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Unread 01-02-2020, 06:33 PM   #1
speculative mason
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Tub to shower project

Ello,

I am starting a tub to shower project tomorrow.
It is a fiberglass tub on a slab.
I am expecting a box around the shower drain floor that has to be concreted?
I understand that a sandy mix is used for floors because it is more dimensionally
stable.
Will i have to wait a long time to do the pre-slope with deck mud after i
concrete patch?
Can i use standard concrete for the patch and do i need any type of rebar or mesh?

Also, i read on The Floor Elf advice blog that there should be 1 to 1 1/2 inches
of deck mud below drain plate.
I was not sure if this was pre-slope and shower floor together or just the shower floor.
This is for someone with some mobility issues and i am trying to keep it as low
as possible.
The drain is offset with about 4 and a half feet to one side of it requiring 1 and 1/8 inch slope as i understand it.
If the preslope was 3/4 thick at the drain plus the 1 to 1 1/2 inch floor plus
the 1 1/8 inch slope i am at about 3 inches above the rest of the floor and that's before the curb.
I guess i am wondering what the minimum thickness you can make deck mud;
i would like to have the pre-slope taper to zero or the thickness of the bottom
flange of the drain if possible and use the thinnest possible deck mud floor.

Is it a crazy idea to carve out a preslope in the slab?
The only tool i have for that that i can think of is a 4 inch angle grinder with
diamond wheels.

Thanks for any help.
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Unread 01-02-2020, 07:03 PM   #2
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Welcome back, George.

If your intent is to keep your new shower floor and curb as low as possible, you're taking the wrong approach in using a traditional mud/liner/mud type of shower receptor. If you switch to a bonded waterproofing membrane type of waterproofing, your shower floor consists of a single sloped mud bed with the membrane over that and tile bonded to the membrane. You still need a minimum thickness of your mud at the drain to be 3/4s of an inch, or, if your slab is actually flat and near perfectly level you could use one of the foam shower trays and reduce that height a bit more.

First thing I would recommend is that you move the drain to the center of your shower footprint. That will also allow you to lower the perimeter height a little more.

When I patch any holes in concrete SOG I add rebar to the extent feasible, drilled into the sides of the concrete cut. I would wait only until the concrete patch was firm enough to work over before placing a deck mud bed.

Trying to cut into a SOG to lower a shower floor is a risky business. If you're sure, really sure, that your foundation was not poured with post tension cables as opposed to steel reinforcement, you could try that I suppose. Same caution would apply when cutting a trench to move the drain, but you can actually work around the cables in that instance.

Another option would be to raise the rest of the bathroom floor using deck mud to make a barrier-free shower entry with no curb at all.

My opinion; worth price charged.
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Unread 01-03-2020, 12:06 AM   #3
speculative mason
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Thank you CX,

That is a relief about mudding on the concrete, i have read some
recommendations of 3 weeks.
This is the only bathroom in the house so time is an issue.
I told the 'customer' one week before i started researching the job and i am
seeing a lot of wait a minimum of 24 hrs. steps.
I briefly looked into that membrane system but cost is also an issue and
it looks like it would be 3-4 hundred dollars more than Redgard walls and pan liner.

For the drain trench and patch should i put gravel under the pipe? Under and over and all around the pipe?
And should i put plastic sheeting under the concrete?

If do try and center the drain and i hit some steel i should know it and be able to stop before cutting a cable?
Then i can chisel around it and tell if it's rebar or a cable?


When you drill holes for the rebar are you able to get a single piece into both sides
of the trench? Maybe a separate piece on each side and tie them together?
A bonding agent on the old concrete?


Oh, and the minimum 3/4 of an inch mud thickness, is that for each layer (pre-slope and the floor on top of the liner) or can the sum of them be 3/4?

Thanks Again
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Unread 01-03-2020, 10:38 AM   #4
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I think you're exaggerating the cost difference between the two shower construction methods, George, but even if not, a few hundred dollars in the cost of a bathroom remodel is usually not a large upgrade. And considering that it allows you to actually do what the customer wants, makes it no upgrade at all in the grand scheme of things.

