there Is a diference between vapor barrier and water proof redgaurd waterproof well maybe not if you only apply 1 coat? Wrong. Taken from CBP redgaurd tech sheet.: Redgard can be used as a slab-on-grade moisture vapor barrier under all types of floor coverings. Dennis: always go direct to the product tech spec( as you did) never fight with CA inspectors :). Ditra has been tested for California.exceeds both vapor perm and is VOC compliant theres many better products regardless and sounds like youve found one that will be fine.. DITRA and DITRA-XL were evaluated according to the "Standard Method for the Testing and Evaluation of Volatile Organic Chemical Emissions from Indoor Sources Using Environmental Chambers, Version 1.1" for California Specification 01350 and found to comply with the VOC requirements. California Specification 01350 is referenced by various green building standards and rating systems.

I have been doing research on how to properly build a steam shower in residential home. Currently my shower floor tile cracked, water leaked, so I am really want to do it right this time around. I will hire contractor to do this. I have been reading about Schluter membrane, but it is only for vapor carrier. What about water barrier? I read that we can only do one or another. I also read that vapor barrier is not designed for running water, then what will happen to vapor barrier if the tile cracked and water (not vapor) got it? Better to have double protection. My question is can I can both vapor and water barrier at the same time? How to do it? DO I apply REDGARD over Schluter? But I read it could result in mold issue in layers in between.

Before the vapor barrier was installed everything should have been cleaned and prepped before that.

Thanks guys for all your replies. To give you more context this is a 1964 house, so not a new build. As for climate, I live in southern Indiana. I do have a sum-pump installed with french drain installed all around the parameter of the house inside. Basement is about 1000sqrf and it is all cinder-block and the outside of the house is all brick if that makes a difference. The block seems to sweat and if there is hard rain it seems to get moist in some spots but the block seems to keep mostly dry even during the harshest of weather. I did paint the cinder-block with Drylok. I the thing i want to understand is if it is even worthwhile to install foam boards. My basement seems to stay cool in the summer and warm in the winter. So I'm wondering if I install the foam board will that help with heating and cooling? The way I understand insulation is that it should keep "inside temperature inside and outside temperature outside". So even though my basement keeps cool/warm right now, by installing insulation will it reduce the work load of my furnace and/or A/C resulting in lower heating and cooling cost Worthy, you say to apply the adhesive horizontally, is that with vapor barrier being in place? because without vapor barrier shouldn't I apply the adhesive vertically so any moisture can run down? Dan1888, Why do you say that you hope i have vapor barrier installed under the floor?