We have two en suite bathrooms, either side of the central wall in the
house, and on the roof above is a large Victorian four pot chimney. The
bathrooms were installed around thirty years ago, so the walls are
probably now plasterboard rather than original lath and plaster. Within
each bathroom is a recess, either side of the original chimney breast
(one recess in each bathroom).

Due to failure of the flashing (?) on the chimney, water seems to have
run down the inside of the granite wall until it hit both recesses where
it came through - both recess are tiled. The result is that the
plasterboard has swollen, and there is now a crack (1/8 inch or
thereabouts) all around the external angles of both recesses, although
the tiles themselves are still firmly in place.

The chimney problem is being fixed (not by me!), and the plan is to
allow the plasterboard to dry, scrap out the cracked grout and replace.
Does that sound reasonable, and how long should I wait for the PB to
dry?
--
Graeme