Ceramic Tile Advice Forums - John Bridge Ceramic Tile

Welcome to John Bridge / Tile Your World, the friendliest DIY Forum on the Internet


Advertiser Directory
JohnBridge.com Home
Buy John Bridge's Books

Go Back   Ceramic Tile Advice Forums - John Bridge Ceramic Tile > Tile & Stone Forums > Tile Forum/Advice Board

Sponsors


Reply
Thread Tools Search this Thread
Unread 08-11-2022, 12:11 PM   #1
mjl975
Registered User
 
Join Date: Aug 2022
Posts: 10
Mortar shower pan deflection

Hi everyone, I've been working on a dry pack shower pan, built up from a pre-slope, liner, and about a week ago placed the final mortar bed. Today with everything set up I notice that there is a very slight deflection in the bed at a few points around the edge and in the corners. I can only imagine that this is due to the pan liner not completely seating at these areas, forming an air pocket underneath. I did have a slight crease in the center that wouldn't work out, and of course with the folded corners it's impossible to get it to conform perfectly to the pre-slope. So...naturally I'm wondering if this is common and acceptable. The subfloor is 2x6 T&G on 16" joists, so I'm positive the floor is absolutely solid. The deflection in the mortar isn't enough to crack it, but it's obviously there, as the loose flap of pan liner running up the wall flexes a little when I step down. The bed is about 1.25" thick, and the pre-slope is about 1.5" thick around the edges. Leave it? Tear it out and re-do it? If re-doing it, how to avoid this on the next try? Thanks for any advice!
Attached Images
  
__________________
Marc

Last edited by mjl975; 08-11-2022 at 01:20 PM.
mjl975 is offline   Reply With Quote
Sponsored Links
Unread 08-11-2022, 04:01 PM   #2
Davy
Moderator -- Mud Man
 
Davy's Avatar
 
Join Date: Jan 2003
Location: Princeton,Tx.- Dallas area
Posts: 34,088
It really depends on how much "slight deflection" is. Did you staple tar paper (or poly) and lath to the plywood before placing the preslope? Not sure if that is part of the problem or not. Lots of plumbers never staple lath down but most tile installers do.
__________________
Davy

www.davystephenstile.com
Davy is offline   Reply With Quote
Unread 08-11-2022, 04:19 PM   #3
Lazarus
Texas Tile Contractor
 
Lazarus's Avatar
 
Join Date: Oct 2006
Location: Beaumont, Texas
Posts: 8,726
When you say "deflection," is it just a matter of the liner being a tad loose? When you push on it, does it just lay flat or does the floor actually move down a bit when you step on it? If the liner is all that moves, when you set the final mud bed...that should draw it down. If that's the case, you're good to go.
__________________
You can have peace. Or you can have freedom. Don't ever count on having both at once.”
Lazarus is offline   Reply With Quote
Unread 08-11-2022, 07:28 PM   #4
mjl975
Registered User
 
Join Date: Aug 2022
Posts: 10
I put 6mil poly in place before the pre-slope, but no lath.

The floor actually moves down a tiny bit when I step on it. It's really not enough to see, but the loose edge of the liner moves so I know it's happening. And this is with the final mud bed. Next step would be tile. That's why it worries me a little.
__________________
Marc
mjl975 is offline   Reply With Quote
Unread 08-11-2022, 08:10 PM   #5
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 95,748
Welcome, Marc.

We've known folks to place a pre-slope without the requisite metal lath and have the shower survive. Not the best idea, though.

I'm curious why you've placed your final mortar bed before installing your wallboard. You don't plan to use a type that can be bedded into the final mortar to support the bottom edge?

The minimum thickness for the top mortar bed is 1 1/2 inches. That's not likely to help at all with your movement problem, though. And any perceptible movement is not acceptable for your ceramic tile installation. Definitely need to get that sorted out before you go any further.

I'd also like to know if you've notched out the bottom of the studs to accommodate the waterproof liner, 'specially there in the corners where you've got folds.

A larger concern I note is the treatment of the liner at the ends of the curb. Doesn't appear that it's been cut and folded there in such a manner as to allow you to install some dam corners to complete your waterproofing.

And please tell us your plan for waterproofing your shower walls.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is online now   Reply With Quote
Unread 08-11-2022, 10:10 PM   #6
mjl975
Registered User
 
Join Date: Aug 2022
Posts: 10
Thanks for the feedback.

