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-   -   How to slope for an offset linear drain? (https://www.johnbridge.com/vbulletin/showthread.php?t=119907)

CaliGrown 05-17-2016 11:21 PM

How to slope for an offset linear drain?
1 Attachment(s)
Hi I am new here, and hope this post isn't too far off from the thread guidelines.

I am currently in the process of doing a shower pan replacement and have some questions about sloping the deck mud. The homeowner has moved the abs drain pipe over right next to the side wall toward the end of the shower with the valve and shower heads. Since there was a joist and part of the foundation blocking the path to set the drain pipe toward the most preferable location, directly against the back wall with the shower valve and heads, he decided to place it on the side wall. Given this drain location, I plan to slope the deck mud in four regions all toward the linear drain, please input any thoughts to best accommodate the sloping.

Conditions of the job:
Using a Cohen 24" Signiature Hardware Linear Drain, it's installed according to installation instructions in the 3 part drain assembly flange and has a height of above 1.5" from the base of the liner.

Using pebbles for the shower pan, they range from about 3/16" to 5/8" in thickness, game plan is to remove all of the rocks from the mesh and installing them individually to improve the tightness of the joints and improve the size and color disbursement of the pebbles.

Wall tile is a 12" by 24" porcelain laid in a staggered running bond pattern.

Current state of the jobsite; the pre slope is completed at 1/4" per foot toward the drain flange, 40 mil Oatley liner installed, I took it 8" up on all of the walls and wrapped around the curb, installed corner patches on the corners wrapping the curb, galvanized nails were used to fasten the liner on the outside face of the curb. For the walls, the previous "installer", had installed .42" hardibacker over 1/2" drywall with thin set, which didn't bond to the hardi board (trowel ridges weren't even compressed down) and only a handful of fasteners were found. I would prefer a complete replacement, but since the homeowner only wanted the pan replaced, we decided to take off the first two corses of tile and replaced the drywall and hardi board, with cement board and hardibacker to maintain the wall thickness. I left about a 1/8" space between the separate planes of the walls, and filled it with 100% silicone to act as a cold/expansion joint, next I applied three coats of red guard over the hardi board to waterproof the hardibacker. It is ready for the top deck mud, which I need help sloping...

Since using pebbles in the pan, is 1/4" per foot adequate or should I do closer to 3/8" per foot?

I plan to have the drain set 1/16" to 1/8" below the finished height of the pebbles.

Attached is a picture of the layout. What would be the best way to slope the mud? I am thinking the large middle section to slope as a trapezoid, and the two sides to slope as angled triangles and the mud behind the drain to slope as a tilted rectangle. Please leave suggestions, if any other info is needed, let me know.
Attachment 186289


Tiger Mountain Tile Inc 05-18-2016 08:43 PM

Hi Chris and welcome to the forum! :yo:

With that sort of a set up I think you have to slope all walls into the drain. Really it isn't much different than a normal round drain as far as building the shower goes.

With pebbles I would encourage 3/8" per foot. They just don't drain as well as flatter tile.

CaliGrown 05-18-2016 10:17 PM

Thanks for the reply Jim,

Thats what I planned on doing with the slope. When sloping all the walls toward the drain; since the distance from the drain varies from wall to wall, the mud would have directional slope toward the drain at each point away from the drain. Wouldn't this make it so that the mud would not have a horizontally level perimeter along each of the walls, aside from the 2.5" section of mud directly next to the linear drain?

Thanks for confirming a 3/8" slope for the pebble tile. Normally I install the wall tile after the shower pan tile, but after seeing pictures of pebble installs, it looks like the pebbles are installed after the wall tile, is that right? Would assume to caulk the joint between wall and pebbles after grouting the walls and pebble floor.

Thanks again,

jadnashua 05-19-2016 04:30 PM

Does that linear drain have weepholes? If not, how is the water beneath the top supposed to drain out?

Industry standards call for caulk at all changes of plane, which would include wall/floor and wall/wall.

With REdgard on the walls and them sitting in the pan (you do know that Hardie does not allow HardieBacker to be installed IN the pan - it must end above it), any moisture that got into the pan can weep up behind the waterproofing layer and make a mess of things. Hardie is in the class called fiber-cement boards, and those cannot be inside of the pan, only to be used when terminated above the pan.

