Hello! I live in a condo rehab on the top (third) floor. Before I purchased the place, there were a few cracks in the roofing that were repaired. Flat rubber roofing. There have been no noticeable leaking problems since, but in one of my walls, an exposed brick wall, there are three bricks at the top north corner that have been giving off efflorescence. These bricks butt up against a plaster wall, and about an inch to an inch and a half in from these three bricks, the plaster also collects some efflorescence making the paint not stick for that small area.
I believe the efflorescence is coming from the humidity present in the attic space.
Since there is no attic space access (shortcomings of Chicago building codes for rehabs, I suppose), my plan is to get some brick sealant for those bricks and likely a few around them, wait until summer when it's particularly hot and dry, and then seal them off. My worry is that by cutting off that pathway, the efflorescence will just bust on through the plaster even more, creating a worse problem than I have now.
Does anyone have any advise or experience in sealing off interior bricks? In addition to being adjacent to the attic, the brick wall is also an exterior wall to the building. I can also take a photo if that would be helpful to anyone interested in sharing their perspective on what might be the best course of action.
Thanks in advance!