Bathtub installation -- order of installation (end pony wall, tub, heated floor)?

[jch]

Here is my gutted bathroom. I have a left-hand-drain Kohler Villager cast iron tub (with apron) that I want to install along the far wall (i.e. along the wall that has exposed insulation):



The tub is 60" long and the available space is 78" (with a downward-sloping ceiling).

Questions:
1) Do I install the tub (on a ledger board) *before* building a pony wall along the non-drain end of the tub? Or do I build the short (20" 2x6) pony wall first?

2) I plan on installing a heated tile floor. Because the room has some funny angles (not visible in the picture), I was going to run my own heating cables and then pour Self-Leveling Cement. Do I run the cables and pour the whole floor *before* installing the tub? Or do I put in the tub first and then pour SLC on the remaining area? (The heating cable would only be under the exposed tiles, not the tub). My concern is the joint between the tub & SLC, and the reduction of tub-height -- it's only 14" to start with.

This is my first bathroom reno, so I'd appreciate any tips.

Thanks!
.../j

[Terry]

In this case you could do it either way, either set the tub first or install the pony wall first.

When we install a tub, we put a 2x4 flat; if that is the right height of the concrete pour, and then pour up to that. I don't like setting a heavy tub on concrete if it's that thin. The 2x4 makes a nice resting place for the apron.

Then you can finish tile up to the tub.

http://www.terrylove.com/forums/show...-Cast-Iron-Tub

[jch]

Thanks for the speedy reply Terry!

I'm hoping that the concrete won't need to be that thick (for headroom). I was hoping for more like 1/4 - 3/8" thick SLC if possible. Or am I dreaming?

And does the wooden apron support stick out in front of the apron? Or do you try to install it flush with the front of the apron?

Thanks!

[Terry]

I haven't installed the electric heating mats, but they may go under the tile without doing too much.
If that is the case, just set the tub on the plywood.

You only support at the back wall. One stringer does it.

[jch]

The more I think about it, the more I think that I'd better do the SLC last. I *know* I'd end up dropping something on it while wrestling a cast iron tub around the room...

So how does this sound then:
1) Build 2x6 pony wall along non-drain end of tub
2) Install wooden 1x4(?) along floor where tub apron will sit
3) Install 1x4 or 2x4 ledger along wall (depending on clearance of tub), measuring up from top edge of apron support
4) Skid/rotate tub into place using instructions here: http://www.terrylove.com/forums/show...-Cast-Iron-Tub
5) Install in-floor heating cable
6) Pour SLC to bury cable
7) Install Schluter Ditra anti-fracture membrane on top of SLC with thinset
8) Install floor tiles

Sound good??

[Terry]

You have enough room there that you may be able to just slide the tub in.

But either way, so far, so good. That looks close enough for a plan.

[jch]

Excellent. Thanks!

[jadnashua]

SLC is MUCH easier to get nice and level (with no waves, etc.) if you make it a little thicker than you plan. Also, over a wooden subfloor, you need lath - I'd suggest a plastic lath rather than metal as the metal can mess with the insulation on your heating wires if you step on them before the pour. Depending on the slc chosen, some require 1/2" above the highest point when used over wood...take the longest level you have to determine how level the floor is before calculating how much slc you need. the worst thing is to have too little. Check out www.johnbridge.com and read up on slc use - lots of threads and info in their 'Liberry'. Finally, ensure you get a good coat of the primer for the slc or the whole install will be at risk.

[jch]

Thanks for the tip. I haven't checked out johnbridge lately, so I'll drop by there to refresh my memory.

The floor is currently within 1/8" of being flat and level. I pulled up the subfloor and planed down the top of the joists in line with a laser.

The only reason for me using SLC is to bury the heating wire. Perhaps it'd be worth spending the extra for heating mats and using thinset instead??

[jadnashua]

Either will work, but slc over top does make it nice and flat while embedding the heating elements well, optimizing the heat transfer and providing a nice flat surface to tile on.

[johnfrwhipple]

There are many heating mats that can be used for sure but I'm more of a fan of heating cables.

The Mats offer up a little extra speed in installation but a cable system offers a direct bond from the top of the levelling compound to the subfloor and does not rely on the manufacture's seaming process of the two sheets. With a mat system you need to work the thin-set into the fleece very well and this can be hard to do well without over watering the thin-set and weakening that product.

Once the cable heat is installed you might consider a product like Schluter's 'Ditra', Nobel Company's 'Nobel TS' or Mapei's 'Crack and Sound Membrane' over your levelling pour. Remember if you use the Ditra product you will strictly reduce the amount of setting materials available to you. Here in Vancouver the crews I'm working with have been using lots of the Mapei product and many of the setters online have been using Nobel TS. Mostly because they can use the same thin-set to set above and below the membrane.

