Hi and thanks again for all the help from you guys. I'm intalling a standard 5' bath tub (American Standard Princeton model), and the plywood subfloor is not level. It's off about 3/8" over the total 5' run, with the low side being where the drain is going.

The way I see it I have two options: 1) install the wall stringer level, then shim the outside of the tub under the skirt so it sits level, or 2) install the stringer parallel to the floor and let the tub slope forward 3/8".

I'm concerned that if I try to level it by shimming the skirt, I may have problems down the road if the shims either move or deteriorate. On the other hand, if the tub's not level it's going to look askey when I tile around the inside walls.

The install directions say to install directly on plywood subfloor and not to use and leveling compounds under the tub. I called the customer support hotline and their only answer was that the floor must be level, and to not install the tub if the floor isn't level. It's not possible for me to level the plywood subfloor.

How should I handle this?

Do you have access to the floor joists under the planned tub location?

>called the customer support hotline and their only answer was that the floor must be level, and to not install the tub if the floor isn't level. <
well, that let's out about 90% of remodel jobs in older homes.
check for level in both directions. (the 5ft and the 32inch.) determine the highest spot. set the top of the leveling board at that height and then nail it to the 2x4's level. set the tub on that board and shim as needed to make it firm. the only time i have ever seen a tub come out of level was not from the shims rotting but from the subfloor rotting from a leak.
3/8" over 5 ft is not that far out. a full cedar shingle is 3/8" thick.

The plaster/mortar should be supporting most of the weight, so the shimming woun't be taking a substantial load anyway. If you have access to the joists and have the time, you can remove the subfloor and sister in level joists, and replace the subfloor, fastening to the level joists.

3/8" doesn't sound like much, but it's enough to make the tile job more difficult. But I'm one of those who are blessed/cursed with a critical eye for plumb level and square.

I do have access to the joists under the tub, but not under the entire bathroom.

Packy, that was the amazing thing! I would say 90% is low....thanks for the info, I'll pick up some cedar shingles to shim with. I've already established the high point, just wasn't sure about the shimming.

Do you have to shim the entire length of the skirt? Or just every x inches?

i was trained at the boston navy yard in the 60's. no such thing as using a level on a boat. sometimes had a 5 or 6 degree port or starboard list.
funny story.. the USS Boston had a pool table in it. very interesting games played on it. especially during a storm.

Even without full access...or even any access, if you realy want the floor level you can strip off all the subfloor and level the joists in the entire room....as always, anything can be done, all it takes is time and money. If you level the whole floor it'll remove the problem you'll have with that shimmed edge when you go to finish the floor. If you're going to have a thick mortar bed tile job, or are thinsetting a relatively thick floor tile, it'll cover that shim job on the low side (most larger floor tiles are 3/8" thick), but if you'll be using vinyl flooring or (ech) carpeting, it's a different story.

"the USS Boston had a pool table in it. very interesting games played on it. especially during a storm"


Did anyone ever win before the break shot?

"the USS Boston had a pool table in it. very interesting games played on it. especially during a storm."

Like "all the balls... corner pocket?"

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the one on the end is the important shim. a couple towards the center will be enough. put some glue around and very gently tap them in. cut of any excess shingle with a utility knife.
just don't ask to borrow my utility knife. it won't cut warm butter..

Craig, I hear what you're saying, but I think that would be overkill to fix a 3/8 problem. I'm confused when you say the mortar will be carrying the bulk of the weight, not the shims. The tub intall directions say not to use any mortar or any thinset under the tub. The floor is getting tiled with 3/8" thick marble that will sit over 1/4" Hardibacker board. I think the unlevel situation will be less noticable to the eye where the floor meets the skirt instead of the in the wall tile.

I know hwt you mean about a critical eye, I am the same way.

Packy, I'll bet more than one bet was won/lost on a surprise from that pool table!!!

Don, I agree completely that it's a lot of work for small reward...hence my 'all it takes is time and money' comment. Everyone's got their criteria for 'acceptable', and I'm pointing out a way to get it if that's what you want/need.

Leveling the floor now is actually a relatively fast and very easy job. It sounds horrific, but you can demo the floor in an hour, and have the whole job done in a day or less. Again, all depends on priorities. As a contractor I wouldn't do it unless it was specifically requested, but as a DIY'er I might have the time to put in that extra day.

Craig, I just replaced a big section of the subfloor that was under the old tub that had some delamination issues from past leaks...house was built in 1973. My big issue is that half of this second floor bath is above the garage where I have already taken out part of ceiling for drain work, etc., but the other half sits above the den that I just remodeled with plasma tv, oak crown molding, etc. The pitch in the bathroom floor runs across the joists, not with them, so I'd need to sister every joist along its length, gradually building them up until the last one is 3/8" higher.

I had a similar issue with the shower pan in our front bath. The floor under it sloped back to front. I shimmed the pan level along it's edges, then used a good quantity of sand mix under the pan. I seated it in the mix and let it set up, tied in the perimeter - good so far after 5 years. The floor under the new fiberglass tub in the back bath is level and I used mix under that anyway.

Unless you are prepared to shim the entire bottom of the tub so it rests entirely on shims, you have no choice except to install it "crooked".

Unless that tub has no support members under it, and it has been some time since I have installed on of those, you should not just shim the apron.

Don you don't have to touch the remodeled ceiling. If you remove the bath subfloor, you have access to the joists. You don't have to sister in full-height joists, just 2x6 or even 2x4 is fine. You simply glue and bolt or lag them to either side of the existing joists. Use a board set to level at each end and pull the joists up to it and secure them. It's easier to do than describe. If you've got plumbing or other obstructions you can notch the sisters without fear of a structural problem. The existing joists take the structural load, and the sisters only support the floor and tub loads.

Craig, thanks for the tip! First thing I need to do is add that clean out port in the drain and replace a tee with a wye...

Love the search function...

I have the same problem Don has/had, even installing the same tub (Americast Princeton). Only difference is my floor is about 1" out of level over 5'!?!?! Oh, and my stingers run parallel to the tub.

I'm curious though, what happens if you install the support stringer parallel to the floor, hence installing the tub 'un-level'? It slopes to the drain end, so it's not like the water isn't going to drain.

Is it just an asthetic issue when it comes to tiling the surround?

Is installing the tub un-level likely to void the warranty?

I can pull up my subfloor, add sister joists, or even rip long shims to intall on top of existing joists, but then my subfloor will be even with the hardwood in the hallway...and I still have 1/4" hardiboard and 1/4" tile to lay...

Could I split the difference, shim 1/2" and have it be 1/2" out of level?

Thanks in advance...

Marty