semi-sunken tub surround [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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03-19-2006, 05:28 PM
Hi I want to put an acrylic tub - the ZUMA COLLECTION C6632 - into a bathroom in a one story tract house. Raised foundation with continuous footing around the perimeter. The house is currently gutted. Tub would be installed on an outside wall. Walls studs are 2x4 and we are finishing with tile.

Husband is telling me not easy to do a sunken tub surround because we would have to excavate the foundation in order to build the tub surround. (he's skinning the cat one way, by building the surround where the tub is going to be) Also he says we would have to pour a foundation pad in order to support the weight of the tub.

My questions are

#1 could we build the tub surround away from the site, and then cut a hole in the subfloor a bit larger than the surround and then lower the surround into the hole?

#2 what sort of prep would be required in the way of foundation/support underneath where the tub surround is going? (its just dirt under there right now).

#3 would you build the tub surround with plywood around the sides of the base so that the mortar base would stay in place?

thanks so much in advance for the help!

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03-19-2006, 06:10 PM
I need a few answers before I can say a whole lot.

Have you got a link or picture that shows the tub? What are you calling the "surround", the deck or walls around the tub?

The wood subfloor would probably have to be beefed up to support a tub, not sure if a concrete pad is needed. Normally a tub deck is built in place.

03-19-2006, 06:27 PM
here's the tub:

The tub surround? I meant the frame that you have to build in order to have a drop-in tub. The frame? Is that what its called? The frame consists of both the walls around the outside of the tub and the deck, right?

You would build a frame into which the tub is lowered and the lip of the tub extends over the finished surface of the frame, tile in this case. But all of the acrylic whirlpool tubs say that they must be supported from the bottom, usually set in a mortar base. Also, they say that the weight of the tub should not be supported by the rim/lip of the tub.

I don't want the subfloor to support the tub, I want to cut a tub-frame-sized hole in the subfloor so that the tub (and its frame) can be sunken below the subfloor. And that needs to be supported from below. Below the subfloor is about 18" of air and then dirt.

I think it would be okay (thought not easy) to build the tub deck in place, after we cut a hole in the subfloor; so I guess what I am asking is what we should put under the tub deck.

03-19-2006, 06:38 PM
Sorry to have more questions than you. :yeah: If you drop the tub down 18 inches, won't the tub be set on the floor and not have a deck at all? Or do you want it dropped only part way, maybe 12 inches and have a short deck?

03-19-2006, 06:46 PM
It is normal to have a mud bed applied over the wood floor to support the tub. Addional framing strength may be needed. I'm not sure but it might need a pad poured just for the tub although I wouldn't want the pad the settle over time leaving the tub weight on the lip. I'll ping CX, he might can help out better than I can.

03-19-2006, 07:04 PM
Welcome, KiKi. If that's not your first name, please upply one. :)

I'm a little confused like my friend, Davy.

I see that your tub is about 20" deep, and your crawl-space is about 18" deep. And your floor is constructed of sawn wood joists of some sufficient size, supported on one end by an exterior wall adjacent to which you want to install this tub, and at the other end by........?

And you want to pour a concrete foundation below where you plan to install the tub so the bottom of the tub sits about - (fills in dimension) - below the current finished floor. Right?

Then you want a surround which you can tile to enclose the remainder of the tub that is above the finished floor. Right?

What part of the country are y'all in? How deep are the footings for the perimeter walls of the house?

Are we getting close to the right questions?

03-19-2006, 07:06 PM
ask away!! I appreciate the help and you need all the information in order to help, yes?

Yes, I want to sink the tub partially, around 12" total from the top of the rim of the tub to the finished floor. Finished floor will be 1" above sub floor.

03-19-2006, 07:29 PM
ok, CX, yep, the right questions are coming from the both of ya! :nod:

The sub floor is of 1" TnG cedar planks and is supported by 4x8 beams sitting on top of a sill plate on top of the foundation at the perimeter, but supported by 4x4 posts in concrete pilons across the interior of the house. Husband says some rooms have just one floor "beam" running the length of the room, supported by the pilons along the way. Not the usual stick construction with 2x6 floor joists every 24" o.c. We hadn't seen anything like it before. I wish I had some as built drawings but alas, not. Tract home built in 1940 Southern Cali: Mar Vista to be exact.

The foundation footings around the perimeter of the house are 3' deep(probably - if the house was built to code in 1940).

And, yep, I want to pour a concrete foundation below where we are installing the tub so that the top of the tub is about 12" above the finished floor of the bathroom. and then, yep, want to have a surround that we can tile to cover the remainder of the tub.

Husband says have to cut the foundation in order to build the frame for the tub, and also to dig for the footing for underneath the tub. I think we could maybe lower the frame into the space after we build it.


03-19-2006, 08:07 PM
I don't really see anything wrong with what you want to do although Cx would know of possible problems before I would. You're going to alot of trouble but nothing wrong with that. :nod:

03-19-2006, 10:29 PM
Well, we've found that to be a very common type of construction in your part of the country, Niki. I'd expect you to have piers spaced no more than about five or six feet apart (sometimes less) under there and the 4x8 beams to be spaced on 48-inch centers. That compute?

I'm also gonna guess that the subfloor boards are closer to 1 1/2" thick than 1".

And I'm further gonna guess that in southern California where there is no frost line your foundations aren't required to be three feet into the ground. But I'm not really familiar with y'all's codes.

I trust your location also means you won't have a big problem with freeze-proofing the tub and equipment under there and all. And I trust further that you've already dealt with the drain and water supply for that installation.

I agree that you can dig pier holes and pour a big ol' concrete pad for that tub, but since you're only fixin' to drop it about eight inches, you might wanna consider just hanging a dropped subfloor from the bottom of the existing beam structure. It would depend upon the direction of the beams and the location of the tub, of course, but that might save a lot of work. 'Course, if you're needin' to be cuttin' into one of those beams and moving piers and such anyway, that may not help you at all.

As for the surround, I think you're overthinking that part. Once you've done all the structural work for dropping the tub, I'd think you could just replace the subfloor and then build you a framework for the tub surround and deck right on the floor. But maybe I'm missing something?

My opinion; worth price charged.

03-20-2006, 11:48 AM

Are you hanging around underneath my house? You got it spot on. And initially they thought we'd have to cut the beam and move the posts and I said that's a lot of work lets not do that.

And, yep, Davy going to a lot of trouble. course I saw a picture in a magazine and the rest is history.

So, hang a dropped subfloor from the existing beam structure? Those beams are good to support the weight of the tub, huh, since they got a whole house worth of weight on them right now. Sounds good. I'll float that to the boys today and see what they say....wish me luck.

Thanks to you both!! I'll post updates..... :nod:

03-20-2006, 11:58 AM
Well, it'll take some on-site evaluation, Kiki, but you're only dealing with about 1200 pounds, maybe 1400 worst case, so even with only four attachments you only need 300 to 350 pounds each. If you can attach close to the support piers (or even on the support piers), that should be no trouble at all.

My opinion; worth price charged.