Thanks Kornel and Brent.
We still need to find out what`s the cause of the mold. It started at the crown moulding of the wall next to the neighbor in the next house (in a semi). That could be a possible reason.
We have someone come by and took a quick look and suggest to take out wall section...
Just bought a duplex in Toronto. Previous owner has done some reno to the basement and we recently found out small scale of mold starts growing on the crown moulding on the floor. The basement unit is vacant right now and we have potential tenants coming in every day.
We plan to follow the cmhc...