I recently bought a two-story condo unit. I decided to replace the bathroom exhaust fans upstairs, but when I removed the old fans, I discovered the exhaust duct was not connected to the roof vent: both ducts traveled all the way to the vent and joined at a tee, but there was a six-inch gap between tee and roof vent. Like this:
As you can see, it's a flat concrete roof (I think it's hollow-core slab), and the duct is 4" galvanized. An opening was cut into the concrete for the duct and vent. The duct tape on the tee makes me think it was attached to something before, but when I get my phone in to look straight up, I see this:
The roof vent is flush with the concrete, but off-center, so it is obstructed (only by about half an inch) on one side. It's unclear how the tee ever could have connected, and there's no sign of any missing pieces.
The question is: How do I attach a new exhaust duct to this vent?
I am accessing the space from a 7" by 7" hole in the bathroom wall, which is tiled:
All I can see from the hole is what you see in the first picture; the vent can't be seen directly.
I could use tools to chip away the concrete, but I'd need a tool that can be used one-handed in a confined space without any visibility. (I tried a drill with a masonry bit in the hopes of knocking some chunks off, but it's simply too big and I can't see what I'm doing.) I've thought of using flexible duct taped from the inside, which could work around the obstruction, but would the tape eventually fail from the heat and humidity? I could make a better access hole, perhaps directly underneath, but then I'd have to retile my bathroom ceiling.
Ideally I'd like a solution that doesn't involve roofing work, since then the condo association has to get involved to approve roof work, making it harder to get contractors interested in the job.