Worried removing sand cement render inside will/has destabilised thin points in the facade

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This post is pretty much what it says on the tin. At the moment, we're visiting my relative who owns this house. There are damp problems all over and we wanted to remove the sand cement render that had been used on the inside walls of the house.

Cutting to the chase, my husband was working on the space below the window in this photo. He was using a hammer drill/breaker that delivers 8J of impact and it was going fairly quickly. I noticed that the stone must be only one course thick under the window and asked him to stop. I'm very worried about destabilising the facade by removing the sand cement render. If we remove the render, this area under the window may only be held together by lime mortar placed between the stones when we had the facade repointed.

Does anyone have experience removing thick sand cement from such a thin wall? Is it possible we've already weakened this wall structurally by removing what we have already? What do we do if we have? Basically, do we have a future emergency, a current emergency, no emergency?

 

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close up – we stopped after revealing part of one stone but taking off a large area of the top layer of sand cement

 

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p.s. if I've had a panic about nothing, please let me know, as I'm still in panic mode and I'd really like to stop

 

[aockenden]

With that much cement still coating the stones I doubt anything will be going anywhere. Whenever I’m removing cement render in more delicate / unstable areas I usually do it with a hand chisel and hammer and go very slow. Probably starting from the top down. If it was standing before the render went on then it should be able to stand after the render comes off, you just need to get it off carefully.

 

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Thanks for your reply! I went out with the dog and cleared my head. I feel better about it, and your comment was the nail in the coffin for the anxiety I was feeling.

That's super interesting about your technique. I guess the way to tackle these walls is probably to do the thicker wall areas first with the base coats of lime, then remove the diagonal window areas and do those, then do under the window sills last. All top to bottom.

I ended up calling a structural engineer and will have a chat with them as well. There are other things I need their advice on anyway.

I still feel incredibly nervous about having just one course of stone under the windows. I wonder how on earth I'm going to insulate that area. I can't use anything that could destabilise that area of stone. Bit of a nightmare, but what can you do?