Shower Pan Mud Bed Problems


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Old 01-23-23, 01:04 PM
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Cool Shower Pan Mud Bed Problems

Hello all, New to this forum. I am having serious reservations about the outcome of my bathroom shower remodel project. It is actually a new shower in a different part of the old bathroom. I have reviewed many online videos of how to do the whole thing.
So i built the enclosure and curb etc to specs and did the preslope using that green bag of mortar mix that was highly recommended on the videos i watched. I did notice that the preslope mud bed seemed to be kind of weak and the top just peeled away like brushing sand off a board. However, i just figured that was ok cause no video seemed to make an issue of it.
Then i installed the 40 mil plastic pan liner as seen on these videos. Next, i used that same green bag of mortar mix to make the shower pan just like in the videos. I let it dry about 12 to 14 hours and proceeded to lay the floor tile, a hexagonal pattern mosaic tile. First thing i noticed was how crumble the mud bed was. I tried brushing the loose sand off the bed and it just kept coming off the bed. So i left it alone and started trying to lay down the thinset and it just rolled up in the sand off the top of the bed!
So, my question is, what went wrong? if anything. I did everything just as the videos said to do. Surely i am not the only one who has had this problem?
 
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Old 01-24-23, 07:50 AM
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The preferred mix is something similar to Quikrete Sand/topping mix. Don't know the color of the bag, I'm color blind. And you most certainly do mix it dry enough to form into a ball just as you said, it should be damp, not wet. My only guess would be you didn't wait long enough. Some sand will still come off after 12 hours, you can correct any imperfections by block sanding at this time. 24 hrs is better before you start tiling. But depends on drying conditions and how wet it is.

Also no idea what your video said, how good the advice was or how well it was followed... but if you haven't read it yet, the floor elf site is the best one out there for instructions on making a mud bed. (He has a section on deck mud) It also mentions how you will experience some sandy texture in the surface, but imo what you are experiencing is from working on it way too soon.

If you did it correctly, it's probably good to work on by this time now.
 
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Old 01-25-23, 08:09 AM
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Unless you have a family size 12" thick pan your probably good.

Think how heavy a whirlpool tub is sitting in a bathroom and not many homes collapse from that!

YouTube video's should be viewed with a grain of salt, if that.

 
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Old 01-25-23, 09:33 AM
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I'm surprised that people are still using old school mud beds for showers when there are so many easier and quicker options available. Products like Kerdi and Tile Redi are just about fool proof.
 
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Old 01-23-23, 01:19 PM
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Not an answer to the specific question but mud beds are difficult at best.

The pre shaped Styrofoam inserts are a snap to work with!
 
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Old 01-23-23, 03:15 PM
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"...what went wrong?"
The only information you provided about the construction is "... on the videos" and "green bag". Not much to go by. I suspect you did something incorrect with the green bag. Maybe used too much or too little water. It can also happen if you continue to mix/work material that is hardening.
 
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Old 01-23-23, 04:03 PM
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The green bag is a premixed mortar mix (in a green stripe bag by Quikrete) from HD and is recommended by many sources on the internet as sufficient to construct both a preslope and the dry pack shower pan. They also make a stronger mortar mix in a bag with a RED stripe, but NO ONE recommends it for shower pans, not sure why. As to mixing, the instructions are (again on many videos on youtube, just type in "How to make a mortar bed shower pan), to mix with enough water to form a ball in your hand that won't come apart when you toss it in the air. Not much can go wrong with that.
The problem seems to be that the mortar never hardens and i am just asking if this is the way it is supposed to be and has anybody else had the same experience and what to do about it.
 
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Old 01-23-23, 04:28 PM
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As to mixing, the instructions are (again on many videos on youtube
So then I have to confirm, did you follow the instructions from the manufacturer or some video?

I have never mixed a bag of mortar that was so dry I could make a ball and toss it in the air!

​​​​​​​Not much can go wrong with that.
Well maybe this time, it sounds like you were short sufficient water to hydrate the materials.

Keep mixing in water a little at a time and blend with the hoe until the mortar has a smooth, workable "buttery" consistency. To test the mix, make a furrow with a hoe. The sides of the furrow should hold their shape without crumbling or sagging.


 
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Old 01-24-23, 06:26 AM
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It sounds like you did not mix the mortar properly. Follow the directions on the package... not a YouTube video. The instructions will tell you how much water to use and you can use a bit more or less depending on the consistency you want, but following the instructions will give you a mortar that works/hardens properly.

When mixing mortar you need to include a rest into your figuring. For example, at first the mix might seem wetter than you want. But over several minutes the water is used to start the chemical process. So, over the first five minutes the mixture will thicken noticeably. Still, it is better to start on the dry side because you can always add more water if needed.

Another thing is you need to have the mortar in place before it's time runs out. If you re-mix or keep working the mortar after it's started to harden it breaks the bonds that make it strong. Those bonds only form once so if you over work the mortar during installation it will never harden properly.
 
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Old 01-25-23, 08:04 AM
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There are many videos on the net and they are almost exactly alike when talkng about doing the dry mud pan. I think you may be right in that i jumped the gun on tiling. Now i am more concerned about maybe i i have exceeded the load limits of the floor. Always something. This bath is on the second floor and has 2x10 joists instead of 2x12. Found that out after i did the shower. Go figure. LOL
 
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Old 01-25-23, 10:30 AM
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Mud beds are more trouble than they are worth. Too many chances for failure.
 
 

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