Is installing a shower base with a mm or under tolerance for vertical movement (bend) at the center

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Mini Me

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I wasted almost half of a bag o fast setting concrete trying to do what the manufacturer is asking

6NFY4UPl.png



and it is not working. The shower base sits on a perfect flat surface because I poured self leveling concrete. If I measure the levelness corner to corner it is almost perfect, it makes no sense to fight to improve it

The shower base will have two glass panels (it is a corner setup) and as of know it is by itself very heavy, you can't push it around when you sit on.

You can hardly push a scrapper under it in at the median point of the long edge of the shower base
I have looked at it and when you press on it on the center point of the shower base the corner points to not move at all and the short edges stay on the floor perfectly flat and level.

The drain does not move when you step on the shower base, it is just this very small space at the median point of the long edge that closes and then it is perfectly flat there as well. I suspect that gap will close completely when the glass panels will sit on it

As far as I can see I won't be able to fine tune the concrete mounds or the way the shower base sits on this concrete in order to offer support AND to make those shower edges sit perfectly flat on the floor.

How much can I improve this situation ? What else can I do? ? One thing that I am considering is to pour again self leveling cement that is pretty liquid and it it will go under that base and support it . In order to do that I will have to lay down plastic sheet on the exterior perimeter of the shower base and then fence the same perimeter like 1 in away from it and pour the self leveling concrete there. The plastic or maybe tape will make sure I can remove the self leveling concrete after it is cured and the hope is that it will leak under the shower base and support it from below

The other option is to trust the level that the floor is flat and to assume that the base is bent a little and it will flex and follow the floor once it is loaded with the glass panels. If there is any jiggle room left when loaded with the glass panels it will be in the center. I am assuming that the edges adjacent to the wall will get some load as well from the cement boards on that wall, although it might not happen as the cement board might be above the flange but not sitting on it
 

Jeff H Young

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A book kind of looses me? what is the problem ? the floor is flat I get it, is the shower pan flat? you put mud down ok , if the mud is flat and dry why not put liquid nails or adhesive.
 

Mini Me

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A book kind of looses me? what is the problem ? the floor is flat I get it, is the shower pan flat? you put mud down ok , if the mud is flat and dry why not put liquid nails or adhesive.
I have the impression that the shower base is not 100% flat
 

wwhitney

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What does the underside of the receptor look like? It sounds like it just has 6 feet that are to make contact with the subfloor, which is why they direct you to use 6 mounds. Are those 6 feet coplanar?

If there are just 6 feet, I'd suggest a test fit with a way to tell if the six feet are making contact. Maybe perfectly identical thickness shims at the foot locations, so you can peer under the base to see all the feet are contacting the shims. Maybe a transfer medium put on the feet, that you check is transferring to the floor at all the foot locations.

I think you mentioned a gap along one long edge between the pan and the floor. If everything else is in good contact, just set the pan and then fill the gap afterwards with a suitable material, before the weight of the glass is on it. The glass may deform the edge to make contact, but I don't see any upside to stressing the pan.

Cheers, Wayne
 

Mini Me

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Below are 'schematics' from their manual
Mine is the left side drain
UI could fill that gap with spray foam or self leveling cement so that in the case of any uneven contact it will sneak in and under the shower bed and support it from there
I also considered shims but it is very difficult to control their thickness and position to get it right.
I tried 1/16" shims that I cut with my table saw a while ago


kIwJA.png
 

Terry

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If it's that level with no gap to speak of, then I also go with the construction glue.

Mortar is nice with out of level flooring, and pans with large gaps.
 

jadnashua

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The undersides of most pans are not flat, and unless made out of cast iron, tend to flex when standing in it, so the mortar underneath provides two functions, and you may not need the second...it provides support so the pan is less likely to flex, and, where necessary (and it is most of the time!) it allows you to level the pan.
 

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This one is enameled metal and the bottom side is made of some solid yet a little bit flexible plastic that follows the contour of the same metal
The back side is not flat it has a pattern of gaps where the cement mound is supposed to get in if used. Imagine a honeycomb structure with walls of like 1" thick between the hexagonal cells (they are not hexagons in my case but that does not matter)

Using adhesive/glue might present a problem later if I need to open it up and intervene to change something there

The self leveling concrete has the ability to try to get into the spaces where it can and that is all I need, to pour a thick layer patch in the middle where the base needs support and then wait for it to self level and enter the adjacent cells of the honeycomb if there is room between the bottom of the shower base and the floor. Obviously that will be where support is needed and hopefully the concrete won't move from there
It could also happen that the concrete will self level to the point that it will be too thin and it will offer partial support.
 
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Mini Me

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What could be alternative to construction glue that would remain in position but without permanently gluing the thing to the floor ?

