I had some slope to the floor, and used grout to even it
up, then I put a layer of thinset down, then put a panel
of 2" foil-backed foam down, then the tub in place and
quickly filled it with two garden hoses, and watched the
extra grout get pushed out. I left the water in over the
weekend, got back and siphon-drained the tub Monday
night, removed the tub and cleaned up the "removed"
grout, and there was never a doubt about it being solid
enough.
I wanted the foam to be at the bottom because I didn't
want heat being transferred away. My wife appreciates
that.
But I like the idea of doing it with expanding foam. It
would have been quicker, I could have taped plastic to
the bottom to prevent the foam from attaching to it, in
case I ever wanted to take it out. Not likely.

Hey, wife prefers a long soaking bath with Epsom Salts.
She hasn't even insisted that I connect the pump. Too
many have already told her how the water gets cold
quickly when the pump is running. Two big pumps
sitting in the garage, candlelight and dimmed light in
the bathroom.

The world is good.

On Feb 17, 2:24*pm, Oren wrote:
On Wed, 17 Feb 2010 09:15:16 -0800 (PST), "

wrote:

http://clients.teksavvy.com/~bsaking/Reno/CIMG6258.JPG

I'm the odd man out. When my tub was installed I filled the tub and
then used expanding foam under the tub. Five years later - no problem!

I let the foam cure a couple of days, before I drained the tub. It is
solid, no flex in the bottom of the tub.