I have a new home with roughed in plumbing in the basement for a bathroom. I have purchased a fiberglass jacuzzi style tub. Besides framing, the manufacturer recommends some type of base to set the tub on, on top of the concrete floor, but is very nonspecific about what this material should be. The local home-improvement store rep suggested sand or mortar.
I'm thinking more like some type of spray foam that would form to the bottom of the tub and stay put; and also insulate.
Is there a standard method and what do you recommend?

I have a new home with roughed in plumbing in the basement for a bathroom. I have purchased a fiberglass jacuzzi style tub. Besides framing, the manufacturer recommends some type of base to set the tub on, on top of the concrete floor, but is very nonspecific about what this material should be. The local home-improvement store rep suggested sand or mortar.
I'm thinking more like some type of spray foam that would form to the bottom of the tub and stay put; and also insulate.
Is there a standard method and what do you recommend?
We first put down a large pool of "leveling cement" and pushed the tub down into it. Then, after that was set we used some of the spray foam that you mention to fill in any gaps. This has been in place for about 2 years now with no problems.

Jaimie

Hey dselcoda:

Jamie gave good information... but stay away from the foams as these can overexpand and could cause issues you just don't need.

In my area we primarily use a perlited STRUCTOLITE gypsum plaster to set our tubs in (see pic.)... great as insulator, too.

Structolite is super easy to mix... then install 2-3 inches deep along the "footprint" of the tub... then lower into mixture, fill the tub about 1/2 to 3/4 full of water for 24-48 hours and that tub will never be an issue for you.

We also have a rather handy guy online here that likes to use the premixed modified thinset mortar in a tub... his instructions are very similar to mine. I think his way may be easier in terms of mixing, but more expensive in terms of cost (structolite costs about $9.00/bag)... unless you have lots of left over from old jobs like he does... huh bob... ;)?

Hope that helps... Mark

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Do NOT use spray foam, yes it expands and fills all the voids but when you step in the fiberglass tub the foam will compact down and then there will be a void between the foam and the tub, next time you step in, it will crack and that's the end of your fiberglass jacuzzi.
I called the manufactuer on mine and they recommended using two to three 80lb bags of mortor mix. Mix it up dump it in the middle the length of the tub and set your tub down until its level and let it set. DONE

Structolite is the way to go. Make sure you use it. If you just set it on the subfloor, the empty spaces in between the foam feet that come attached to the bottom of the tub will be bending points when you step into the tub. They have no support and will eventually crack if you step in or your kids jump in the tub. I've seen 8 year old tubs that have cracked because people had just set it on a subfloor or even elevated the tub. The entire bottom of the tub needs support.

Let me add my two cents. I totally agree about not using foam as a bedding agent.
Foam consists mainly of air bubbles and in time they will compress leaving a gap.
Follow the above advice but forget the foam. Good luck, Tom