I need something that would create a sort of mold for the base in the median part of it and won't move around
I expect the shower base to create the mold by its own weight. the this should be liquid enough to create the mold but then strong enough when it cures to create the mold and stay like that
 

jadnashua

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Self-leveling cement is a misnomer...it does not totally self-level without help (think pancake batter), and is too runny to try to contain underneath the new pan.

By putting the piles of cement in the appropriate places underneath the pan, you'll support it from flexing, which, over time could cause spider cracks and eventual rusting and failure. The whole thing will feel much more robust when supported as specified. Leveling is a bonus, if necessary. Enameled steel would not be my first choice of material...it's fairly easy to chip the finish if you drop something hard on it, and then it rusts. The finish may be harder than an acrylic pan, but as a result, it's brittle and the steel isn't all that thick, so can dent or flex.
 

Mini Me

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Hmm I realized that one way to deal with this is to use very thin tin foil like the one used for flashing
I tested this with one layer in the median section -it was moving free under the base in all directions excepting the corners and the end edges
So I put two layers one on top of the other and the situation improved radically, the shower base was not moving almost at all
I guess putting three or four transversal sandwiches like above describe will totally stabilize the base

Here is a visual
z6KuuXUl.png
 

Mini Me

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Self-leveling cement is a misnomer...it does not totally self-level without help (think pancake batter), and is too runny to try to contain underneath the new pan.

By putting the piles of cement in the appropriate places underneath the pan, you'll support it from flexing, which, over time could cause spider cracks and eventual rusting and failure. The whole thing will feel much more robust when supported as specified. Leveling is a bonus, if necessary. Enameled steel would not be my first choice of material...it's fairly easy to chip the finish if you drop something hard on it, and then it rusts. The finish may be harder than an acrylic pan, but as a result, it's brittle and the steel isn't all that thick, so can dent or flex.
I think I got the material wrong here is the link
https://www.kohler.ca/ca/ballast-60...d-drain/productDetail/shower-bases/429197.htm

and here is what they say

  • Low-threshold design for easy entry and exit.
  • Single threshold for alcove installation with integral tile-in flange.
  • Durable acrylic with resin concrete core construction.
  • Allows for quick and easy mortar-less installation.

While working of the framing and trying to make it straight and to allow the shower base to get closer to the wall I plugged in the power outlet a Dremel 4000 that was left on with a circular blade for wood on it and it started spinning and it made a scratch on the surface. It is small and I thinkI can polish it to disappear so it is not enameled but it looks like it

Oner thing is for sure it is heavy and it does not look and feel cheap like the plastic ones ..it did not come cheap either I think I got it before Covid for 600-800 CAD. It is like 1100 CAD now
 

Mini Me

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What I am not sure is if the aluminum tin used for flashing will react in any way with the cured concrete (self leveling concrete was poured months ago on that floor)
 

John Gayewski

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Use a notched trowel and mortar. The spaces between the rows of mortar will allow you to set the base like a giant tile. You can tap and adjust the pan to level as it sets into the mortar. This is how I like to set shower pans that apply to this method. You could also just set a bed of mortar and use your finger or a tool to make raised rows.
 

Jeff H Young

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Mini me , you got this ? you could lay a sheet of plastic over glue or morter, if you are concerned about it sticking . which I have no idea why its an issue , I mean its not a temporary job .
 

Mini Me

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Mini me , you got this ? you could lay a sheet of plastic over glue or morter, if you are concerned about it sticking . which I have no idea why its an issue , I mean its not a temporary job .
No but I am DIYer and who knows what and if I got anything wrong under the shower base (there is plumbing there ABS drain p trap, a segment a wet vent, you alredy know about these since we discussed what I did there a while ago
 

Mini Me

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Use a notched trowel and mortar. The spaces between the rows of mortar will allow you to set the base like a giant tile. You can tap and adjust the pan to level as it sets into the mortar. This is how I like to set shower pans that apply to this method. You could also just set a bed of mortar and use your finger or a tool to make raised rows.
The adjustments I need to make arw under 1/16"...just think about it I can slide under this base flushing tin, one layer, it is moving kind of free under the base. If I put two layers they get stuck and it seems it stabilizes the base, no more bending. It will get two shower glass pannels on top so there is no chance this will move and it will stay 1/32" compressed downward at most..
I wont be able to get the precision I get with the aluminium foil by using mortar.
I cant go upward (float the base) too much becauee then that defeats the purpose of having a lower threshold base. You can ask me to raise the floor level to follow the base lifted by too much cement put there but that will force me to deal with the issue of having the bathroom floor to high compared with the hallway floor level and this way I will extend the problem to the entire basement floor
 

wwhitney

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Against concrete galvanized is better than aluminum, but if the aluminum is painted that would provide some barrier to corrosion.

I like the notched mortar idea, like you were setting tile. A plastic sheet above or below the mortar would be a bond break.

Cheers, Wayne
 

Mini Me

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I could use the plastic idea with aluminium as well Yes the flashing tin sold in coils at HD is painted
 
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