When installing a steel tub, is it really necessary to reinforce base with thin set, mortar or joint compound?

I know it's a must for sure when installing fiberglass tubs. I'm also pretty sure its not necessary at all when installing cast iron.

What's the story with steel tubs?

If reinforcement is necessary, what should be used as a base for steel tub and how thick should base be. Tub is being installed over new 3/4 subfloor, followed by thin set and cement board.

PS: I know that steel is the least popular of tubs among the pros, but there's no way I'm getting a cast iron back up the stairs. At the same time, I've heard too many stories of fiberglass tubs needing repair due to cracks.

Info is appreciated. Thanks!

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When installing a steel tub, is it really necessary to reinforce base with thin set, mortar or joint compound?

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Some steel tubs already have plastic bedding installed. If yours doesn't then I would bed it in as I installed it.
Steel bathtubs 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 mortar under the floor when it is installed gives it a solid platform , which prevents flex in the floor. Simply puddle or make a ball of thin set, cement or mortar and place them around under the tub and bear the drain. Without this support, the flex will cause movement at the pipe connection resulting in cracks in the base and leaks at the drain.
I have installed hundreds of steel tubs in condos in my area. That was over 20 years ago and haven't had to change any out yet. Good luck. Tom

OK Thanks!

Will spread mortar under floor of tub before connecting drain. What did you mean by "bear the drain"?

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Originally Posted by aacfh53

OK Thanks!

Will spread mortar under floor of tub before connecting drain. What did you mean by "bear the drain"?

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That should have been, "NEAR the drain" Sorry, Tom

Duh on my part!

Thanks again.