patching walls

[Janela]

Hello
I am about to redecorate (limewash ceiling and re-clay-paint walls) and am looking at my options to patch damage to the walls.
This was one of my first attempts at plastering about 15 yrs ago and I made quite a few errors (I now think/realise) but also we have had a leak around the chimney stack which has taken years to resolve and have a concrete slab (which sadly has to stay financially and practically).

The first pics show the area around the chimney - just the top layer of plaster has detatched (I made the mistake of trying to plaster when it was 40°C outside and it just dried too quick.) ALTHOUGH there are quite a few patches where it is blown, it is holding solid, I believe, due to the horse hair in the plaster.
These little bits I thought to use modern filler which can be sanded and painted over.

Around the doorway I plastered too deep with Non -hydraulic lime and the concrete slab has created damp in the walls at this point. For this area I am wondering what to do!! If I start removing until I get to solid plaster I fear it will be a lot, do I patch with hydraulic or non hydraulic? . I'm not really ready to start replastering a huge area as I have too much else to do at the moment, also I'm hoping the rest will hold and I can get away with a small repair!

I also have not worked out how to patch lime and get a smooth joint that won't show once painted - ?? where I have tried I am left with the rough effect of the sand in the plaster at the joint.

All thoughts would be welcome please.

 

[a twig]

Been a while since I’ve done any patching but from memory this is roughly what I did.

Cut back the edges of the existing plaster using a knife or similar ensuring that the edges of the patch are cut square or with a slight undercut to provide a key for the new mortar, and eliminate the need for feathering.

Damp down the area and apply the repair plaster render in thin coats taking care to ensure that it is well pushed in beneath the square/undercut edges of existing plaster.

Apply the final coat with a neat butt joint between the old and new and with a slight bulge in the middle of the patch so that the final consolidation will create a flat patch, flush with the surrounding render.

Do not feather the edge of the patch over the surrounding plaster otherwise you end up with the sandy issues you describe.

Finally as the plaster is starting to go off push back and consolidate the final coat of a patch with a float.

 

[Janela]

Thank you very much, i hadn't thought about cutting the edges to avoid feathering in- makes perfect sense when you've been told.