Hardiebacker onto terracotta hollow tile wall - Tile Advice

[Dumbo]

A query about your comment..... the thought i have, is if normal plaster finish walls can only hold about 20kg psm, how can a dot and dabbed only boards hold more? For arguments sake, say the dot dabs made contact with 20% of the area of the boards, that implies that the dot/dab adhesive is over 5 times stronger than plaster, as its covering only a fifth of the area but holding more weight. Is my logic correct?

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You have a good point. Plaster comes away from its background a 20 kg a metre whereas the paper separates from the gypsum core of plaster board at 32 kg a metre but as you point out you do not get a full coverage of the plasterboard when you bond it to the walls and this is probably why the likes of jackoboard ,marmox etc recommend additional mechanical fixings .