Plasterboard coming adrift from outer wall

[Big-D]

In the bathroom in our 4 yr old house, the plasterboard wall along the length of the bath/shower is coming away from the outer stone wall.
There is a long crack/gap opening at the join between wall and ceiling.
Pressing a hand on the wall, you can see the gap wideing/flexing.
Is there an easy/direct way to fix this, or will the whole plasterboard need to be removed - along with the 4'x4' mirror and bath?!

Can anyone say if this defect is likely to come under the NHBC scheme?

Any advice appreciated.

 

[^woody^]

It may come under the Buildmark warranty, but you will have to argue that the plasterboard is an integral part of the external load-bearing walls or part of the internal "wet-applied plaster". The Buildmark terms are vague on your cover but specific on the NHBC's rights.

In any case the NHBC will try and dodge their obligations more than the Artful Dodger, dodging on the dodgems eating Jammie Dodgers.

You can drill some 10mm holes and pump some special expanding foam which is used to fix these boards in the first place. I forget the actual product name, I'll have a look.