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Help with drop in soaking tub

Posted by Castay2250 (My Page) on
Wed, Sep 11, 13 at 8:36

We are building a new house and we have two bathrooms that are framed at 60 inches. We just bought 2 60 inch drop in soaking tubs. Is the framer going to be able to build box for this to drop into? Will the framer have to take down walls? We are confused. Thanks for your help!

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RE: Help with drop in soaking tub

First question is, are these tub showers? If so, then a drop in tub is the wrong item to have purchased. You need an alcove tub with an integral tile flange. If this is to be a tub only, then the alcove will accept the tubs, but you will have no room for any type of ledger reveal around them. You will have the sides of the tub flow into the walls with your wall cladding.

Drop in tub in alcove. NO shower.

Tub with tile flange for tub/shower situation.

RE: Help with drop in soaking tub

There are usually installation instructions that can be found for the tub on the manufacturer's website. The instructions will include dimensioned drawings from the bottom of the tub's feet to the underside of the tub's rim.

So take the dimensions and installation instructions from the website.

You need to know if the tub will just sit on the subfloor, or if it is to be set into a mortar bed. Just sitting on the subfloor will really define the height of the tub deck, whereas setting it into a mortar bed offers you some flexibility due to the thickness of the mortar bed.

Decide what type of decking material you will use for the tub deck. You need to know the thickness of the material. You also need to know the thicknesses of the materials that make up the substrate for the decking material. Will it simply be a slab of stone set on plywood? Or will it be tile over cement board over plywood?

You work backwards to establish the height of the framed deck.

If you have all that ahead of time yes, the framers can frame the tub deck. If not, they can simply frame the end walls of the alcove and the actual tub deck can be framed in later.

Here's an example where the walls were all framed and the tub deck was added later. In this photo the framing of the tub deck is simply floating in the alcove, it's not secured to the walls. It's simply sitting atop four 2x4 legs. Once the proper overall elevations were established, the final legs were cut, installed, and everything was secured together.

Another shot with variations within:

Here's something I drew up for someone years ago. It shows some of the the rough elements that go into determining the proper elevation for a drop-in tub. Your specific installation may differ, but the overall idea is the same.

Let's say the tub is dimensioned at 19" from the bottom of the tub's rim to the bottom of the tub itself. And the installation instructions recommend setting the tub in a 1" thick (finished thickness) bed of mortar. Add 19" to 1" and you get 20". So you want the finished surface of the tub deck, in this case tile, to be 20" above the platform (or subfloor) that the tub will sit upon.

The tile is 3/8" thick. The cement board 1/2". The plywood 3/4". You have two layers of thinset, one between the ply and cement board, and one between the cement board and the tile, Each are 1/8" thick. Add it all up and you get 1-7/8".

20" minus 1-7/8" is 18-1/8".

So in this case I'd want the framing for the tub deck walls to be 18-1/8" tall. Add the 3/4" ply on top. Then cement board and tile. Then I'd put about a 1-1/2" to 2" thick bed of mortar down, then drop the tub in place. Smoosh the tub down until the underside of the rim just contacts the tile, that should compress the mortar bed to the desired 1" height.

Let the mortar set up a bit, then you can remove any excessive mortar squeeze out if there is any.

Caulk where the tub rim sits on the tile to prevent water splash out from getting under the rim.

There you go.

With all drop-in tubs, you want the weight of the tub to be supported by the subfloor, you don't want the weight of the tub supported by the tub's rim.

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