I have a few apparently cast-iron chimneys bedded in concrete. They have no hats on them. I’m not sure how the fireplaces were blocked off but it feels solid, as if they bricked them shut and plastered over it.

Isn’t this a bad idea? They don’t seem to be filling up with rainwater yet it rains quite heavily. I assume the fireplaces have been blocked off for over a decade at least. There must be quite an ecosystem of creepy crawlies going on in there.

So what if I want to open the fireplace back up and install a boiler, sewer vent, wood stove, kitchen range hood, or ventilation system? Can they be restored or must they just be treated as wasted dead space?