The one thing new sweeps keep missing with stainless liners

I've been doing this 18 years now, and every time I get a call about a rattling liner, it's the same problem. People forget to account for thermal expansion when they cut those stainless sections. I had a job last month in an old Victorian where the homeowner's nephew installed it and left no gap at the top. By the time I got there the whole thing had buckled up and popped the rain cap clean off. Have you guys found a specific gap measurement that works best for most setups?

2 comments

2 Comments

logan_schmidt2d ago

I read a good piece from a guy up in Maine, he runs a chimney service and swears by a 3/8 inch gap at the top for most stainless liners. He said anything less and you're asking for trouble with the expansion. That jives with what I've seen too, especially on those older houses where the flue tiles are all wobbly. I had a similar call to yours where the guy used a 1/4 inch gap and it still popped the cap off by mid-summer. Do you find the type of stove makes a difference in how much gap you leave?

the_ray2d ago

That Maine guy's advice sounds spot on. I've seen 3/8 inch work best too, it's like the sweet spot for most jobs. The stove type definitely matters though, especially with those newer EPA stoves that run hotter. Had a customer with a Blaze King last year, thing was cooking at 600 degrees on the reg, and even with a 3/8 gap the liner still shifted enough to crack the crown. You ever run into a situation where the stove is so efficient it actually changes the expansion rate, like with those high efficiency gas stoves that run small diameter liners?