The walls in the bedroom are falling apart..,.,why?

When we moved in the room had cracks inte wall looks like it was painted over. The home was built in 1929; The cracks eventually became hole. The material the walls were made of was not drywall. I looked likjethick cardboard...the material used on the bottom of a dresser. Does anyone know what this stuff is and if it is up to codefor today.