I fill all concrete patch areas with a compactable fill to the bottom of the existing concrete SOG, then fill the remainder with concrete.

Rarely, if ever, possible to drill a single re-bar into both sides of a patch. Doweling into each side and tying them together is generally the way to go. And I repair the vapor barrier material to the extent feasible. Like so:

Name:  Vapor Barrier Patch.jpg
Views: 129
Size:  61.9 KB

And yes, a bonding agent, usually a slurry of pure Portland cement or thinset mortar for me.

You first determine whether you have a post-tensioned slab before you start any cutting. If you do, you must be very careful to locate the cables in the repair area before you start any cutting with any machine. If you have a steel reinforced slab, you get a lot more aggressive and work around or through whatever re-bar you encounter.

the minimum 3/4" of deck mud at the drain is for the pre-slope of a traditional shower receptor. Then the waterproof liner and and additional minimum of 1 1/2" of deck mud for the final mud bed. If you use a direct bonded waterproofing membrane for your receptor, you require only the first 3/4" thickness at the drain up to the height required for a minimum rise of 1/4" per foot to the farthest corner of the shower. You can get by with less slope if you convince your local code compliance inspector that you can make the shower comply with Accessibility standards.

My opinion; worth price charged.
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Unread 01-04-2020, 08:23 AM   #5
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Thanks so much.

I feel pretty overwhelmed and it is comforting to get some experienced advice.

I did decide to move the drain and am taking it real slow in case there are
cables.

The fill is some type of black sand, it looks like ground obsidian or Arkansas
stone, real shiny.
Does not seem like tamping it has any effect, remains real loose.


The cost difference i figured included doing the walls with that orange membrane and
also it looked like a special drain was required.

Could i Redgard the pan and just do the 3/4" thick preslope?
Maybe Redagrad the bottom plates and the studs a little.

My problem now that there is no turning back is the drain.
I Googled where to do the transition from 2" to 1-1/2" and there is a near
unanimous consensus to not do that at all.
The 1/ 1/2 pipe disappears under the wall and i can't tell where it joins a larger
pipe.
Can't i just put a reducer right into the drain so it's 1 and 1/2 the whole
way?
I watched video of a tile installer doing just that.

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Unread 01-04-2020, 09:40 AM   #6
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I prefer the Durock Shower System membrane to the orange membrane, George, and you can get everything you need from Amazon. Depending upon the size of your shower you should be able to get all you need, which is a drain, drain grate, and sufficient membrane, for under 200 dollars.

You'll want to talk with your local code compliance official before you commit to this project, but the only place it will be code compliant for you to reduce that drain size is directly at the drain, which will be sized for a 2" pipe. The best fix is to increase the size of the existing drain line to 2 inches, but that's not legally necessary unless you plan more than a single shower head in the shower.

My opinion; worth price charged.
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Unread 01-04-2020, 10:30 AM   #7
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Thank you,

So, i can keep the inch and a half drain line and put a reducer on directly at the drain?

Do i need to know what drain type i am using before i fill in the trench?
I have familiarized myself via youtube to the locking flange type that the
liner goes in and i can get a drain at the borg today and feel like i am moving.
I tore out the tub yesterday and need to keep this moving as it is the only
bathroom in the house.
It would be great if i could fill the trench today but still keep options on the drain/pan system.


Cheers
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Unread 01-04-2020, 10:49 AM   #8
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1.
Quote:
Originally Posted by George
So, i can keep the inch and a half drain line and put a reducer on directly at the drain?
Quote:
Originally Posted by CX, Post #6
You'll want to talk with your local code compliance official before you commit to this project
2. I would.

You need to decide what waterproofing system you intend to use before you start installing drains, George. No matter how urgent the project seems. The hurrier you go, the behinder you're likely to get.
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Unread 01-04-2020, 11:44 AM   #9
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Great!

I was worried i might have to break up the floor in another room to find where
the tub connects with the main drain pipe.

I will definitely look into the durock system when i get home tonight.
I did watch a video by the popular Youtbe tile setter whopahks his cah in the Hahvahd yahd doing the Kerdi system.

