The point of mortar under the hardibacker is to ensure even bedding and good support of the hardibacker.
Roofing nails with thinset mortar.
A rapid setting and hardening cement to create concrete and mortar for all building repair and maintenance work extra rapid sets in just 30 minutes and is suitable for concrete drives and paths concrete steps fixing fence posts railings and copings.
Of a little known fact but most cement board manufacturers want fiberglass alkaline resistant mesh tape embedded in thinset mortar over the backer board seams.
But this doesn t stop people from trying to use ring shank nails.
Most cement board manufacturers require galvanized roofing nails or cement board screws.
Apr 15 2016 yes thinset will bond to plywood however the thinset under a backer board is really just a filler that prevents hollow gaps that can flex when walked on the roofing nails are doing the actual holding if you want a good bond which is not needed look for a modified thinset approved for setting tile over plywood or mix liquid.
You ll still need to screw it down with deck screws 1 or 1 1 4 and avoid the joists or nail it down with roofing nails.
1 inch corrosion resistant roofing nails 1 inch self drilling corrosion resistant screws drill sponge use a sponge to wet down the backer board before applying thin set above the backer board 2 inch wide alkali resistant fiberglass joint tap setting materials square notch trowel thin set mortar.
Use nails or screws as temporary spacers to create a 1 8 in.
When you squeeze the thin set mortar into this gap it will lock the two sheets together and strengthen the seam.
It s not really there to stick it down although it doesn t hurt.
If special screws aren t available attach the cement board with 1 1 2 in.
Gap between sheets of cement board.
While nailing the cement board down the spacing should be approximately 8 inches apart.