Bathroom subfloor question

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Diysun

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Hello all,

First time poster who is doing a remodel of my bathroom with Schluter kekerdiboards for the tub surround, and marble tiles on the tub area walls and on the floor.

I originally never intended to tear up the floor, and thought about simply tiling over tile. Folks changed my mind due to some obvious water damage in certain places, and so we removed most of the floor to the joists.

We, however, left the original pink cast iron tub in place (and the flooring underneath) as the original plan was to reglaze the tub (10 yr warranty).

The plan now is to run the new subfloor (double layer plywood) flush and tight to the edge of the tub, and caulk or even use a thin strip of Kerri band to seal the very small gap between flooring.

My questions:

1) would the above plan work? I am concerned that any gap between flooring and the tub, even if we tried to seal it, could allowater to seep through.

2) would the existing flooring underneath to tub remain stable? I know this is a hard q to answer, as the tub currently has much of its weight supported by a ledger board, with the rear two fit actually not resting on the floor! The two front feet are resting on the floor, and it's perfectly level after I shimmed one of the feet (there was some wobble in the tub we noticed after removing the walls).

Thanks all! We don't mind demoing the tub and redoing the entire floor if that's what it takes. But with two little kids we are on a tight schedule to get this bathroom operational again before school starts!

Christian
 

Jadnashua

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Many people do not seal the seam between the tub and the floor and have no problems, but I guess it might depend somewhat on what type of shield you use - a glass door, or a curtain. If you're not going to waterproof the floor, sealing that joint may not buy you much, but if you're planning on using say Ditra on the floor, you could and maintain a watertight seal with the entire rest of the floor if you use Kerdiband on the seams and at the room edges. While two layers of ply is maybe ideal, lots of installs are successful with only one unless you're using a stone tile, where two is required.

I'm not a particular fan of refinishing tubs. You might be lucky, but the cost of a new one isn't often huge relative to the whole bathroom remodeling process. You'll want to address the tub filler valve, and update it to the latest requirements, if it's not one meeting the anti-scald requirements, especially if you have young children that would be using that bathroom.

A good place to discuss tiling things is www.johnbridge.com where that's about the only thing they deal with. This site is great for plumbing issues, and other remodeling, but has few that are versed in industry standard tiling. There are lots of misconceptions and false ideas of how to tile things, but they are good at maintaining things at industry standards.
 

Diysun

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Many people do not seal the seam between the tub and the floor and have no problems, but I guess it might depend somewhat on what type of shield you use - a glass door, or a curtain. If you're not going to waterproof the floor, sealing that joint may not buy you much, but if you're planning on using say Ditra on the floor, you could and maintain a watertight seal with the entire rest of the floor if you use Kerdiband on the seams and at the room edges. While two layers of ply is maybe ideal, lots of installs are successful with only one unless you're using a stone tile, where two is required.

I'm not a particular fan of refinishing tubs. You might be lucky, but the cost of a new one isn't often huge relative to the whole bathroom remodeling process. You'll want to address the tub filler valve, and update it to the latest requirements, if it's not one meeting the anti-scald requirements, especially if you have young children that would be using that bathroom.

A good place to discuss tiling things is www.johnbridge.com where that's about the only thing they deal with. This site is great for plumbing issues, and other remodeling, but has few that are versed in industry standard tiling. There are lots of misconceptions and false ideas of how to tile things, but they are good at maintaining things at industry standards.

Thanks! I heeded your advice, and that of others, and gutted the rest last night. Smashing the cast iron tub was probably the easiest and most enjoyable part of the whole remodel! I plan on adding additional support to the floor with blocking and sister joists before adding a new subfloor.

For the subfloor, I am considering using plytanium dryply t&g 3/4 inch plywood for the first layer, with a second layer of bc grade plywood on top (I will have a natural stone tiled floor). Does this sound good?

I also plan to have the tub drain/trap replaced with PVC, which I believe can be done after the floor is in place through the cutout.

Christian
 

Jadnashua

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You have the materials right...now, it's all about execution. There's a very definite right and wrong way to do that. You can find the details in the 'Liberry' at www.johnbridge.com on placement and fasteners.
 
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I'm in the middle of a remodel now as well and will be adding on to the subfloor. Check out the Ditra installation manual from Schluter. It has some good guidelines about overall thickness, using screws instead of nails, staggering the seams of the second laer, and so on. Real good resource.

https://sccpublic.s3-external-1.ama...8815748186142/DITRA Installation Handbook.pdf

Even if you are not using Ditra, the guidelines on the subfloor prep are good.

Good luck.
 

Diysun

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Thanks all. The subfloor is done! I followed thee Schluter guidelines to a T, so hopefully all will be well.

I have a new "problem" with the apron-less Kohler alcove tub I bought. It was advertised as having an integral tile flange, but upon inspection it is just a flimsy looking tile flange add on kit that was screwed in place. Pretty clear gaps between the tub and flange (and gaps in the corner of the flange itself), and the adhesive seeped through into the inside of the flange in the corners as well (which mag or may not hinder how I position the backer board). I'm adding a pic.

My feeling is I should probably return the tub and buy a different model with a true integral tile flange.
 

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Jadnashua

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My respect for Kohler has decreased over the years. Yes, some of their products are quite good, but some are particularly dogs. Throw in that on some things, they seem to change the design on a whim, and getting parts, should you ever require it, can be quite an adventure. Because of all of the changes, few places other than the factory stock much of theirs in repair parts...makes a weekend repair nearly impossible.

If you otherwise like the tub, a bead of KerdiFix would seal that permanently. Otherwise, you might consider another one. On some, the tiling flange is quite thick, which can make tiling a bit harder trying to keep things in line. There are ways, but it takes a bit more finagling.
 

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Thanks Jad-nashua, your advice has been very helpful.

