Setting Kohler Archer tub in mortar

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Los Angeles
I'm looking for advice on setting a new tub in mortar. The old tub had a crack in the middle, so I want to make sure that the new one won't have that problem ;-)


The first question is about the opening for the drain. It's too big on the right side. That's great for access, but do you think it needs to be made smaller to properly support the tub?

This is what the tub looks like in place.

I traced the outline of the hole on the bottom of the tub. About 7" in the front hang over the hole. This is the end of the tub where people would get in, but I think that they would normally put their foot down on the other side of the drain, not all the way in the front.


Next questions are about setting it in mortar. I have access from the drain side and from the opposite side. So my plan is to prop those ends up with some wood, high enough to give me space to easily place the mortar underneath - maybe 7 or 8" off the ground.

This old thread answered a lot of questions for me. Putting mortar in mounds makes a lot of sense. I'm not 100% sold on putting it in plastic bags, though. I like the cleanliness and control that this method offers, but it seems like "naked" mortar would spread better and make better contact with the surfaces.

The first question here is how far should the mortar piles extend? Putting them just under the bottom would accomplish the goal of preventing flexing when there is a lot of weight in the tub. But does it make sense to also place mortar around those skirt supports outlined in red to prevent any movement?


Next question is about leveling the tub. It seems like it's very easy to push the tub down too much in some places, over-compressing and squeezing out the mortar. Pulling it back up will then leave a gap. How do you deal with that? Just be careful not to push it down too much? It's probably best to have something that will stop it from going too low. I saw the method with the stringer in the back and shims in the front, but I'm thinking it might be simpler to just cut and glue a shim to each leg to make the tub level. Then I can push it down all the way without the possibility of it going too low.

And last question, is this a good choice for the mortar, and should I mix it according to instructions or add less water to make it more dry?
QUIKRETE Deck Mud 50-lb Concrete Mix

Thanks for your help!


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John Gayewski

In the Trades
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I would have it supported in your blue outline. Yes it looks like some of the floor might need put back around the drain, although I might consider packing pea gravel or clean rock in that hole up to the top, and then covering it with mortar (we use plaster) that way when/if that tub is removed whomever does it, won't need to break up more floor again in the future.
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