We have torn out an old fireplace and are going to frame up to install a drywall there instead. We were recommended nail plugs at the construction store because we thought the wall was harder than it was. When we drill, it crumbles in the holes, making them way too large. And the nail plug doesn't have a chance to hold. We've tried drilling with a 5.5 mm drill since the nail plug is 8mm, but it still crumbles and becomes too big. Do you have any good tips on what I should use and how to proceed?
Have you tried drilling at a different distance so you don't hit a joint?
Otherwise, it's likely aerated concrete/Leca, and then you should use screws for it.
However, it feels like it should be brick if there has been a fireplace.
There was brick in the fireplace, but we have torn it down. What is behind one side of the fireplace is part of the chimney stack that was built in 1901. The other side seems to be just concrete, porous as can be.
