A house on Khenipsen Road in Cowichan Bay was completely destroyed by fire on Thursday afternoon.
Another house next door was badly damaged as the fire spread to surrounding trees and then to the home, but is repairable.
Scott Henning, chief at North Cowichan's South End fire hall, said the cause of the blaze was unknown as of Friday morning, and the investigation is continuing.
There were no injuries as a result of the fire.
Henning said it took about five hours to completely extinguish the blaze, with four fire departments involved.