Personally I wouldn't bother with hardi. Just regular plasterboard and tank the wet area. You want waterproof not water resistant.
http://www.screwfix.com/p/mapei-shower-waterproofing-kit/78484?_requestid=210153
hardie isn't waterproof. It just doesn't degrade when wet. Tank it. Id choose waterproof over water resistant in a shower every time.
How long you been tiling mate ?
12 years and you say hardie board isn't waterproof ?12 years.
It's moisture resistant. It's not waterproof. I'm sure you do cracking work fella, I'm not here to criticise your methods of working. But for an extra £60 on an install (less the expense of the cement board so negligible) I'd rather offer my clients a completely waterproof shower area/wet room.12 years and you say hardie board isn't waterproof ?
https://www.jameshardie.com/products/hardiebacker-cement-board
have a read, you might be surprised lol
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