... that is the question, and here is my situation:

I'm getting ready to drop in my Kholer 60" one piece fiberglass shower (no tub) on my basement concrete floor. I've asked two different contractor friends whether or not I should set in concrete. One said definitely, without hesitation. He said I could set in wet or even dry concrete, with the condition that the dry concrete would eventually harden from the moisture from the air.

The other contractor looked at the bottom of the unit and saw that it is reinforced with about 1/2" plywood, which is integrated into the fiberglass floor, and said that it probably did not need to be set in concrete. We looked at the installation instructions that came with it and it did not say to use any form of support under it... just set it in place and install the drain.

The bottom does have blocks on the sides and back that it would sit on, so the center of the floor would be suspended over the slab floor somewhat... about 1/2" to 3/4".

I would like to get more input on whether I should use the concrete. I guess I am hesitant to use it as I am concerned that it would setup prior to getting it situated into the final resting place, and then I would have a mess on my hands. The thing is large, awkard and heavy and will take a few people to lift it into place.

Thanks... Randy

I vote no concrete.

I think less than 10% of professional contractors/installers would agree.

Kohler is reputable; I'd stick with their installation instructions and recommendations.

Thanks rickj.

Randy

I see now that my fingers were working faster than my brain.

I'll guess you know what I meant, but just to clarify:

I meant to say

"I think less than 10% of professional contractors/installers would agree that you should set it in concrete"

Good luck in your project!

Well, I called Kholer and discussed it with one of their reps and they said that because this particular unit has already been reinforced on the bottom, a concrete bedding support is not necessary or required.

So I'm going with the NO vote. I appreciate your advice.

Check what our top plumber said at https://www.askmehelpdesk.com/showthread.php?t=12940

Your tub sounds like the ones he says don't need concrete.

Thanks labman,

I've decided to add the support after all. It can't hurt, and it certainly may help to keep the floor from creaking as it ages.

Hi Randy,
Here's what the manufactures have to say. A fiberglass or plastic shower stall or bathtub should be bedded, which means support is required under the base so the floor does not flex or give when someone is standing on it. If the unit is installed without proper support then in time the drain seal will rupture and cause a leak. Putting cement or mortor under the floor when it is installed gives it a solid platform , which prevents flex in the floor. Without this support, the flex will cause movement at the pipe connection resulting in cracks in the base and leaks at the drain.
If the floor of your shower flexes or gives, (even a little bit) when you step into it the floor should be bedded for support. If you don't support the floor it will eventually rupture the seal between the lip of the drain and cause a leak. The time to take care of this is at the time the shower's installed. You may use wood to shore up the floor or puddle cement or mortor under the floor before you set it and let the shower floor squoosh it down. If you use cement let it set up and cure overnight good luck, Tom

Thanks Tom,

I've already decided to add the support, but I do appreciate your input. Even though Kholer, the manufacture, told me that because it is already reinforced it didn't require the bedding support, I've decided to do it anyway... an ounce of prevention is worth a pound of cure, seems to fit well here.

Randy