The tub is ok otherwise (Kohler profile). It's sold as an alcove, but it sure looks like they just added the tile flange to a standard drop in. I bought it since it was an alcove without an apron, and planned to construct my own tiled apron on the front (something I've never done). Both my plumber and gc seem to think the bottom supports are sufficient enough to install without a mortar bed (see pics).

The alternative is to get a standard alcove with integral apron and be done with it (although it would cost a little more for some reason). With thiss option (Kohler archer), I likely would need to set it in a mortar bed.

I'm leaning towards getting a new tub, even if it has an apron, with integral tile flange just to be sure there won't be water issues. Kerdi fix is a good idea too!
 

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Diysun

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Just an update. I decided to return the tub and buy one with a proper integral tile flange. The final straw was noticing that the install document attached to the tub referred to it as a drop-in! Of course the online description and install document referred to it as an alcove with integral tile flange.

Sad thing is I'll probably just replace it with another Kohler (Kohler archer), as there don't seem to be too many sub $1000 options for a 6 ft long alcove tub.
 

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Thought I'd give another update (this is almost turning into a general remodel thread!). The new tub (Kohler archer6 ft) came and it's in great shape. Since the bathroom space is a small 6x9, we thought a 6 ft tub would be a perfect alcove installation. I dry fitted the tub, and it fits perfectly and tightly between the studs! However, the wife feels as though the tub overwhelms the room with its size (72x36), and that a standard 60x32 with a bench may be better.

I'm on the fence myself. The 6 ft tub does look pretty huge, but I'm not sure a 5 ft tub that's only 4 inches less wide will make much of a difference (both the 72 and 60" have the same height).

My other concern with creating a tiled and kerdi -ed bench at the end of a 5 ft tub (to cover the 12" space between the studs), is that this could potentially lead to water issues, leaks down the line. Of course I would waterproof the bench/ledge with kerdi, and provide a slope into the tub, but since this will be used primarily as a shower (and baths for the kids) I'm not sure if this is the best route (or if we just stay with the safer 3wall alcove install).

Thoughts ? Is adding a 12"bench at the end of an alcove tub that will be used mostly as a shower a bad idea?

(Btw, the 5 ft model we would get (archer) doesn't come in a 30 width).

I'm also concerned about being able to shim and put mortar bed under the 72" tub since it's such a tight fit (you have to shimmy into place.

Thanks- Christian
 

Jadnashua

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In a 6' tub, a seat at the end will probably only be used as a shelf since your typical showerhead just won't reach that far, except to maybe wet your feet and lower legs! When I remodeled my similarly sized bathroom, I put a 6' tub at the end. Once you have the tile up and a door, I don't feel it looks out of place, but then, you have to satisfy your partner. Personally, I would have loved to be able to put in a 6.5' tub, but there wasn't room without tearing out a load-bearing wall, which wasn't going to happen! It somewhat depends on how tall you are. It is a real pleasure, for me anyways, to soak. It helps my back, and that's almost impossible in a standard 5' tub. Mine is also an air tub (didn't want to deal with the minimum monthly maintenance of a water jetted design, even if not used).

If I were going to build a bench, I think I'd probably go with KerdiBoard, verses wood, then covering it with a compatible surface that could be covered with Kerdi.
 

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Thanks! I'll probably end up doing whatever the wife prefers, but it's good to hear that a 6 footer could work in a small space. I'm attaching a couple pics of the tub in place. Both my gc and older don't think a mortar bed is necessary, but I may have it done just to be sure.
 

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Another update. Plumber came today and installed the tub with a bit of my help. I really hope it was installed wel and that the plumber knew what he was doing!

Leveling the tub proved to be the biggest issue, as I didn't use SLC on the subfloor. we ended up setting the tub in a mortar bed (thank goodness we did), and leveling 2 of the feet with shims before mailing the flange into the studs (as Kohler requires). The tub now is pretty much perfectly level, which is great.

Unfortunately there is a pretty decent gap between the tub apron and the floor of the tub on one side. I understand people tend to infill that area with mortar or thinset mortar just to provide added stability in case someone sits on the edge or something (as the bulk of the tub is supported by both the shimmed feet and mortar bed).

I may end using self leveling concrete on the rest of the floor just so the tile doesn't look out of whack next to the tub. I may dryfit it first to see if it looks ok without SLC.

Thanks again for all the help!
 

Diysun

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Well, I suppose I have one last question about the tub install. The plumber I used had great reviews, and replaced my drain pipes correctly, but this was my first time using him on a tub install. He was leery of doing a mortar bed on a Kohler archer until I insisted, and so my confidence in his abilities may not be 100 percent. Two issues:

One, I am worried that the plumber sat inside the tub immediately after the install to finish the rough in plumbing. I thought this was a big no no following a mortar bed install? That said, the tub is also resting on its feet (two of the four are shimmed) for support, and I haven't noticed any creaking (feels very solid to me when I get in it). Should I pull the tub and redo since the plumber sat and stood inside it after install?

I was also a little leery of the plumber since, after he left, I noticed that two of the feet needed additional shimming. Just seems like something he should have double checked (I reshimmed).

The second issue is just that the apron is raised about 1/2 to 3/4 of an inch in on one side, since the subfloor in my 1920s house wasn't level. Plumber advised, and my research on the forums archives seems to confirm, that the best way to fix this is to infill with mortar under the apron and it's supports. Sound right?

As to the first issue (sitting in the tub after mortar bed), is this enough of a reason to redo the tub install? It feels very sturdy with no creaks a day later... I just worry that an issue may develop in the future. I don't want to install backerboard and tile yet if this could be a problem.

I kinda think it will be fine since the tub is also supported by its shimmed feet, but wanted to ask you guys what you think before moving forward!!
 
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