Soft line mortar?

[NineMaidens]

Hi all, new here and would value some opinions!!

I have an old granite house. We noticed damp in the walls and are removing the render from the interior walls in one of our 1st floor rooms. Under the render is the stone wall and lime mortar but the lime mortar is very soft on places. I can scrape it out with a trowel. We are planning on re-pointing it but obviously don't want to point over soft mortar.

Does anyone have any thoughts? Advice?

 

[mardinor]

Stop scraping. Lime mortar is soft.

 

[Kearn]

Confused. You don’t point internally, stone should be plastered.

Lime is soft, it’s the sacrificial element in an old wall. Why are you scraping it?

If the wall was wet, then the lime will be softer than usual.

Why was the wall wet? What was the plaster you have removed?

If you were needing to repoint, then you don’t point on top of pointing, you rake out a depth accordingly based on width of joints so the mortar has an ability to key in.

But for internal plastering, a small indentation between stones will help with a physical key, as long as it isn’t more than about 5-10mm deep.

 

[aockenden]

I agree that plastering over the interior walls is the better option, but if you are committed to keeping it exposed internally and simply repointing, then you'll want to rake-out all the old lime from the joints and then repoint all the joints across the whole wall using an appropriate lime mortar in one go so it's all a contiguous, gelled-in capillary network that can effectively redistribute moisture within itself. And also the finishing will look way better if it's all laid across the whole wall and then churn-brushed together all at once.