Bought my house in august of last year. It's a house from 1961, I had it inspected before buying and the inspector notice that the floor corner of one of the room had a high humidity level, told me to eventually check it out. I tore open the corner of the room, some of the insulation at the bottom was wet. Most of the wood (95%) is in good shape, dry, the corner of the slab seems dry too. I must admit I jumped a foot or two when a saw all the black residue. I doesn't smell, some feels dry to the touch, some a bit humid, I don't know what to make of it....

 

Sure looks like mold. Spray a little hydrogen peroxide on it and see if it foams. If it does, it's mold.

 

It foams......where do I start to tackle this?

 

Remove the tainted material, treat what can't be removed for the mold and then address the water problem that allowed this to happen in the first place before replacing the insulation and wallboard.