# Tape Hardi Board to 1/2" drywall



## CGallagher (Apr 20, 2010)

Hi,

I am removing sheetrock and adding hardi to concrete basement walls that are prone to take on water. First the bottom 3' of sheetrock was removed and hardi was installed using thinset and tapcon screws. My question is: What is the best way to proceed in taping and floating the hardi to hardi joints and hardi to sheetrock joints? Is there a special trick to combine these are 2 different materials?

Thanks,
Charles


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## pzeiler (Apr 2, 2010)

Hardi to Hardi should be taped with fiber tape and mud the seam with thinset. That's your strongest bond to the Hardi. Or mud the seam first with thinset and imbed the fiber tape in it. In my experience where I am joining hardi to drywall at the top of many shower surround rebuilds or installs I will tape the joint first with fibertape and then float or skim the joint with joint topping....just as you would a normal drywall to drywall seam. Haven't had any issues yet in any installs so long as the 2 substrates are affixed securely to the same framing and there isn't a "seam" in the framing. I also try to leave at least a 1/8" gap between each of these to leave room for mud or thinset to get into the seam and fill the void. Interesting use of hardi. I never thought of it like that but just be careful of mold issues forming behind your hardi now....on the framing/foundation, etc.


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## CGallagher (Apr 20, 2010)

OK, I'm with you so far. I like the fibertape and thinset idea. If the room were to flood again, regular sheetrock tape would peel off and bubble, but the fibertape and thinset would hold. The only problem I see is that I probably couldn't get the hardi to hardi joint smooth enough for the hardi to accept a textured finish. So I could skim coat it with drywall mud to get it nice and even, and probably wet sand it.


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## pzeiler (Apr 2, 2010)

I didn't realize that you were going to finish this wall. I guess I wasn't sure what you were doing next. You could skimcoat the wall and get a smooth enough finish I guess, however if the room does flood again, that's going to most likely screw up your finish also, and cause you to redo it again. Maybe you need to address the flooding issue as your main concern first, then you can finish the room. Is that a possibility? Where's the flooding coming from? Sewer backup or leaking basement walls?


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## CGallagher (Apr 20, 2010)

The home is right next to a bayou. And the basement was never really meant to be livable space. The original builder even installed floor drains to allow water to drain to the bayou. But occaisionally we get hurricanes and flash floods and water pours into the room. It happened twice in the last couple of years. There is no stopping the water from coming through the doors. We are installing backflow devices in the drains, but I doubt they'll be 100% effective. 

Also, water typically doesn't stay in the room more than a couple of hours. The floor drains allow for all the water to flow out once the bayou levels begin to receed. 

The finish is considered collateral damage. As it stands, when the room would get a foot or two of water, the bottom 3' sheetrock would have to be torn out to get rid of mold, reinstalled, retaped, retextured, blah, blah... The Hardi was meant to eliminate the step of removing sheetrock.


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