The investigation into the blaze at 308 John Street was led by the South Bruce OPP, OPP Forensic Identification Unit and Ontario Fire Marshall.
It resulted in the accused, a 26-year old male of Brockton, being charged with arson.
He is set to appear before a Walkerton court February 8th to answer to the charge.
The building is operated by Bruce County housing.
The fire resulted in 20 tenants being taken to a community where where the county worked with its partners to find shelter and other needs.