How do you tape Hardie board joints?
Considering this, should you tape cement board joints?
The thinset and mesh tape are to strengthen the seams. If you are going to tile over the cement board, you should tape the seams. If you just want to leave the corners untreated that will probably be fine, because that seam won't split the center of a tile.
Secondly, does Hardie board need waterproofing? Passing ANSI 118.10 for waterproofness, HardieBacker® 500 Waterproof Cement Board protects tile installations and wall cavities from moisture penetration, eliminating the need to spend extra time applying waterproof coating across the entire surface area of your wall project.
Beside this, do you need to tape drywall behind tile?
If you're working with new drywall, there's no need to tape the drywall joints. Seal the walls with a skim coat and let it dry thoroughly. Thoroughly vacuum the area and give the wall a once-over with a damp sponge or cleaning cloth. Allow the area to thoroughly dry before beginning tile installation.
Do you need to seal Hardibacker before tiling?
To Seal or Not To Seal Contrary to popular thought, tile and grout are not waterproof, and some moisture will penetrate even if sealant is used. If you decide to go this route, no sealant will need to be applied on top of the backerboard, as this could trap moisture between the two layers of waterproofing.