it. Is that true?
I don't know what a "floating" pad is. But, it what's under the pad is what matters.
I would worry about it cracking and splitting before I would be concerned about it tilting.
I will say that there's no way I would put a hot tub on the deck in the pic. Not beefy enough. If the pad under it is that skimpy in terms of materials and base, it probably is not solid enough.
For a concrete pad to work properly, it has to be done right as indicated by several members here.
If a concrete pad has to be removed and if you're not accustomed to running a jackhammer, don't have a way of hauling off debris and have to hire any concrete removal done it'll probably cost you as much to have it removed and hauled away as it did to put there in the first place if not more.
I'm so used to mine being on a deck, that the benefits of a concrete pad are lost on me. A raised treated deck just above the ground level would work well also, as suggested by topline Mike.
However, situations are different and either way will work fine if it suits you.
All true and the more extreme the climate/season changes are the more care that should be taken in a properly installed slab.
