Fire caused extensive damage to one side of a duplex at 34127 George Ferguson Way in Abbotsford on Thursday night.
Abbotsford Fire Rescue Service crews were called to the scene at about midnight.
When they arrived, heavy flames were coming from a bedroom window on the east side of the duplex.
Crews quickly brought the blaze under control. No one was home at the time.
Assistant Fire Chief Dave Rivett said although damage was limited to one side of the building, the entire structure is uninhabitable at this time.
He said investigators are still trying to determine the cause.