Hardie Backerboard Installation

[simon71]

Are the boards on the floor or the walls?
What type of boards are they?
Are the boards in a wet area and forming part of a tanking system?

The answers to these questions will determine what type of taping is required if any.

I think that if you tile over boards that you know (or should have known) must be taped, but haven't been, then this will be your responsibility.
If you are asking on a division of work (and payment) basis then I would think that taping of the board joints should be part of the boarding process (costing). If I quote for tiling only then I am not expecting to be building/finishing/rectifying the walls/floor as well in that price.

The boards are on the wall in a small Ensuite approx 1.2mtx2.5mtr, shower area/tray 1.2x.800. The boards hadn't been staggered.
I have never taped joints to date, only filled with Silicon if the joints were bigger than 2mm, or I had quoted for tanking. When I gave the estimate the room hadn't been built as this was part of the job spec for the builders who were doing the loft conversion.