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Unread 10-24-2015, 11:51 AM   #1
South land Tile
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Priming hardi backer before applying kerdi

Im one of those guys that prefer installing hardi backer but as is a commonly noted problem the thirstyness of the stuff makes hanging kerdi a pain even with sponging it before troweling thinset on. Somwhere on the forum I remember somebody mentioning in a post the possibility of priming the hardi with something like quickcrete primer or something like unto it I called laticrete tech services yesterday and asked about using nxt primer and then hanging kerdi with their 317 thinset and got a absolute no but I guess I'd like to know why it wouldn't work.
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Unread 10-24-2015, 04:09 PM   #2
Jim Cordes
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My vote is to stop using the hardi. first off other then it being thirsty it can also get moldy in a wet environment(which doesnt matter if your using Kerdi).. cement based CBU's dont and they also don't have a problem with being thristy either.

I will assume the reason you prefer hardi is becuase it is flat? Now if thats what you want. It is perfectly fine to just use drywall under the kerdi as per warranty.

If you are worried about mold and want to over build it with something that cannot feed mold..then use regular cement board. If your wanting flat and ease of installation then use drywall.

There is really no advantage to using Hardi under Kerdi. and as you have discovered there are disadvantages.
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Unread 10-24-2015, 04:21 PM   #3
jadnashua
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Hardie is thirsty enough such that it can benefit from a garden sprayer. As long as there is no liquid water on the stuff, you have not gotten things too wet.
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Unread 10-24-2015, 04:57 PM   #4
Kman
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If I was going to use Redgard over Hardi, I would prime it with a diluted mixture of four parts water to one part Redgard. I think that's the ration Custom recommends for priming.

But I agree with Jim that sheetrock makes good substrate for Kerdi.
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Unread 10-25-2015, 09:48 AM   #5
tilemanct
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Every shower repair I do that has Hardie as the backer is a mold farm. For some reason this stuff sucks up the water like there's no tomorrow. I agree with Jim's advice.
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Unread 10-25-2015, 11:51 AM   #6
Ron
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I won't use it. One time I put it in a vestibule in a store. The panels were bent from sagging on the pallet. When I installed it on perfect framing there were high and low areas between the studs. Hate to screw into it. Hate cutting it; gotta score it many times with the T-headed cutter. It delaminates if you gotta break narrow pieces AND the moisture-sucking problem.

Sorry, but I just hate it.
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Unread 10-25-2015, 12:13 PM   #7
alex.h
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The primer we are speking of?

Does it contains latex/polymers? Kerdi and polymers is a no.

Also laticrete sells their own menbrane makes sence they would not recoment their producs to apply some one else's
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Unread 10-25-2015, 06:36 PM   #8
Dan Kramer
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Laticrete doesn't warranty any of their products in conjunction with Schluter's stuff. At least thats what a Lati guy told me.

If you use Hardi, do as Jim suggested and saturate the board with a pump type lawn sprayer before spreading thinset. Just make sure there is no "standing" water before application of thinset.

Use sheetrock!
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