Visited a 150-year-old house in Portland and noticed something weird about their flue

I was doing a routine sweep at this old Victorian place last Tuesday, and the homeowner mentioned they'd been having draft issues. I got up on the roof and saw the clay liner had this strange spiral pattern inside it, like someone carved grooves into the terracotta. Turns out the original installer did that on purpose back in the 1870s to help with smoke draw, which I never heard of before. The flue was still in decent shape after all these years, just needed a good brushing and a new cap. It made me realize how much thought went into these old systems compared to today's prefab stuff. Has anyone else run into old flue designs that surprised you?

2 comments

2 Comments

umaprice1mo ago

Those old timers must have had nothing but time on their hands to be hand carving spiral grooves into clay liners. Probably figured it was worth the extra work to keep the smoke moving instead of just slapping in whatever Home Depot was selling back in 1870 whatever that was. I can only imagine what that chimney sweep thought when he first saw it, probably thought he was losing his marbles or someone was playing a prank on him. At least the homeowner got a good story out of it and a flue that outlasted most modern houses.

wren9761mo ago

Whoa, thats actually wild. I mean Ive seen some weird old flue tricks before but spiral grooves in the clay liner is a new one to me. Did the homeowner say if the grooves were cut by hand or stamped into the clay before firing? That must have taken forever to do by hand back then. Also did you notice if the spiral was continuous all the way down or just in certain spots? I feel like that detail could tell you a lot about how much they were trying to compensate for chimney height or wind patterns. Really makes you wonder what other hidden engineering is sitting behind plaster and lath in those old places.