Questions on tub mortar setting and ledger board

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Leah F.

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Hello,

We are getting ready to replace our old tub with a new Kohler Bancroft tub and I have gotten a lot of information about mortar support for the tub floor on this site and I am so thankful for this forum. I have some last remaining questions for your folks' opinions:
1 - After demo we see that the sub-floor has a big square cut from it for the drain. Is it necessary to get mortar coverage in that area? (see pic attached from another person's post that looks like my set up).
2 - Also wondering if the Quikrete mortar mix package instructions for water is good enough or if anyone recommends a different thickness?
3 - How soon after laying (or piling) Quickrete is it safe to start stepping in the tub to do the tiling?
4 - Is it worthwhile to fill the tub with water to help settle the tub?
5 - Our tub does not require a ledger board installation, just screwing the tile flange to the wall, but would it hurt to install the board anyway?

LF
 

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Reach4

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Search using the box above for mortar piles. The word "bed" sounds like an even layer, and you do not want that.
 

Jadnashua

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Quikcrete makes lots of different products...a sand mix (4:1 sand:cement) works decent. It will be more like wet beach sand - won't flow, but will squish down as long as you do it in piles. It should hold together if you pick up a handful and squeeze like a snowball, and it should not drip, but should hold together. To help keep the subflooring from sucking moisture out, you can put down a layer of plastic or tar paper which will make the mix stronger. You really want to let it cure at least overnight. A ledger won't hurt if you can find a straight one and can get it level at the desired height.

Unless the hole around the drain is huge, don't worry about it...you need some room to work and get the drain and trap adjusted properly.
 

Leah F.

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Thank you. I have a related question: I have read that the mortar mix might shrink. Do you think that putting plastic down and keeping the mix from being too wet is what prevents the mortar mix from the shrinking problem I have been reading about?

Also, I was considering putting another sheet of plastic on TOP of the mortar--do you think that will make the work more difficult?
 

Jadnashua

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Cement mixed with too much water will shrink. A deck mud is mixed so that it is still dry (more like wet beach sand) and while all of it is wetted, when you squeeze a clump, it should not drip excess water, but should hold together.

It depends on the shape of your tub's bottom whether another sheet of plastic would make things more difficult or not. If the tub has lots of pockets from ribs, it may or may not work well. Deck mud, as opposed to a concrete mix, normally doesn't stick well to the tub, so it can still be removed. The reason for the plastic on the wooden subfloor is to restrict it from sucking moisture out, but it also makes it easier during your next remodel.
 

Leah F.

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Cement mixed with too much water will shrink. A deck mud is mixed so that it is still dry (more like wet beach sand) and while all of it is wetted, when you squeeze a clump, it should not drip excess water, but should hold together.

Thank you Jim.

Now I know how to prevent shrinkage by not getting the mixture too wet, I'm all set--pardon the pun. Ha Ha!
 

Leah F.

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Quikcrete makes lots of different products...a sand mix (4:1 sand:cement) works decent. It will be more like wet beach sand - won't flow, but will squish down as long as you do it in piles. It should hold together if you pick up a handful and squeeze like a snowball, and it should not drip, but should hold together. To help keep the subflooring from sucking moisture out, you can put down a layer of plastic or tar paper which will make the mix stronger. You really want to let it cure at least overnight. A ledger won't hurt if you can find a straight one and can get it level at the desired height.

Unless the hole around the drain is huge, don't worry about it...you need some room to work and get the drain and trap adjusted properly.

Thanks for answering all my questions.
 
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