I have this 54" Swiss Madison brand alcove tub going into the new bath. It's acrylic, looks like OK quality, but the only 54" alcove tub I could find locally. Here is a link to the tub: [swissmadison.com]

The tub comes with adjustable feet to help with installation, which seems like a good idea. The installation instructions also call for the tub to set in mortar. I emailed the manufacturer about type of mortar and placement, and they replied that the tub feet should be set in mortar, that the mortar should not touch the tub bottom. Either thin set or Structolite is OK. The instructions say to set the tub in place, drill pilot holes thru the tiling flange into the studs, remove the tub and apply mortar, stand in the tub to compress mortar under the feet to return tub to original position so that tub can be screwed to wall using the pilot holes.

It seems to me that all the mortar would be squeezed out in this process, and if mortar is not required to support the actual tub basin, what is the point? I asked if construction adhesive could be used to secure the feet in place and all they said was not following directions voids warranty.

Anybody have experience installing a tub like this? How would you install it?

you are in between a rock and a hard place.
the bottom of the tub has a nice piece of MDF giving it strength.
i don't think the company would tell you to do (or not do) something if it was going to cause them a warrantee problem.
so the bottom looks plenty rugged the way it is. drill the pilot holes as high as possible.
also use 100 % silicone caulk when installing the tub drain and flange.

From reading the descriptions it seems (to me) what they really want are those five acrylic feet (the wider part) to be supported by mortar. The levelers are necessary so the tub rest on all five legs (in case uneven tiles cause some legs to be higher/lower. Imagine if the entire floor is perfectly level the levelers would not be needed and you sit the tub right on the floor with the levelers removed...all five fat feet will make full contact with the floor is my guess the design intent. The mortar extends the fat feet to the floor.

If that's the case I would expect the mortar to be squeezed out of the levelers' bottom and I would make sure to pack the mortar all around completely embedding the levelers making five elephant feet.

Between thinset and Structolite I would opt for Structolite it's very light weight and strong. However this stuff dries very fast, I used it on plastered ceilings and from the moment you scoop the powder into a pail for mixing you have 15 minutes before it starts to set up and become not so pliable. Also it comes in 50 pound bags so you are only going to be using 3 pounds.



Edited 1 times.

Another thought...may be the mortar base's main purpose is to ensure all five legs touch the floor solidly.

If someone carelessly install the tub without adjusting all the legs so they all touch the floor, or if they got four feet to touch but when adjusting the fifth one they raised that one too much and cause one other foot to be raised a tiny amount, one you can't tell visually but when the tub is full of water suddenly it wobbles 1/16" on one side enough to cause a strain on the tiling flange. So the mortar is just extra insurance to make sure all feet touch the floor, if a gap exists under any foot, the amount not squeezed out and you compress standing inside makes up the difference.

Sum I think that's right. Looking at the leveling feet, they may only designed to level the tub during installation, not support it over the long term. You need a pile of mortar to build up support around the feet to help carry the load over the long term.

I emailed the manufacturer this question:

"Hi, I just purchased this Voltaire 54x30 alcove tub, and the installation instructions mention setting the tub in a mortar bed (step 5 in the installation instructions). In looking at how the tub is made it looks like the adjustable legs would eliminate the need for mortar? Regardless, what type of mortar is recommended, modified thinset or Structolite? Also should the mortar be placed under the adjustable legs or under the tub between the legs? Any additional info would be appreciated,"

This was their response:

"Thank you for contacting Swiss Madison! We apologize for any confusion. The feet are included to ensure proper drainage and that the unit can be leveled on all sides.

We suggest utilizing a thin layer of mortar to set the adjustable feet into during installation.

This is not intended to meet the bottom of the tub or completely cover the feet.

At this time, we do not have a specific mortar recommendation for the installation of our units as long as the mortar used is safe for bathroom installations.

Please feel free to notify us should you require further assistance.

Thank you!

Best,
Swiss Madison team"

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Sum, your answer makes complete sense, use the mortar to build up the legs so the weight of the tub isn't solely on the adjustment screws, but here the mfr says not to completely cover the feet.

The issue is they don't WHY you need the mortar...if it's to keep the adjusters from turning over time, I could do that with a dab of construction adhesive on the bottom of each foot. Any additional thoughts and ideas welcome.

Sum, based on your thoughts I sent one more email to the Swiss Madison team:

Me: "Hi, one more question on the mortar. Is the mortar supposed to build up over the leveling feet so that the main tub feet are supported by mortar and not the leveling feet?"

Here is the response I received:

Manufacturer: "We suggest utilizing a thin layer of mortar to set the adjustable feet into.

This would not be to completely cover the feet.

The mortar would not need to reach the bottom of the tub itself, only form a thin layer to depress the feet into."

Seems like a waste to mix mortar just to put under the feet, I could accomplish the same with some construction adhesive. I'm reading that it's always a good idea to use mortar to bed the entire bottom of the tub regardless of what the mfr says. I'm also seeing a popular alternative of plumbers using expanding foam under the tub in place of mortar.

Any thoughts/comments appreciated.