What is my interior wall made of?

[bomm]

I personally find that it's easier to get a screw to hold well in lightweight concrete if you DON'T drill and plug but choose a fairly coarse-threaded, slightly longer screw and just screw it directly into the concrete. It grips and holds firmly, but you shouldn't loosen the screw and re-tighten it in the same hole multiple times as the lightweight concrete can easily crumble.

 

[StevieGee]

Drill with a bit that is half a mm smaller than recommended for the plug. Use nylon plug. Do not overtighten! If there is plaster outside the lightweight concrete, it can be difficult to insert the plug if you have drilled with a smaller bit. In that case, you can drill slightly larger in the outer part (the plaster).. There are special screws with very deep threads, never tried these as they are extremely expensive. There are also triangular plugs but they don't work well if there is plaster outside.

 

[A-Man_08]

Use the right plug for the purpose, there are plugs intended for leca and lightweight concrete.