Here is a thumbnail outline of the criteria for Hoarding Disorder (and all three must be present even to a minimal degree):
Excessive accumulation and failure to discard proportionately (things and/or animals).
Activities of daily life are impaired by spaces which cannot be used for the intended purpose.
Distress or impairment in functioning to the person hoarding or others. Even if “others” don’t know about the hoard, they would have reason to be concerned.