Bathtub Installation - Leveling

[Freddie]

I'm renovating my bathroom and have already removed everything, updated the plumbing, replaced the OSB flooring with 3/4" plywood, etc..

I have the tub ready for installation and the drain/ overflow plumbing is done...on the tub but not yet connected to the trap.

You can see by the above image that there are 5 feet on the base of the tub from which the manufacturer has recommended you shim to level the tub. Given that all the walls are closed on the backside this is not the preferred method and even then I think this would be long and tenuous.

The tub has no place to put in a level support board along the back for at least a starting point and the manufacturers instructions do not specify this either. Just level with the feet as you see above.

So, given all this and a lot of research I've come up with the following plan:

1. Locate the high spot in the floor and use that to set a level around the walls to which to match up the top of the tub screwing flange.
2. Lay down some plastic over the areas where the tub feet are.
3. Put down some sand mortar mix below the tub feet
4. Put down plastic over the mortar (prevents sticking to tub feet incase I need to remove tub later on)
5. Place tub down onto mortar.
6. Adjust tub into mortar until the top level of the tub flange is level with the line made on the wall in #1 above.
7. Add a few screws to the screwing flange to hold in place.
8. Use level and a few shims along tub skirt (if needed) to ensure tub if totally level.
9. Let dry for 48 hrs.

Does this make sense? Any suggestions?

thanks,

 

[Jadnashua]

The alternative might be to put piles of mortar on the floor and don't worry about just trying to get it under the feet. This would support more of the bottom of the tub, and help prevent it from flexing (the big problem for both sound, and eventual stress cracks from the flexing). The mortar should be fine to continue in 24-hours...in fact, probably fine overnight. Won't hurt to leave it longer, just not needed. You want plastic on the floor, too, so that the wooden subfloor doesn't suck too much moisture out of the mix, causing a weak mix.

 

[Sponsor]

 

[Freddie]

Thx Jadnashua. Yeah wasn't clear about where I was going to do it. Over the area of the feet not just the feet them selves to make it easier to plop down. That was my original plan.
The legs are about 3.5 to 3.75" long so that would mean a pile of around 4" of mortar over about 6 sq. ft. if I was going to use the mortar to support the tub as well. That's a lot of mortar weight wise to add to the floor. My main concern is leveling and not supporting the tub given that the manufacturer does not recommend any mortar support and the fact that there is a 3/8" board (looks to be plywood and not particle board) supported by these 5 legs. I know the additional mortar should not hurt unless the additional weight causes problems over the long term.

Do you agree?

 

[Terry]

Homes are built to carry 300 pound cast iron tubs. Your fiberglass tub weighs less than 100 lbs.
The weight of a bit of mortar won't be an issue.
If you have a flat and level floor, you can just drop it in. Often in older homes that's not the case.
If you use mortar, it has to be dropped on it fairly quick. It's sets up fast.
I like to use piles that squish and form to the tub. It's impossible to place mortar at the right height otherwise.