CaliGrown 05-19-2016 04:57 PM

Yes there are weep holes. It's a standard three part drain assembly.

Alright, I have the matching caulk.

After installing the liner, I cut the cement board longer than the hardibacker, so that the it would extend past the hardibacker when it was installed on the walls. I have the hardibacker cut so that it will finish about 3/8" above the finished height of the pan.

I have some Kerdiband leftover. As an extra precaution for waterproofing. Would it be a good idea to do the seam between the pan and the walls, or is that overkill?

Thanks again

rjwz2 05-19-2016 05:20 PM

Sorry to highjack your posts but Jim made a comment about Hardiebacker in the pan that confused me.

Jim, I am building my shower right now and you state that Hardiebacker cannot go into the pan? Please explain what you mean. I am doing my shower also with pebbles for the floor on a mud pan that I just finished. I was going to mount 1/2" Hardiebacker on the studs with Redgard on it and bring the whole wall down to I/4" above the mud pan floor and silicone that space. The membrane goes up the studs around 8" I thought I've seen this done many times and it seems like you say that not to do this. I am confused. Am I missing something? Could you please elaborate?


jadnashua 05-19-2016 05:21 PM

Kerdi seams work by the close proximity of the two layers in an overlap of the fleece fibers. I don't know how well it would waterproof things if one side was REdgard, unless you applied redgard over the top of the edge of the Kerdiband.

You can get unpredictable results when you mix products.

Generally, not a great idea to waterproof the walls with a surface applied material and combining it with a conventional liner...the lower edge of the wallboard will still be exposed to the mudbed, and now, you've trapped that moisture behind a waterproofing layer.

CaliGrown 05-19-2016 05:42 PM

You raised a great point about the moisture being trapped behind waterproofing layers. I'm thinking the best option for me then would be to waterproof the cut edge of the hardibacker then install the pan without putting a band of redguard or kerdiband along the seam. The liner would then be free to move absorbed water along to the weep holes, without there being compromising moisture in the trapped in the hardibacker behind the redgard.


CaliGrown 05-19-2016 05:49 PM

What Jim is referring to is to install the hardibacker above the mud pan, so that the boards aren't sitting in the mud, and can't absorb moisture in from the pan. As a extra precaution, applying redgard on the cut edge of the hardibacker wouldn't hurt to eliminate entry points for moisture, should water ever get between then silicone bead between the pan and hardibacker.

rjwz2 05-19-2016 11:46 PM

Ok, got it Chris. Sorry to high jack your thread.

Thanks, Rob.

CaliGrown 05-20-2016 12:51 AM


You didn't high jack it, we both got questions answered.

Best of luck with your shower

CaliGrown 06-04-2016 03:27 AM

Pictures of the completed repair
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Changed out first two courses of wall tile, replaced tile and stone on the curb. Installed pebble tile, wound up having two different types of rock so we blended them together, since they didn't want to send it back to get the other rocks. Too much of a wait... But it will do.l. Happy it's over with, onto the next

CaliGrown 06-22-2016 09:37 PM

Too late to add?
1 Attachment(s)
Finished the shower today and now the homeowner wants to add a shelf in the niche. What is the best approach to adding the shelf, if that's an option? Shower is grouted, I figure cutting a slot in the back of the niche along the mosaic and using epoxy to set the shelf. For the shelf I am using a piece of marble that I polished the bottom of and face of. Any thoughts are well aprreciated. Thanks in advance. Also, the Homeowner does not want the bullnose pieces of the niche to be slotted for the shelf if possible.

jadnashua 06-22-2016 10:35 PM

KerdiFix, once cured, has over 1200psi bond strength. If you support things well while it cures, I'd feel better about it than epoxy...the slight flexibility may be an advantage over epoxy's stiffness. Comes in white and grey.

Steve in Denver 06-22-2016 11:39 PM

My shower glass is held in place significantly by the silicone running along the curb and up the wall. If you have some silicone that is color matched to the grout, I'd think that would be an option to consider. Not a whole lot of weight that shelf has to hold.

I like the look of that mosaic in the niche, BTW.

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