Installing Above Floor Rough-In Tub

[Jim Humphrey]

I'm new to the forum and was hoping to get some advice before I screw something up. I bought a Sterling Vikrell tub ( model 71111122-0) and I'm about to install it directly on a concrete slab floor.

The floor is off level by about 1/4". This is an above floor rough in tub so it sits on a plastic riser thing that lifts it up and has a apron extension installed for drain clearance.

Here's what it looks like:

My question is should I put mortar underneath the black plastic riser when installing it? My understanding of mortaring underneath a tub is so the tub sits in the mortar and it conforms to the bottom surface of the tub providing a sort of level supporting "cradle" for it. Is that correct? If so I don't see how I can achieve that with this type tub. I contacted Sterling and they were less than helpful and just said it was my choice to use it or not. Can you guys tell me how you would install it if it were you? Stepping in it I can already hear it making cracking noises. I just hate doing things the wrong way and regretting not asking someone before I did it. I've attached a couple of pics of the bottom of the tub. The riser is about 3 inches. Should I try sitting it in an extra deep mortar bed so that it squishes through the riser and supports the tub bottom? Any opinions would be greatly appreciated. I can't believe Sterling doesn't make this clearer.

Thanks!

 

[Terry]

I would be inclined to use the riser, and drop down piles of mortar mix that will spread out when the tub is dropped down. You need to make sure it's going in leveled and the mortar is meant to keep it at that level. I normally have a line drawn around the walls and the apron shimmed to where I will be wanting it, before I drop the mortar piles and and set the tub down into it. Typically, it makes for a very solid feel when it sets up.

If the floor is flat and level, I've used the felt pad and dropped the tub on that. If the floor is not working for that, I break out the mortar.

 

[Sponsor]

 

[Jadnashua]

That's a tough call. That thin grid will slice through any mortar, so to actually provide any real support, the piles would have to end up being quite deep so they hit the bottom of the tub itself. If you left the grid off and tried to do it just with mortar, you'd need quite a bit assuming you can't or don't want to cut the skirt.

I would be tempted to try to level the floor with something like Ardex Liquid Backerboard. Unlike most self-leveling cements, this one can be installed to a feather edge over plywood without needing a primer. FWIW, SLC is a misnomer...you do need to probably screed it level and flat, or you'll have some waves in it, and a rounded edge like after pouring a pancake. Make some guides that are perfectly level, then screed the material between them to flatten it off and fill in. Once it sets, you can take the guide out if you want. Some just screw some screws in, making the top of the flathead all level, and fill it to just that height. Again, though, a straight-edge is probably required to get a good result for most people. At a 1/4" max, and the small area, one bag should be more than enough. Prep, though, would be critical. The stuff cures quite fast, so you can work on the tub install later that same day.

Once the area was flat and level, I'd then see how the tub sits and whether it creaks. Maybe some felt on top of the leveling material.

 

[Jim Humphrey]

Thanks for the info guys. I'm going to try it both ways and see how it goes.

 

[Reach4]

Thanks for the info guys. I'm going to try it both ways and see how it goes.

Both ways? Schrodinger's mortar?

 

[Jim Humphrey]

Both ways? Schrodinger's mortar?

Haha I won't know which way I did it until after I observe it done.

 

[Kata]

I would be inclined to use the riser, and drop down piles of mortar mix that will spread out when the tub is dropped down. You need to make sure it's going in leveled and the mortar is meant to keep it at that level. I normally have a line drawn around the walls and the apron shimmed to where I will be wanting it, before I drop the mortar piles and and set the tub down into it. Typically, it makes for a very solid feel when it sets up.

Thought I'd resurrect this post to get a little more clarification, as I am putting in what looks to be the same tub. We have a floor joist where our drain needs to go, so we had to have the above floor drain to have a bit more room to work with. I've never put in a tub and with so much space between the tub and the floor, I thought the typical "bed of mortar" would not be sufficient. Mostly because those plastic risers look and feel cheap- not strong enough to support the weight of the water. How much mortar do I need to put in? With the riser, there is about a 4 inch gap between the tub and floor. Do I fill it all with giant piles of mortar? I'm thinking six(ish) individual, fat, 5-6 inch high piles so it is deep enough to go through the risers and contact the actual tub? Will supporting in six (ish) places be enough? should I put enough mortar that once the tub squishes it and spreads it it touches the entire bottom of the tub (going up and around the black riser)? Am I way over thinking this?

This simple project has turned very complicated with that stupid floor joist in the way.

 

[Jadnashua]

I don't think I'd use mortar in this circumstance...if the floor wasn't already level, I'd level it first. I'd then verify that the tub sat there without rocking, flexing, or squeaks.

 

[Kata]

I don't think I'd use mortar in this circumstance...if the floor wasn't already level, I'd level it first. I'd then verify that the tub sat there without rocking, flexing, or squeaks.

Let me clarify that the installation instructions require mortar (or a felt pad)

 

[Bannerman]

We have a well known contractor here in Ontario that had a TV show dealing with corrections necessary due to improper work performed by other prior contractors.

One of the methods he promoted when installing a bathtub is to use a few cans of expanding foam insulation to support the tub as opposed to mortar. With the additional riser space under your tub, I anticipate the tub could be set in-place and fully leveled, then the foam could be injected using a straw tube applicator connected to each spray can valve. If some weight is placed within the tub, that should ensure the expansion will not lift the tub.

Dawbacks may include the 'stickiness' of the foam and the potential for expansion into the drain connection area, but that maybe controlled with some blocking to act as a barrier.