Tub Creaking

[Weekend Handyman]

Hello:

It's me again ... I've done something dumb this time. I installed an acrylic tub without a mortar bed (I know) and it is creaking. In my defense, the directions did not call for one.
- It does creaks mostly when I am stepping into in.
- It seems to be most prominent in the middle and along the apron side.
- It does not creak when I sit on the apron.
- It does not creak when I step directly above the legs.
- My best guess is the tub is flexing when I step on a part directly supported underneath and this is causing the creaking. It feels solid and I do not see any visible deflection.
- I have access to under the tub from the back wall (i.e. opposite the apron side). It's a little tight. Maybe 1-1.5 in off the floor on the drain end and maybe 3 to 3.5 inches off on the other end.

Some background:
- It's a Maax Bosca acrylic tub (so decent quality)
- It is supported by two legs and the apron.
- The tub is on a self leveling cement pad.
- After the SLC, there was still a dip of about 1/8 under the apron. I addressed this by shims side by side to fully support the apron.
- All shim are glued to the floor with PL Premium.

Possible Solution:
- I am considering filling the tub with water and spray some low expanding foam under the tub.
- I was going to slide under a garbage bag to avoid gluing the tub to the floor.

Questions:
- Is this the best approach?
- Are there alternatives I should consider?
- Regarding spray foam, what brand / product is best for this application?

 

[Reach4]

I have access to under the tub from the back wall (i.e. opposite the apron side). It's a little tight.

Could you shove in many lumps of mortar in sandwich bags? Make the balls big enough that they get squished to the right height on the way in.

 

[Sponsor]

 

[Weekend Handyman]

Could you shove in many lumps of mortar in sandwich bags? Make the balls big enough that they get squished to the right height on the way in.

I had thought about that. It would be a tough go. The clearance on the drain end is quite low. To make matters worse, there is an extra piece of OSB (presumably part of the mould) that would make sliding the bags under extra challenging.

 

[Weekend Handyman]

Update: I still have an issue, but at least now I know what it is.

As mentioned, I shimmed the apron. So far, this has worked out very well. This AM, I figured out the apron is rubbing on 2 of the 30+ shims (about a 2 inch section). This seems to account for 99% of the noise the tub is making. When I apply some pressure to that point of the apron, the noise goes away.

I think I am going to just put a thin bead of silicon on that spot to try to keep it from moving and possibly to lubricate if it does. Thoughts?

 

[Reach4]

I think I am going to just put a thin bead of silicon on that spot to try to keep it from moving and possibly to lubricate if it does. Thoughts?

Consider removing the rubbing first, perhaps with a multitool. Then caulk.

 

[Weekend Handyman]

I am pleased to report the tub is now silent ... sure am glad I found the source before I started messing with after the fact mortar, spray form, etc. I will do a mortar bed next time tho ... just was not confident enough in my skills, this being my first tub install.