Insulation and Vapor Barrier behind Hardi Hydrodefense

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DIYguy88

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Hello everyone! I have been lurking around for a bit and been finding conflicting info on this subject so I figured I'd get confirmation. I am attempting to build a stand up shower and would like to use Hardi Hydrodefense for the walls and ceiling of the shower. I would also be using a gold bond purple xp for the remaining walls and a kerdiboard pan with kerdi waterproof on top of the hardi for extra defense. I also may put on redguard as well just to bulletproof things. My questions are:
1. I've read conflicting info about redguard and thinset not playing nice on hardi with tile. Is that true?
2. My side wall is a concrete block wall in the basement. Currently the only insulation is around the header. Should I put 1inch rigid behind the studs and roll insulation between studs topped with a plastic sheet for vapor barrier? I've also seen conflicting info about putting a vapor barrier behind hardi.
3. Should there have been insulation behind this wall since it is a 95% finished basement along the foundation in Michigan? It gets down to 50-55 in the winter. It is a walkout raised ranch and I feel the didn't insulate the walls when they finished it.

Sorry for the long winded question. This forum and its members are amazing and I'm learning alot! Thanks for all the work you guys do!

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Tuttles Revenge

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I have no guidance/advice on shower/tile product.. but it looks like that's just bare untreated lumber on the concrete floor too.
 

DIYguy88

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I have no guidance/advice on shower/tile product.. but it looks like that's just bare untreated lumber on the concrete floor too.
Yes it is! I'm replacing that sil with treated. I couldn't believe some of the things the previous owner did to this house that wouldn't meet code!
 

jadnashua

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1. Hardiebacker is EXTREMELY thirsty, and if you don't follow the instructions carefully, doesn't work well. The instructions call for you to first dilute the Redgard and use it as a primer, then once that dries, apply the normal two coats so it's a lot of extra work.
2. Insulation won't hurt but you DO NOT want multiple vapor barriers...IOW, if you're going to use Redgard on the inside, you don't want another layer behind it.
3. It wouldn't hurt to insulate the walls to the rest of the basement if you aren't going to fully heat it.

But, if you're using Kerdi...do it all with Kerdi and forget the Redgard. Personally, I'd also forget the Hardiebacker as it's harder to cover it with Kerdi...you CAN use it if you insist, but a properly made Kerdi shower is tested, certified, and approved to be made over plain drywall because it works...the drywall will not be damaged since it won't get wet. The drywall comes in bigger sheets, fewer seams, cheaper, lighter, and easier to cut and works just fine. If you haven't read their shower manual, do that and watch some of their videos. It's important to wipe the surface with a wet sponge prior to spreading the thinset or the substrate can suck too much moisture out of the mortar, making it stiffer, and harder to get things to work right. Thinset does NOT stick to Kerdi...it flows around the fibers, then cures, locking it in place. If it's not properly mixed, the thinset doesn't hold much since it doesn't bond to the surface, only by flowing around the fleece, sort of like pouring wax on fabric, then it solidifies. Kerdi gets its watertight seams by close contact of the fleece between the two sheets, so it must flow around the fleece to work and lock things in place.

Check out www.johbnbridge.com for help with building your tiled shower and www.schluter.com for help with Kerdi. Read and study any installation instructions to help you understand what's required to make it all work. John Bridge's site has numerous pro tilers on it and a lot of traffic and resources for study and help.
 
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