Fired at the muzzle, a representative 12ga Slug load (28.3 g, SLUG, 500 m/s) reaches roughly 376 mm (14.8 inches) into drywall (gypsum). That is enough to defeat a typical barrier of this material — treat anything behind it as exposed.
About Drywall (Gypsum)
One sheet of interior drywall is ~13 mm; a wall is two sheets and a gap.