Help Needed Repairing Old External Lime Render on 18th Century Mansion

[nmok1992]

Hi,

Any advice would be much appreciated, as I really want to do justice to the building and not ruin it with modern products.

I bought a house recently - 18th century building in france. The previous owners did next to little maintenance of the property and let it rot basically. I see it as a life project for me, I don't have the funds to do it all at once, but I'm dedicated to doing it right and bit by bit over time. All my funds for now are going to other key areas like fixing the roof and collapsing ceilings, so I am trying to patch up the render for now while the scaffolding is up.

I did a plastering course and did work a little with external pure lime render, but that didn't include anything on patching.
I 100% know this house needs plaster fully removed and reapplied. But I can't afford that at the moment and that would need a real professional. I am hoping to do what I can for now and get someone in in a few years time.

Does anyone have advice on any of the the following:
1) Skimming over old lime plaster that hasn't gone right back to the bricks yet

2) It said on Toupret, and I called to ask, that some of their external filler works and is breathable on lime render. Even for skim coats. But I looked at the ingredients and it contains cement - that scares me as I was told any cement is bad on these old buildings

3) How easy is fully cured, old lime render to remove if I decide maybe to just remove it all and let it breath until I can afford to redo or leave it with exposed stone/brick and repoint. How would I also then protect the exposed stone/brick?

4) Previous owners patched up before with a concrete lime mix (I tested it by knocking and with vinegar - that trick works really well). Should I remove these concrete patches? Or if they are only small it won't be too much of an issue? Will removing the concrete damage the old stone/brick underneath?

5) Almost the whole back is covered in what I discovered is a fungus of sorts. I can kill it with external cleaning solution. If that is growing to such an extent though, does that mean the whole thing is failing or just cleaning and killing it off will be fine.

Thank you in advance for any help you can give me. I take caring for the history of this house really important, and I don't want to hurt it further given how it has been treated in the past.

 

[malcolm]

Lime is brilliant for patching up. Just chip off the loose stuff to get back to a good starting point. The 5L garden sprayers are very handy - spray the surface and existing lime, wait 5 seconds for everything to become completely dry as if you hadn't sprayed it at all, spray again and repeat until it takes a couple of minutes for everything to dry. Then the wall is saturated and you can safely put lime render on without it having all the water sucked out of it.

Anything with cement in the ingredients is bad. I tend to mix my own render using lime and local sharp sands. Worth a test piece if you do that to make sure it works and get the mix right. Normally 2:5 sand to lime for render will work but it depends on the sand. A small previous repair in cement shouldn't cause too much of a problem so long as the wall can dry around it.

Fungus or mould tends to grow on waterproof surfaces that attract condensation or surfaces that are constantly damp. Do you have a modern waterproof paint on the render?

Worth posting lots of photos for someone to try a better guess.