I didn't plan to embed the cement board in the mortar. Wonderboard (which is what I'm using) doesn't specifically say not to, but some others (Hardibacker, for example) and many tutorials do specify a minimum 1/4" gap between mortar and the board's edge. So I figured, why not? Hardi even says specifically not to embed their board in the mortar bed (and this is for their "waterproof" Hydrodefense stuff). Most also spec that a silicone sealant fills the gap before tiling.

I have notched out the studs 1/8" for the liner, but probably should have done a little more in the corners at the folds. I can still do that in any case.

I've been able to install the dam corners at the curb. The photos don't show it because they were taken beforehand.

The plan is to use a couple coats of Redguard for waterproofing the walls before tiling.

If I could post videos here I could show the amount of "flex" in the pan. It seems to me that it's enough to cause problems with the tile, but I guess I'm hoping to hear, nah, don't worry about it. Hah! I'm OK with re-doing it, but don't want to get the same results again. Maybe my mortar was too dry and the final product isn't totally cohesive, allowing for the flex. So a little more water? Also possible a more consistent adhesive for the liner, especially at edges and corners, although I don't see anyone else going to this extent.
__________________
Marc
mjl975 is offline   Reply With Quote
Unread 08-11-2022, 10:36 PM   #7
mjl975
Registered User
 
Join Date: Aug 2022
Posts: 10
Oops, forgot about the lath. My concern with putting lath in the pre-slope was that the slope tapers to about 1/8" at the drain flange, and no way could I get lath in there at that thickness. Possibly end it before the taper gets too thin to conceal it? What is the standard practice with this?
__________________
Marc
mjl975 is offline   Reply With Quote
Unread 08-12-2022, 06:31 AM   #8
Just In Tile LLC
Registered User
 
Just In Tile LLC's Avatar
 
Join Date: Sep 2015
Location: Palestine, Texas
Posts: 1,671
Marc, it sounds like the info you've given only digs the issues deeper . When we set the drain we make sure to set it high enough to allow for the lath AND preslope minimum required thickness with lath which is 3/4".

I believe CX was referring to your lack of liner at the top of the curb to bond your corners too. What we see is just wood which means you have stapled the corners there and glued them (I guess) to the part of liner left on the top and inside of the dam. We see alot of water damage in that spot upon tearout of old showers so it's good to have more liner there. When you cut it proper theres liner all the way to the outside of the dam.

Most on the forum err on the side of caution (for good reason) so I think with what you've said a thumbs up won't happen. In our minds it's so easy and cheap to fix now before the high dollar materials start happening.
__________________
Justin
"Being world class means knowing you're good, but never satisfied you're good enough"
Just In Tile LLC is offline   Reply With Quote
Unread 08-12-2022, 09:11 AM   #9
mjl975
Registered User
 
Join Date: Aug 2022
Posts: 10
Hi Justin, thanks for the reply. How do you set the flange higher? As it comes, it appears that it screws directly to the subfloor, and there's not a lot of height there when that happens. The screw-in drain grate can be adjusted a lot higher, of course, but that sits at the final grade, not at the pre-slope.

The curb is completely covered in liner. The corners are bonded to that surface and to the liner in the corner behind the fold. I'll try to get some better pictures. It appears to me to be waterproof, but I could certainly be wrong.

I think I will tear out the final mortar bed at the very least and inspect things from there before deciding what to do next. I'd rather not tear out the pre-slope and liner, but will do so if necessary.
__________________
Marc
mjl975 is offline   Reply With Quote
Unread 08-12-2022, 09:20 AM   #10
mjl975
Registered User
 
Join Date: Aug 2022
Posts: 10
This is a stock photo, but it's basically what I'm working with. Once screwed to the floor, it's almost flush.
Attached Images
 
__________________
Marc
mjl975 is offline   Reply With Quote
Unread 08-12-2022, 12:30 PM   #11
mjl975
Registered User
 
Join Date: Aug 2022
Posts: 10
OK, I tore the top mortar bed out. Not surprisingly, it mostly just crumbled. Definitely looks like not enough water. I was afraid I had damaged the pre-slope by breaking up the top bed with a hammer, so I removed the liner. To my surprise, the pre-slope looks fine. No cracks, and a definitely less-porous appearance. Probably got the mix right on that one. Stepping on the pre-slope at the edges and corners doesn't appear to cause any deflection, so I think the problem was in the top bed, with its crumbly, porous consistency.

