In reply to Gordonbp:
I'm neither a builder nor a plasterer so take this with a pinch of salt. I researched this a bit a few years back when I started restoring an ancient cottage with rubble built walls. From what I understand it is normal to expect a certain amount of damp in old stone built cottages and part of the render's function is to allow that moisture to breathe out. It is important to use lime rather than modern products which attempt to weatherproof but end up forming a barrier causing the damp to get trapped.
I would have thought (again, non-expert view here) that leaving it to dry for a bit would be sensible if you think it is soaked but ultimately it will always be a bit damp by modern standards so don't get too excited about it.
