Does my acrylic/fiberglass alcove tub need a mortar bed?

[Dave&Carley]

The tub has a sheet of osb (I'm guessing) covered in the fiberglass material and 6 high density foam blocks for legs (see photo)

The subfloor was mostly level, but I needed to shim under 4-5 blocks to get it fully level. I used the plastic shims and set them with high grade adhesive. Is this enough support or should I pack some mortar under it while I've got access from the back wall?

 

[Terry]

If the six legs are supported well, you should be okay. How does it feel when you step in the tub?

 

[Sponsor]

 

[Jadnashua]

The hassle with fiberglass, versus say cast iron, is that it isn't all that stiff. The glass fibers can bend, but if you exceed their limit, or stress them too often, just like bending a wire back and forth, eventually, it can break. So, it doesn't hurt to help reinforce the bottom of the tub to make it feel sturdier and eventually, last longer. Whether you need to do it, somewhat depends on the tub. Getting the thing to sit flat is one thing, but you REALLY want the rim to be level, and mortar can help with that. It can also make a difference whether the people using the tub are 40# children, or 400# adults, or maybe a pair of them, if you want to get frisky!

 

[Dave&Carley]

If the six legs are supported well, you should be okay. How does it feel when you step in the tub?

It feels pretty solid for the most part, but the most recent time I needed to step in the tub, it made a creak noise I didn't like which is what got me looking into the mortar bed.

The hassle with fiberglass, versus say cast iron, is that it isn't all that stiff. The glass fibers can bend, but if you exceed their limit, or stress them too often, just like bending a wire back and forth, eventually, it can break. So, it doesn't hurt to help reinforce the bottom of the tub to make it feel sturdier and eventually, last longer. Whether you need to do it, somewhat depends on the tub. Getting the thing to sit flat is one thing, but you REALLY want the rim to be level, and mortar can help with that. It can also make a difference whether the people using the tub are 40# children, or 400# adults, or maybe a pair of them, if you want to get frisky!

I went ahead and picked up a bag of mortar mix earlier with the intension of just doing it, it's not going to hurt anything to have extra support under the tub, especially since it IS big enough for the wife and I lol

Thanks for the input

 

[Reach4]

Bed is a bad word for putting mortar under a tub, because it may mean something to you that is not good.
See https://terrylove.com/forums/index.php?threads/first-tub-install-please-help.84586/

I would put balls of mortar into sandwich bags with diameters that are maybe 1.3 as big as the space. Shove them in as best you can to cover the space intermittently. The bags help keep the mortar from drying out, allowing the mortar to harden properly. I am not a pro.

 

[IAm_Not_Lost]

Would high density closed cell spray foam be appropriate? Seems that some installers use that a lot with good success. You could just hit a few spots to add columns of support.

 

[Terry]

Would high density closed cell spray foam be appropriate? Seems that some installers use that a lot with good success. You could just hit a few spots to add columns of support.

If you use that, fill the tub with water first. You don't want the tub to be lifted upward.