Shower, tiles on plasterboard w/no tanking

[hvendlor]

I recently discovered our bath/shower has been tiles directly onto plasterboard with no tanking solution.

Is there something I can rub over that will soak into the grout to make it (more)waterproof?

...and how long before the plasterboard turns to mush?

 

[jefoss]

chances are nothing will happen, you can however use a grout sealant to help your cause a little better, any good (or bad) tile store stocks them.