Alcove Bath Tub Install - Semi finished walls - Ledger Boards & Mortar?

[RobK68]

Next stage of bathroom renos is installation of a 60"x30" alcove tub. (Tub detail here)
The manufacturer's instructions are poor, so I've learned more from forums like these than the actual instructions. The instructions illustrate the enclosure having ledger strips. The written instructions make no reference of these, but do write that a mortar bed should be used. My questions ....

1) Should I use ledger boards only? Mortar only (piles, not a bed)? Both?
2) The tub has levelling feet according to the instructions, but not sure how. Does that change the advice given for question #1? I have no idea how to get to said levelling legs to use them with three of the walls being inaccessible, with the front having an apron. If there was access to the levelling legs, would they get set in the mortar before adjustment?
3) If I use ledger boards and mortar, what height allowance for the mortar should I give when mounting the ledger boards?
4) Best product for "Mortar piles?"
5) Plastic barrier between mortar and cement board floor and tub base recommended?

 

[Tuttles Revenge]

They have a complete installation instruction sheet. https://www.valleyacrylic.com/cdn/s...tub_Manual_MAR2021.pdf?v=10119190860840221884

The unit must be installed perfectly leveled. Level the unit using our adjustable 2 x 4 legs to the floor under the wooden base or using mortar cement. All the legs must be in contact with the floor. If the 2 x 4 legs does not permit it, it is imperative to add a wood edge to support the bath or the shower. To provide additional support, improve soundproofing and facilitate leveling, it is recommended that a layer of mortar be applied to the base of the bathtub legs, and covered with a 1/16” (2 mm) polyethylene sheet. The layer should be thick enough to facilitate the leveling of the unit without raising it. Once the unit is in position, ensure it is level in both directions for proper draining. Leveling must be done under the wood legs located beneath the unit. Do not level directly behind or under the flange at the front of the unit.

No mention of a ledger, because the entire weight should be born on the base, not the ledge.

I like to set the tub in get it perfectly level, scribe a line so I can just get back to that as I squish it into the mortar.

 

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[Jeff H Young]

I like tuttles instruction. Ive had much debate regarding ledger boards allways use them on press steel , I havent done many fiberglas because those are often tub /shower and the install often done by others. Cast iron tubs Im ok with a ledger or with out if the tub is really set good with mortar solid wide feet then the ledger isnt really needed but I dont see how if everything is done right that support under the long edge (ledger) can hurt a bit more insurance. To me its not about doing the minimum to get an ok job its about taking a half hour longer getting a life long job, no rocking , settling etc. (or call backs) A big part of this is the structure if you have some settle in the floor that ledger board will carry some weight .

 

[RobK68]

Thanks folks,

I'm assuming that since I can't get to the levelling feet within the closed enclosure with the skirt to adjust them (instructions also state "DO NOT build the surrounding structure before receiving your unit. S" - I'm already having to work around the instructions) that the ledger would be required? "If the 2 x 4 legs does not permit it, it is imperative to add a wood edge to support the bath or the shower" - Isn't a "wood edge" a ledger board?

Mortar is only "recommended" ... and only under the legs? "mortar be applied to the base of the bathtub legs", although the illustrations show a layer. Bad instruction ... this reads adding the mortar to the legs, not the floor, if one can access the legs.

I'm feeling that the only true way of levelling, although using the adjustable legs is the manufacturer's recommendation, that a combination of mortar and ledger may be the way to go. The manufacturer seems to rely on the leveling legs and fastening to the studs as being the only support, with added support/noise reduction from a layer (not piles) of mortar. The extra work isn't an issue, but I don't want to do anything that jeopardizes the install. This being the plan, how thick a layer of mortar should I anticipate so that a ledge can be installed at a height that will ensure that the base of the tub is sitting level in the mortar (unless the tub base sits on the floor with the mortar squished out to the sides?

I'm probably overthinking this ...

 

[Tuttles Revenge]

The reason they want you to build the framing after the tub arrives is that they don't have great tolerances on their fiberglass. We usually ask builders to build 1/4-1/2" larger than the tub dimension or leave one wall unfastened to make up the adjustment. If the tub is smaller the gaps are usually split between each side or however the tile installer wants to make their product look good.

Installing a tub is mostly figuring out how to uninstall it and make adjustments the least number of times. That is why I recommend setting it in the space, figuring out where it sets perfect, scribing that line and then just filling in under the tub with mortar. Once that sets up it will never move out of level. Adding a ledger in addition to the mortar allows you to skip the scribed line I suppose and as long as the weight of the tub basin is born on the legs and or mortar there won't be any flex against the ledge... which is the reason you can't install that tub with just a ledger and not support from the base, the ledges are not designed to bear that weight.

I dont know what to say about the legs.. that could be as simple as making some rough gestimation as to how far to adjust then pulling the tub and making smaller adjustments til you have it leveled... making 100% that the legs can't self adjust later.. Locktite or a locknut would be ways to prevent that, but I would imagine they come with locknuts.

 

[Jeff H Young]

its trial and error on the leg adjustment many dont have adjustment but regardless You really dont want those feet in the air at all And I dont want my mortar under the feet