The thing i didn;t like was it seemed thinset was the ultimate barrier to water.
He covered his walls and floor with flat pieces and then thinsetted corners all
around the bottom of the pan.
I thought cementious materials wicked water?

I will broach the idea to the customer/relative though.


The Durorock membrane looks more non-cost-prohibitive.

3/4 inch bed plus slope as opposed to 2 1/4 inch bed plus slope seems worth
the money for the increased safety and accessibility.

I wish i had time to study it to better sell it to her.

Thanks man, i could never do this alone and this forum lowers the stress somewhat.
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Unread 01-04-2020, 12:31 PM   #10
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A link to the youtube video you saw would help us evaluate what you saw. While there are good videos out there for the use of ceramic tile installation products, there are far more we'd rather you not follow.
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Unread 01-04-2020, 02:15 PM   #11
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Can't find the particular video.
It's Sal from Bahstin, his videos always come up in the recommendations when
watching tiling videos.
He thinsetted a sheet of that membrane to the floor and then used narrower
pieces like drywall tape around the edges.
Thinset behind and on top, iirc.

I guess i'll trust it works and push it for the 1 and 1/2 lower entrance.
Right now it is hardly lower than the old fiberglass tub.
She had someone cut it and add this pre-made step in the notch.

I don't like having order though, it's more comforting knowing everything
is gettable whilst working.

Can you use a Kerdi drain with teh Durarock membrane?
I don't think she will like that grate on the Durock.

And is the Kerdi and Durock systems installed similarly? I am not finding
any Durock videos.
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Unread 01-04-2020, 03:33 PM   #12
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Sal DiBlasi's videos are usually correct.

The Kerdi drains also have a square grate.

The installation process is similar with both those membranes.



My opinion; worth price charged.
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Unread 01-05-2020, 07:40 AM   #13
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Thank you,


She is pondering using the Durock membrane.
One fifty foot roll should do it and the price is comparable to a
pvc liner and Redgard walls.

So what besides the membrane and drain do i need to order?

And for the entrance; by my calculations the 3/4 inch bed plus slope (30 inches to either side of drain) would
be about 1 and 3/8 above the floor in the greater bathroom.

I would like to go curbless though there would be that 1 3/8 raise coming in.
Do i still put in a curb like normal only the top is level with he shower floor?

Is there like a rubbber sweeper that goes on the bottom of the door for
curbless entrances?



What is the reason the deck mud can be so much thinner when using a membrane?


When you do rebar doweling do you oversize the holes and fill them with
something?
I will have some anchoring epoxy for the knee wall i could put in with the rebar as well.


Thanks again
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Unread 01-11-2020, 09:42 PM   #14
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Okay, we are doing the Durock sheet membrane.
I am going to do the deck mud shower pan tomorrow.
I have bought an un-modified thinset called Uncoupling Thinset from Mapei.~
https://www.lowes.com/pd/MAPEI-Uncou...ortar/50157886

Can i use this as the slurry between the concrete and deck mud or do i need
modified for this part of the job?

How loose should this thinset slurry be?


I was planning on using Mapei deck mud as well as Lowes is real close to the
house.
It is stated to be 4 sand to 1 cement.
Do i need to add sand to this?
Does the type of sand matter? I have some fine silica on hand.

Thanks
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Unread 01-11-2020, 11:08 PM   #15
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Quote:
Originally Posted by George
What is the reason the deck mud can be so much thinner when using a membrane?
The deck mud can't actually be thinner, but there is only one layer.

Quote:
Originally Posted by George
When you do rebar doweling do you oversize the holes and fill them with something?
I will have some anchoring epoxy for the knee wall i could put in with the rebar as well.
I generally drill them the nominal size of the rebar dowels and drive them in. Drilling at an angle and bending them to their final orientation generally gives a good mechanical bond.

You can drill larger and use epoxy if you like.

You can use that thinset mortar for your bonding slurry. I like thick tomato soup as my slurry consistency.

If you use a proprietary deck mud you use it as the manufacturer instructs.

My opinion; worth price charged.
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