[Thomas Kleaton]

Hi! I am installing a new Kohler Bellwether K-837-0 cast iron tub in our 1963 split-level home. I removed the scratched up original Kohler tub. Bathroom is on the second floor, and there are 3/4" boards (some split) where the tub was. The entire bathroom had concrete between the joists where the tile floor was, about 2/3 of the floor.

I broke up the concrete with a rotary hammer and sledgehammer and removed it. I sistered the pointed 2 x 10" floor joists where the concrete was, and covered this with 3/4" plywood subflooring.

The remaining joists in the tub area were already sistered because of the tub weight, but one has a section missing where the drain came through. I am going to re-sister these joists, placing the sister to the tub drain area joist on the other side. Since the wall behind the tub was built on top of the subflooring boards, I will have to use a toe kick saw to cut the boards flush with the joist nearest the rear wall. I will then sister to this joist so I will have a surface to screw edge of new plywood subflooring to.

I plan to add blocking to the joists (leaving clearance for drain) where the tub's feet will sit, as well as using a ledger board (no matter that the instructions tell you not to.)

I am going to cover the remainder of this floor area with 3/4" plywood, and here is my delimma: I am placing 1/2" Durock on the entire floor for tile, except for where the tub sits. Since the rest of the floor will be 1 1/4" (not counting tile height) shouldn't I add 1/2" plywood or some other material on top of the 3/4" subfloor where the tub will be? I plan on tiling all the way up to the tub skirt (leaving gap for caulk bead) and 1/2" Durock around the tub on 3 sides from tub to ceiling for glossy ceramic tile. I am thinking that the tub's feet might be inclined to sink into the plywood. Unless I am mistaken, I am sure the feet need to be leveled before installing ledger board, as well.

Thanks for any replies!

 

[carpdad]

It looks like a regular tub. Tub like it, pros would first lay a layer of cement under the tub. It helps with leveling and distributing the weight. I don't know why ledgers are not used for this. ALL tubs I saw had ledgers. This cement layer is relatively dry mix (holds shape when squeezed into a ball but crumbles - search the videos for what it is) so it doesn't shrink. You'd lay a tar paper first, dry mix and then the tub. Stand the tub first, measure the gap and see how much mix you need. This mix will resist the weight and you may have to stand in it and rock it.


BTW, maybe the manual says don't use the ledge because the tub flange side is less than level? I used americast (plastic tub), I had to install it sloping to outside because if level, water would have pooled around the inside corner. It was very twisted tub. You can sit the tub on the floor, hold it up with sticks and check these things and plan ahead.



Tub also has a over flow tube. This connects with the drain so make sure you leave plenty of room around it. The tub's weight, even full of water, should be distributed by the plywood subfloor and to the joists. As long as your joist spans are in the specs, you don't need whole lot of blocking and sistering.


I don't understand where 1.25" comes from. You have 3/4" ply subfloor. Why another layer of 3/4? Did the floor go down too low? Or your joists inadequate or bouncy? If you want another layer of 3/4, whole bath should get 3/4, then cement board and tile. To protect the lumber, I would redguard the plywood, redquard the cement board, then tile. 2 coats each. Redguard on plywood, imo, is extra protection.

 

[Thomas Kleaton]

1 1/4" is 3/4" plywood with 1/2" Durock cement board on top. I'm sure the tub would crack Durock placed beneath it, otherwise I would just Durock the entire subfloor.

If I don't add another 1/2" of material to tub area, to match height of Durock on rest of subfloor, the tub will sit 1/2" lower than the rest of the subfloor.

 

[carpdad]

Oops. Made more sense yesterday.:smile: I just covered the tub edge with the cement board and tile and didn't think much about losing the tub height. I think old baths with dry mix layer also were done that way. If you want to keep that extra half inch, yes, cement board under the tub too. Also, the old dry mix helped with covering uneven subfloor as well, I read.

 

[huesmann]

Man, good luck humping that mother up the stairs. It's 310 lb. It doesn't need a mortar bed; it appears to have feet that support it—those areas you may wish to provide some extra structural support for.

 

[Thomas Kleaton]

Man, good luck humping that mother up the stairs. It's 310 lb. It doesn't need a mortar bed; it appears to have feet that support it—those areas you may wish to provide some extra structural support for.

Agreed. Me and a guy from where I work had to carry it up 7 steps into the house and it was all I could do to carry my end. Now I'll have to hire the same guy to help me get it 5 more steps up into the bathroom when the floor's ready!

