I have a newer home that the builder put a concrete vault in. It is basically the porch that was dug out fully to make a room under it with a steel security door. The concrete porch is the ceiling. There are vents into the room so I can keep circulation in it. I would like to finish it off without taking up much space so I can use it as secure storage. I don't need much insulation, just enough to help keep the temperature somewhat steady as I would like to store some art and guns in there. My plan is to prep the outside walls and ceiling by painting them with DryLoc and then finishing them.
One thought is to do 2x2 walls with foam insulation glued to the concrete and then putting either sheet rock or some kind of paneling over it.
Another thought was some kind of Foam backed OSB and securing it directly to the concrete with the foam against the concrete.
I am pretty much at a loss for what to do on the ceiling.
I am not overly concerned about electrical as I will only need one or two outlets at the most and I could do them as surface mounts.
Any suggestions or ideas?