Does water damaged plasterboard need to be replaced?

Generally yes, the board should be removed and replaced with an equivalent Gyproc product to maintain the original performance criteria.

This would certainly be the case where boards can be seen to be ‘bowed’, suffering with mould growth or where paper de-lamination has occurred. Other instances such as surface wetting, which may dry out relatively quickly, could still develop water stains or mould requiring remedial treatment/action at a later stage of the project.