 

[Thomas Kleaton]

Oops. Made more sense yesterday.:smile: I just covered the tub edge with the cement board and tile and didn't think much about losing the tub height. I think old baths with dry mix layer also were done that way. If you want to keep that extra half inch, yes, cement board under the tub too. Also, the old dry mix helped with covering uneven subfloor as well, I read.

Thinking about it, the mortar bed I removed covered about 1 1/2" of the old tub skirt at the floor.

 

[Thomas Kleaton]

Man, good luck humping that mother up the stairs. It's 310 lb. It doesn't need a mortar bed; it appears to have feet that support it—those areas you may wish to provide some extra structural support for.

I plan to block between the floor joists where the tub feet will sit. I read that you can put metal electric junction box covers under the feet to help distribute the load, and to level the tub.

I just wish I had more experience installing a ledger board. I don't like the idea of moving that tub around several times (although I might have to to level it) to get the ledger board screwed to the studs at correct height.

 

[huesmann]

When you say ledger, you mean the cleat along the back wall (this is an alcove tub, right?) that supports the unskirted side of the tub?

 

[Thomas Kleaton]

Yes. The tub has little legs under it, but I've heard you should install a ledger board although Kohler says not to.

 

[ktownskier]

Yes. The tub has little legs under it, but I've heard you should install a ledger board although Kohler says not to.

Ever heard the term: "Read and follow the directions"?

If Kohler who has probably made millions of cast iron tubs is tell you that you don't need a ledger, I would probably agree with them.

Besides, cast-iron isn't all that strong and if you use it to support the tub, it could crack.

 

[Thomas Kleaton]

Ever heard the term: "Read and follow the directions"?

If Kohler who has probably made millions of cast iron tubs is tell you that you don't need a ledger, I would probably agree with them.

Besides, cast-iron isn't all that strong and if you use it to support the tub, it could crack.

No, I wasn't going to use the ledger board to support the tub's weight. That's what the legs are for. The ledger board is to keep the tub's ledge from separating from the wall tile because of expansion and contraction.

 

[huesmann]

The tub has a lip. That should be located behind your lowest row of tiles. You should be using flexible caulk to "tie" the bottom of the tile to the top ledge of the tub. The caulk flex should account for any thermal movement of the tub.

Are you planning to do anything different from this sectional pic?

 

[Thomas Kleaton]

The tub has a lip. That should be located behind your lowest row of tiles. You should be using flexible caulk to "tie" the bottom of the tile to the top ledge of the tub. The caulk flex should account for any thermal movement of the tub.

Are you planning to do anything different from this sectional pic?

That is exactly the way I planned to do it. I am assuming this is the rear wall of the alcove. The cleat pictured is what I meant as a ledger board.

 

[Thomas Kleaton]

Would it hurt to add a layer of 1/4" plywood to the 3/4" subfloor in tub area to raise height of tub to 1/4" below level of surrounding Durock on top of subfloor?

 

[huesmann]

No, I don't think it would hurt. I still don't understand why you need a cleat. In the pic above it's there to support the unskirted side of the tub. I don't know how a "ledger" would keep the ledge from separating from the tile.

 

[Thomas Kleaton]

No, I don't think it would hurt. I still don't understand why you need a cleat. In the pic above it's there to support the unskirted side of the tub. I don't know how a "ledger" would keep the ledge from separating from the tile.

I got my information from Terry Love plumbing forum, Huesmann. Someone said this: "Some, but not all, cast iron tubs have "legs" which fit on the floor, but even with those, a ledger board ensures that the tub ledge will NOT separate from the tile because of expansion and contraction in the wall structure, or settlement of the floor under the legs."

 

[huesmann]

Shrug. If you want it, put it in.

 

[ktownskier]

In the cast iron tubs I have put in, I never put in a cleat. I put in silicone caulk when I set the tub to the wall. So that it was sealed into the location before the tile work was started.

For my non cast iron tubs, I have a kohler one that they want screwed into every joist, kind of like what @huesmann showed. But without the cleat. Although I may use the cleat he showed as well.

 

[Thomas Kleaton]

Shrug. If you want it, put it in.

Not doubting you, huesmann. You know more about this than I do. IF it will be okay without a ledger board, I won't use one. I would install the tub, level it under the feet with metal shims, install 1/2" durock on walls, tile it, and then caulk between tub and tile like in the picture you put up. Did I miss any steps?