If this is your first bathroom renovation you might further consider using a liquid membrane for all these steps including the bathtubs walls. Look at products from Mapei (AquaDefense) and Laticrete (Hydro Ban). Both offer up crack surpression and waterproofing. Much easier to work with than Kerdi.

Good Luck.

[hj]

Installing the bathtub will be MUCH easier if it is done BEFORE the pony wall is constructed.

[jch]

There are many heating mats that can be used for sure but I'm more of a fan of heating cables.

I'm looking at using the NuHeat Solo/220 wall controller (because it seems easy to program without digging out a manual each time). Is there a type of compatible heating cable you'd recommend? I was thinking of using TrueComfort because of the floor attachments and easy availability...

Once the cable heat is installed you might consider a product like Schluter's 'Ditra', Nobel Company's 'Nobel TS' or Mapei's 'Crack and Sound Membrane' over your levelling pour. Remember if you use the Ditra product you will strictly reduce the amount of setting materials available to you. Here in Vancouver the crews I'm working with have been using lots of the Mapei product and many of the setters online have been using Nobel TS. Mostly because they can use the same thin-set to set above and below the membrane.

The original plan was to lay down:
3/4" ply with no underlay
SLC primer
Heating cables
SLC primer
SLC
Ditra
Porcelain Tiles

Do I need underlayment if I use the SLC primer directly on the plywood? Or would underlayment mean that I could do without the plastic lathe in the SLC??

If this is your first bathroom renovation you might further consider using a liquid membrane for all these steps including the bathtubs walls. Look at products from Mapei (AquaDefense) and Laticrete (Hydro Ban). Both offer up crack surpression and waterproofing. Much easier to work with than Kerdi.

Interesting. My neighbour's son (a tile setter for 25+ years) swears by RedGuard. Maybe it's the heavy Mike Holmes/Schluter PR, but I'm having a hard time trusting that a rubbery paint-on membrane won't dry out/crack over the years... (Actually, that I'd be able to install it so that it wouldn't crack..)

I've already bought a Schluter shower kit (pan, curb, drain, Kerdi) to use in the *other* bathroom reno in the house so I'm gonna have to learn how to use it/curse it at some point :-) I'll definitely consider using a paint-on membrane on the first one.

Thanks!

[jch]

Installing the bathtub will be MUCH easier if it is done BEFORE the pony wall is constructed.

Would you recommend connecting the drains before building the pony wall? I have access from the bathroom underneath (it's all bare joists baby!).

[jadnashua]

It's always easiest to install the drains when you have easy access. It can be done either way, but afterwards requires more skill.

Ditra has a minimum tile size (2"). This is to ensure that enough of the tile is supported by pillars of thinset around the waffles so it won't cock if stepped on with a high load point source. Other than that, it's pretty easy to use. Some thinset manufacturers sell a decent unmodified and you can mix it either with water (and maintain the unmodified characteristics), or mix it with their addative, and that makes it a modified thinset (rather than buying a modified at the plant that you then mix only with water). Done this way, you don't need two different thinsets, just depends on how you mix it up. Because of the waffles in Ditra, the amount of actual thinset used may end up less than with a plain membrane - painted on or embedded.

The critical thing with Kerdi is mixing the thinset properly and using a quality product. Second, getting it up before the thinset skins over. embedding is really pretty easy once you get the hang of it if the thinset is done right. If you can find it, DitraSet is a really nice, creamy thinset made for Schluter. The key to proper thinset mixing is the right mix, the right paddle, and mixing it long enough. Using a timer helps. most people don't mix their thinset per the manufacturer's instructions. The difference in texture can be quite dramatic - those extra minute(s) really make a difference. Some people compensate by adding extra water. this is often unnecessary, and weakens the thinset, if the proper mixing is done.

A manufacturer's rep told this story to us in a class. they had a pro complain about the texture of one of their thinsets. The pro watched as the guy mixed up a batch. Knowing it would be hard to change the guy's mind, they said let us research it. They came back a few weeks later and told him they had some new stuff for him to try. The guy mixed it up the way he usually did, and the tech said...keep mixing. this went on for a couple of iterations. Then, after the manufacturer's mixing time had been used, he told the guy that's good. The guy then commented that the stuff was MUCH better. Then, the rep told him that it was exactly the same thinset...just that it had been mixed per instructions.

The gotcha with paint on membranes is achieving the required thickness. Most people have a difficult time actually getting it thick enough, and pinholes are a potential problem as well. Get it too thick and you've spent a bunch more in materials and time than needed. Too thin, and it won't do the proper job.