Question about making a mortar bed under a tub

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Zanne

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I'm helping my friend with fixing up his house & he wants to switch from a small shower stall to a shower/tub unit. He wants this American Standard Saver tub https://www.lowes.com/pd/American-Standard-Saver-33-75-in-W-x-60-in-L-Arctic-Acrylic-Rectangular-Right-Hand-Drain/3394192 with it's matching surround.

The instructions say to use a mortar bed underneath (although I'm still waiting to hear from the mfr on how much of a gap there is between the floor & the tub's bottom to know how high it needs to be.

I've seen all sorts of different suggestions and opinions on what to use for the mortar bed, what to put under it, what consistency to make it (some say barely wet, others say wetter, etc), and whether or not to put a plastic barrier between the tub & the mortar bed.

I saw the spray foam suggestion but I've seen how spray foam does longterm & it is not a good idea, IMO. Someone suggested the Sika expanding foam that hardens like concrete, but my concern would be it could expand too much. I've seen some people suggest thinset material for mortar and others suggest "drywall mud".

So, some questions:
1. What sort of mortar is the easiest to work with that would yield the best results? Would drywall mud work?
2. What is the best mixing method?
3. How high does the mortar bed need to be? (mfr recommended two 80lb bags of concrete)
4. Can we use roofing felt under the mortar bed?
5. Should we use some sort of plastic sheet or thin barrier/coating on top of the mortar bed to prevent it from clinging to the tub in case the tub needs to be pulled for a repair?
6. For the drain, if the mfr says not to use putty (to use silicone instead), do we still need caulk if we get a caulkless drain (similar to the EZ-Flow shower drain Frodo showed in another thread)?
7. What parts would we need to do a direct connect drain (with trap below the tub's drain instead of below the overflow)? I know we'd need some sort of 1-1/2" straight piece that is threaded on the inside. I saw one from Westbrass. I know we will need the overflow shoe (or what is that piece called?), gasket, plate, etc. We'll need the pipe to go down from the overflow and a sweep to carry it to a sanitary tee for the drain and then the P-trap. I think there needs to be a tub gasket between the drain and the bottom of the tub and we'll need the part that screws in to the threads from the top.

Any help would be appreciated. Pictures are welcome since they help me visualize better.
 

CT18

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We used to just grab some mortar from the masons and plop it down before we set the tubs and then squish it down with the tub. If you go expanding foam make sure you put some screws or nails around the drywall lip of the tub to keep it from rising up.
 

Zanne

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CT18, we've ruled out expanding foam due to the logistics. There will be an acrylic tub surround & no drywall. He might just put some sort of molding to cover the top flange of the wall set.
There are no masons in this area so I don't even know where the type of mortar used on bricks is purchased (likely one of the big box stores an hour away though).
 

CT18

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You could always just mix up some quikcrete and dump it down and then set the tub. We would just hop in it to spread it out underneath. I am not saying what we did was the correct way, we didnt put much thought into it.
 

Jeff Handy

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Don’t set into any mortar or whatever until it is shimmed or supported by framing to be the correct level all around.

Shims should be fastened so they don’t scoot around.

Obviously you want a mortar mix, not any kind of concrete mix, you don’t want any rocks or big aggregate, just sand and cement and maybe additives for flexibility.

But pros would know better, hopefully some will jump in here.
 

Zanne

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Thanks, Jeff. The plan is to hang the ledgerboard and stringers, set the tub in as a dry test-fit to make sure everything lines up and that it is level, then pull it and do the mortar bed & make sure it is up to the height of the bottom of the tub. I'm still trying to figure out the best mix to use & whether to have it wet & peanutbutter consistency or have it like brown sugar where it is damp but not overly wet like some videos show.
 

Helper Dave

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We use a basic, non-structural mortar. Nothing fancy. It does the trick.

The keys to mixing it are that you're looking for it to be grainy and fairly thick. The peanut butter texture is too wet too support anything. You don't want it clumpy, on the other hand. It needs to be consistent to set correctly.

In a five gallon bucket, start off with just 1 1/2" or so of water, so you don't get dry clumps at the bottom. Add a bit of powder, mix, splash on water as needed, and keep adding mortar, then water until you've got the quantity you need.

And a little water goes a long way with mortar. Even too vigorous a splash can be too much, and throw the balance off.

Took me a bit to get the hang of making it when I started, but hopefully my tips help.
 

Zanne

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Thank you very much, Dave! You lived up to the "Helper" part of your name. I will pass the info along to my friend as he will be mixing the mortar.
 

Zanne

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Hmm.. I've never heard of structolite. I'll have to look it up and see if it's available. Only need to set 1 tub currently.
 

Zanne

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I had to go home & take medicine while my friend finished his bathroom, so I don't know how the mortar bed went. But he got his shower & tub installed. Still needs to trim it out & do some painting around it. I will likely do the painting when I'm feeling better.
newtubinstalled1.jpg
 

frodo

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place a piece of tar paper on a wood floor, nothing on a slab
mix 2- 5 gallon buckets of quikrete about 3 gallons in each bucket
dump the stuff on the floor. place the tub over it and press down and level
making sure you do not leave concrete in the way of the drain
 

Pat the Plumber CIL

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Do not use foam . I go to Lowes and buy " Floor Tile Mortar " which is basically the cheapest thinset out there . I use piles and let them squish until tub / shower base is level . Shim and level first . mark walls where level . set in piles of stiff mortar ( less shrinkage )
 

Zanne

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Dang how many products do they use in the shower.
LOL! There are 5 people who use the shower (not counting the little girl who will be using it when the shutdown ends). But I think most of the stuff is for my friend's fiance. She's got a lot of stuff.
 

frodo

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LOL! There are 5 people who use the shower (not counting the little girl who will be using it when the shutdown ends). But I think most of the stuff is for my friend's fiance. She's got a lot of stuff.
I lived in a condo with 3 other guys and 2 girls
we had a rule. keep your sh stuff in your room, and take it with you to the bathroom

Before ''the rule'' the 2 girls had the counter top full of make up. Glen got mad. tossed everything out the window. all hell broke loose.
After ''the rule'' we had a LOT of room on the counter to take care of bidness
 

havasu

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Exactly why me and the G/F have our own bathrooms. Before this, I reached for my toothbrush, knocked over her mascara, which knocked her toothpaste over, which knocked her perfume bottle over, which knocked her foundation ( ?) over, which knocked her lipstick over,which made her mouthwash fall over, causing her mouthwash cup fall over, which made her 4 lipsticks fall over, which pushed the cotton balls all over the floor while flipping her container of Q tips over, which dumped her hand lotion into the sink............
 

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