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Thread: How to get cast iron tub into alcove and can it sit on 3/4" plywood?

  1. #1
    DIY Junior Member Gardengal's Avatar
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    Default How to get cast iron tub into alcove and can it sit on 3/4" plywood?

    I have the Kohler Mendota tub sitting in our driveway and we haven't figured out how to get into the 61" alcove.
    Our bathroom is down to the studs. Tub is 60"x32". It's a new cast iron weighing 332 lbs (ish) with 4 stubby feet that all the weight must rest on. 2 questions.
    1) How to get this beast into the alcove? I saw the pictures Terry did with the tub vertical against the plumbing wall, and then having it come down, but I don't get where the person is as it's coming down? Too dangerous to be "under the tub". It's not supposed to have weight on the apron. I don't want to scratch this baby. Also there's no crate. I broke the wrapping to inspect for damages then learned I should've kept it in the crate.

    2) Does it need to have metal under those stubby little feet? Seems like all that weight with water and person would sink in to the 3/4" plywood. The instructions say if it's uneven use metal shims, but nothing about metal underneath in general HELP!

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Assuming your subfloor is decent quality (doesn't have a 'D' face which means voids in one or more plies), the tub should sit okay on it and not require anything else. If your floor is not level, (don't confuse flat with level - the tub must be level!), then the tub has to be leveled, and then you may need shims. An alternative, if it doesn't sit level, is to use some mortar underneath. This would provide the leveling and spread the load. This is more common for fiberglass or acrylic tubs that don't have the rigidity of CI, but it can be used for them as well (but it's only providing leveling and not the support). The ledger board and the feet should keep things in place, but the mortar doesn't hurt.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member Gardengal's Avatar
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    They say that this Mendota tub doesn't need a ledger board. Does that change what you said?

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    Forum Admin, Expert Plumber Terry's Avatar
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    I can assure you that I do not place a cast iron tub on my back at any point.
    The tub is in the alcove, and I stand outside the alcove.
    Once I have the tub in the bathroom, still in the crate, I can install without help. It's a one person job at that point.

    Do the tub feet pierce the plywood?
    Yes.
    After going back and seeing some of the installs without the ledger board, you can see the tubs sinking into the floor. NOT MY INSTALLS.

    There is a good reason to use a ledger board for the installs. And it becomes very apparent ten years later.
    On an older home, with uneven floors, it's very important.
    Have you put a level on your floor to determine whether it's level?

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    DIY Member BillTheEngineer's Avatar
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    On a plywood floor chipping/scratching the finish is tough. On concrete i put down a sheet of masonite or 1/4" ply to protect the tub when getting it in place and then pull the masonite or ply out. I don't use a ledger for support. I do put metal shims under the feet on the tub to 1) level the tub and 2) distribute the load over a larger area so it does not sink into the wood over time. If the feet are over a joist it should be fine. If it's in between two joist the 3/4" ply may/will sag over time, not much but enough to have to re-caulk over time. If you can put support between the joints that will help. After shimming the apron of the tub will be about 1/4" off the floor, don't worry the gap will be hidden by the floor tile. If you are not putting in tile or stone, you may need to build up the floor to hide the gap.

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    Forum Admin, Expert Plumber Terry's Avatar
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    Bill, How well are you doing when the three sides of the alcove don't allow access to the tub?

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    Moderator & Master Plumber hj's Avatar
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    You DO need the ledger board. The tub sets on the ledger and the front apron. The feet are just incidental. You place the tub, on a protective piece of wood or something, on its apron in front of the alcove, then "roll" it back until it drops onto the ledger board. Then remove whatever you used to protect the edge of the apron when you started.
    Licensed residential and commercial plumber

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    DIY Senior Member lifespeed's Avatar
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    Some tubs specifically say only the feet are used for support.

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    Forum Admin, Expert Plumber Terry's Avatar
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    Some tubs specifically say only the feet are used for support.
    There are lot's of things said in the instructions that don't make sense.
    I've seen cast iron tubs years later installed without the ledger board, with the "feet" pushing their way through the plywood. It's a pretty sad thing to happen. I've installed hundreds of cast tubs using the ledger board method, and those hold up the best. It's hard to beat decades of in the field experience. It's why we sometimes reverse the order of instructions written by a tech guy called upon to slap out directions on a product he may have never seen in person. We trial and error a lot of things and pass down what has worked best.
    I'm loving how the desk jockey's are second guessing the longest working plumbers on this forum. HJ and I would love for you to work with us in the trenches.

    Just saying.

  10. #10
    DIY Member BillTheEngineer's Avatar
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    I have to reach through the stud cavity, to get the tub shimmed level. To make life easier I usually take a 2 x 6 and screw it to two of the studs in the short walls and use a pulley or come-along and a couple of nylon straps to lift and lower the tub if I can't easily lift the tub with a prybar to put in the shims. This way I am sure to keep all my fingers. The toughest part for me in getting the tub in the alcove. Usually I put the tub on a hand truck to get it in the house and into the bathroom, then it's just muscling it to get it place.

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