greenboard and hardiboard issues

I am remodeling my bathroom and I have installed hardibacker in the tub and shower areas and greenboard everywhere else. I have been told too many different things on how to finish the joint between the hardibacker and the greenboard. Do I use tape and joint compound or do I use fiberglass mesh and thinset?
My next issue is: I am tileing on both the hardibacker and the greenboard. Do I have to use mastic on the greenboard and thinset on the hardibacker? My project is at a stand still until I find out. Thanks

Best advice is to visit our friends at the tile forum, www.johnbridge.com They are really good.


Just for discussion, I would offer that there is not necessarily one right answer. I would use mesh tape and waterproof joint compound. You may be able to use regular tape and joint compound. I would not use thinset.

I believe that for areas not actually in the shower, you can use mastic or thinset on greenboard or hardibacker.

That's my two cents. Check the forum I mentioned for more complete advice.

Thinset will work fine on the junction of the cbu and greenboard. If the seam will be entirely underneath the tile, treat it just like you would a cbu/cbu seam.

Vapor barrier behind the wet areas?

Bob

What waterproofing did you put behind the wet area? Better put a liquid membrane now if you have nothing yet. Redgard and Laticrete 9235 are known to be good.

Thinset is a must in wet areas. Works well everywhere else too. Mastic is an optin in dry areas.

David