Help! Special beading where lime meets concrete?

Mark Devon

New Member
Hi, we bought a house recently in Totnes, Devon, UK, and would love some advice please. Thanks in advance!
It's an old 18th century stone house - a mix of some granite and mostly softer stone - which was covered in waterproof concrete render around 30 years ago.
On one large external wall face we found that the concrete render had cracked from the the third floor down in a narrow strip - perhaps caused by damaged gutter and window frame; and there was noticeable damp on the plaster internally where water had got behind the concrete render and couldn't escape.
Imagine a large square of wall, with a damaged vertical strip down the middle.
We were advised to remove the concrete render in the damaged external strip to allow it to dry, and to re-render that strip with breathable lime; (as well as us replacing all plaster internally on new stud walls).
Many folks have said the old walls like to absorb moisture in winter and dry out in summer.
So far so good: concrete render has just been removed, and we've spent 2 days scraping out between stones - many in v bad state - in prep for repointing and rendering.

But how do we ensure when a pro applies lime render to that vertical strip, that future rain will not go sideways behind the concrete and cause problems with damp internally and loosening the concrete render externally?
We need some kind of beading perhaps on each vertical border, or a slit cut into the wall and something injected into it?
We know that in theory we should go with breathable lime render all over, but a) we don't have the budget or time to remove, repoint and re-render all over; and b) the damp was only in one narrow section and on the rest of the house the concrete render has hung on well0.
If you have an idea how we can create a border so that rain water doesn't go through the lime render and behind the adjacent concrete render, please share your thoughts.
Thank you!