Repair part of the wall that is a chimney

[madcarpenter]

Hello,

Just finished sanding the floor in one of the rooms and when I removed the skirting against one wall (which is the chimney breast), it was very brittle or whatever you might say behind it, so some plaster came off (the skirting was nailed). Now that I'm done with sanding, I want to put a skirting back there, but I think I want to fix this first, mostly because it will make it easier to attach the skirting. Tips would be greatly appreciated.

I've looked at repair mortar, but I'm a bit unsure if that's the right way to go:
https://www.bauhaus.se/lagningsbruk#go-to-description

 

[jonaserik]

No response yet. Looks like lightweight concrete (a little porous), you can repair it with repair mortar, remember to wet the wall before so it doesn't dry too quickly, otherwise it won't hold and can become like a cake.

 

[madcarpenter]

I'm conducting a test with lagningsbruk, I'll get back with the results!