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Discussion Starter · #1 ·
Hi.

I am remodeling my bathroom. I am ready to start tiling tub and shower surrounding walls. Yesterday I applied the RedGard Waterproofing membrane over Durock Cement boards. Then I checked the instructions on the premixed stone, porcelain and ceramic tile thin-set mortar which I am going to use to put tiles and found that it says: "Do not use over waterproofing membrane."
I already opened the 3.5-gallons mortar container and used a little of it so I can't return it. Plus I don't know what else I can use instead. I used the same mortar last year for similar project but without RedGard and it worked fine for me.
My question is why I can't use thin-set mortar over RedGard waterproofing membrane?


Thks.
 

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Then I checked the instructions on the premixed stone, porcelain and ceramic tile thin-set mortar...

My question is why I can't use thin-set mortar over RedGard waterproofing membrane?..
You can, but not the premixed stuff. What specific product do you have?

You don't want to use the premixed stuff in a shower or wet area.
 

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Discussion Starter · #3 ·
I have the "Premixed Stone, Porcelain and Ceramic Tile Thin-Set Mortar" produced my SimpleSet.
It was recommended to me by Home Depot employee. I used it last year in my son's bathroom for tub surrounding wall tiles. It was easy to use and no problems so far.
Why can't I use the premixed stuff in a shower? What else can I use to tile shower and tub surrounding walls built from Durock Cement boards covered with RedGard?
My options are pretty much limited to stuff sold my HD. I also have a tile shop in my area. I'll check with them, but I don't really trust them. Unfortunately, neither I can't trust HD people.

Thanks.
 

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Discussion Starter · #5 ·
Thanks a lot for the thread.
This is the same so called "thin-set mortar" I used last year for my son's bathroom and was planning to use for my bathroom.
My two questions still remain:
1. Why, in general, can't I use this "thin-set mortar" over the redgard membrane?
2. What is the best choice for me to use for tub and shower surround walls tiling? HD sells few thin-set mortars, but which one to select? I don't want to ask HD guys anymore as they not just useless, but also can send me to a wrong costly direction.

Thanks.
 

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1. From what I have read, the premixed thinset does not dry out to form a good adhesive bond when applied over/under a non-permeable membrane like Redguard or the Kerdi-band products. The dry mix (where you add the water on-site) does.

2. The Versabond fortified thinset is a good product at $13-$16 per 50 lb bag, and will work fine for your application. The more expensive dry mix thinsets provide more flexibility to withstand expansion / contraction experienced with freeze/thaw cycles, e.g. in outdoor applications.

Good luck.
 

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Premixed mortar, don't use it, especially for tile in a wet area. Take it back, purchase a good modified thinset "dry mix" in the bag along with a paddle mixer for an electric drill. Mix it with the appropriate amount of water to the consistency of peanut butter. Check the working time for your mortar, and apply it with the appropriate thinset trowel for the tile your installing. Easy!
 

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Red Gard Mix???

I have read a few posts where the Red Gard was mixed with some parts water...Am about to apply on shower walls - do i need to mix Red Gard before i appy?
 

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sejmid please go back and add your own post.
No way to keep track of who's talking to who.
 

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Hi.

I am remodeling my bathroom. I am ready to start tiling tub and shower surrounding walls. Yesterday I applied the RedGard Waterproofing membrane over Durock Cement boards. Then I checked the instructions on the premixed stone, porcelain and ceramic tile thin-set mortar which I am going to use to put tiles and found that it says: "Do not use over waterproofing membrane."
I already opened the 3.5-gallons mortar container and used a little of it so I can't return it. Plus I don't know what else I can use instead. I used the same mortar last year for similar project but without RedGard and it worked fine for me.
My question is why I can't use thin-set mortar over RedGard waterproofing membrane?


Thks.
I applied tile using thinset mortar to a surface I had covered with red guard just for a little extra protection. It’s been almost 2 weeks and the mortar isn’t set yet. That’s why.
 

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My question is why I can't use thin-set mortar over RedGard waterproofing membrane?
The problem is you don't understand how your materials work. You can use a SETTING material. You cannot use a DRYING material. Any premixed material (thinset, grout, drywall joint compound) must dry to get hard. That is not true with powdered thinsets and grouts. They get hard chemically and do not need to dry. Technically they can stay wet forever (think of concrete pylons for bridges in water.)

In fact, you should not even use premixed thinset with large tiles in any application regardless of waterproofing.

What you are doing is trapping the thinset in between a waterproof barrier and a porcelain (probably) tile through which water also cannot penetrate. So obviously it can't dry.

Home Depot has tons and tons of powder thinset (setting type thinset) options. However over a waterproof substrate (such as Kerdi or RedGard) Lowes has one that I would recommend. There are better ones that your tile store probably sells, but this will be fine.

 

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I applied tile using thinset mortar to a surface I had covered with red guard just for a little extra protection. It’s been almost 2 weeks and the mortar isn’t set yet. That’s why.
You also don't understand the difference between setting and drying. If you used a powder thinset that you mixed with water, then it will be set within 24 hours (getting harder as more time goes by). If you use a premixed drying type "mortar", then it might not ever dry and therefore get hard (espeically if you've grouted). Or maybe if you wait a couple months before grouting it might start to dry.
 

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Yeah, but the thing is, these threads get looked at. Someone searched for something, found a 10 year old thread, and wrote to it. So it's really not dead. This is all part of an online database that people can look at for years. Adding new info isn't bad.
 
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