So...I've attached some pictures here. One that shows the consistency of the broken up mortar. One of the corner dams before I tore the liner out (I did a messy job on these, will do better on the re-do). One of the drain flange and the pre-slope's taper to it (still need to scrape off the old silicone). One of the pre-slope after the liner was removed. Any comments or suggestions would be appreciated, if I need to do something differently when I put the liner back in. Since the pre-slope looks intact, I'd rather not tear it out, however.
Attached Images
    
__________________
Marc
mjl975 is offline   Reply With Quote
Unread 08-12-2022, 02:59 PM   #12
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 95,748
Quote:
Originally Posted by Marc
I tore the top mortar bed out. Not surprisingly, it mostly just crumbled. Definitely looks like not enough water.
Only thing that looks wrong to my eye is the thickness, Marc. Unlike the pre-slope, the top mortar bed is designed to be porous. Traditional shower receptors are a water-in, water-out design and the mortar bed needs to allow water to pass easily through it.

The required thickness of the top mortar bed, according to tile industry standards, is a minimum of 1 1/2 inches and is to be of consistent thickness to follow the slope of the waterproof liner.

Your liner installation, aside from at the curb ends, looks OK from here, but I can't tell if it might be hanging from the fasteners in the corners where you detected movement. You want to be sure that's not the case.

And at the curb ends, you really want it to cover both the horizontal and vertical surfaces such that your dam corners are serving only to seal the horizontal cut across the curb. There should be no vertical cuts in that area.

And, again, it appears that you have no room cut into the bottom of your framing to accommodate the liner material and keep it from making your wallboard bow out at the bottom. Easy to do in your current situation.

As for the bottom of the wallboard, you cannot use mechanical fasteners anywhere below a level line two inches above the top of your curb. If you're using Durock you can certainly bury the bottom edge in your top mortar bed for support. That is not true for the Fiber/Cement boards (Hardiebacker, etc, ASTM C1288), but the true cement boards (ASTM C1325) can be done that way with good result.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is online now   Reply With Quote
Unread 08-12-2022, 04:27 PM   #13
Just In Tile LLC
Registered User
 
Just In Tile LLC's Avatar
 
Join Date: Sep 2015
Location: Palestine, Texas
Posts: 1,671
The drains I use Marc have a cavity the bolts screw into which when I cut the hole for the drain I don't cut out for those cavities which stick down about 3/4" from the flange so the drain actually sits on the screw cavities. The screws end up being exposed partly before they screw into the wood. This allows me to stuff all my mud under the drain flange and meet (or closely meet) that 3/4" minimum. I'll see if I can find pictures.

Personally I would feel confident in laying the liner with the preslope you have there but it's technically not minimum standards. I mean where's it gonna go?

I've looked up approved adhesives for the liner and remember liquid nails being one of them, I end up adhering my liner to my dam with whatever silicone I'm using to lay the liner in at the drain manifold. The liner is super tight to my curb so I can mud it thinner plus the wire sits nicely on it.
__________________
Justin
"Being world class means knowing you're good, but never satisfied you're good enough"
Just In Tile LLC is offline   Reply With Quote
Unread 08-12-2022, 05:02 PM   #14
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 95,748
Quote:
Originally Posted by Justin
I've looked up approved adhesives for the liner and remember liquid nails being one of them...
Who approves that, Justin?

Only adhesive I know of for PVC liners is Oatey's X15. I'm sure there are other brands, but I'm not familiar with any.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is online now   Reply With Quote
Unread 08-12-2022, 07:25 PM   #15
Davy
Moderator -- Mud Man
 
Davy's Avatar
 
Join Date: Jan 2003
Location: Princeton,Tx.- Dallas area
Posts: 34,088
This is what Justin is talking about.
Attached Images
 
__________________
Davy

www.davystephenstile.com
Davy is offline   Reply With Quote
Reply

Stonetooling.com   Tile-Assn.com   National Gypsum Permabase


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Masonry mortar use as cement mortar for shower tile eyeglass Tile Forum/Advice Board 46 10-31-2010 10:32 AM
Yep, another Shower build-deflection help DoofusOfTheDay Tile Forum/Advice Board 36 07-30-2006 02:31 PM
Deflection for mortar bed, slate floor Mitch_Skool Tile Forum/Advice Board 2 01-06-2006 10:24 AM
mortar bed shower floor - what mortar? Brett J Tile Forum/Advice Board 6 10-02-2005 07:40 PM
Steam Shower - Drywall deflection cliffbrown Tile Forum/Advice Board 5 03-24-2005 11:55 PM


All times are GMT -6. The time now is 09:23 AM.


Sponsors

Powered by vBulletin® Version 3.7.4
Copyright ©2000 - 2022, Jelsoft Enterprises Ltd.
Copyright 2018 John Bridge & Associates, LLC