My Cleveland Ohio home was built in the 20s. Original fireplace has a brick chimney (fireplace has been converted to gas) Home has a large third floor attic that was finished with drywall and carpet by the previous owner. One day I noticed surface mold and heavy moisture in a corner on the 3rd floor (Paint so saturated it was practically falling off the drywall). The chimney is located right on the other side of the leak, so I had the flashing around the chimney at the exterior roofline repaired. I removed the damaged drywall to discover the brick chimney was totally flush with the interior wall and had just been smoothed out with plaster, and drywall installed on either side of the edges of the brick chimney. It looks like someone had previously patched up parts of the brick masonry with some type of grout/concrete. Now I'm unsure if the flashing repair was the cause of the leak or if there is water coming in through the mortar/bricks. How can I determine whether or not the leak is still present? Any tips on creating more of a barrier between the interior wall and the chimney?