Ran across a stat about creosote and nearly dropped my brush

I was reading through some old chimney service manuals I picked up at an estate sale last spring. Buried in there was a fact that blew my mind. Apparently creosote buildup can hit an inch thick in just one heating season if you're burning unseasoned softwood. I always knew wet wood was bad but never realized it was that aggressive. The book was from 1987 and published by the Chimney Safety Institute of America. Makes me want to double check every customer's wood supply before I even start sweeping. Has anyone else run into surprising numbers like that in old manuals or was I just lucky to find this one?

2 comments

2 Comments

allen.quinn25d ago

lol I gotta push back on this a little. I mean yeah the stat is technically true if you're burning nothing but soaking wet pine in a cold chimney all season. But an inch thick in one year? That's more of a worst case nightmare scenario than something most sweeps actually see. I've been doing this for a while and even the worst junk wood I've run into didn't pile on that fast unless the flue was completely screwed up. Also those old manuals from the 80s were great but sometimes they'd exaggerate to scare people into cleaning more often. I'd rather trust what I see in the actual flue than a decades old book. Not saying wet wood ain't bad, just that stat feels a little overblown for real world work lol.

robinson.quinn25d ago

Yeah I've seen it happen but it's usually a perfect storm thing. Cold chimney on an exterior wall, damp softwood, and someone running the stove low and slow all winter. That combo will lay down creosote like nobody's business. I tell customers it's not just about the wood being seasoned, it's about keeping the flue hot enough to keep the smoke rising fast. If both those things line up wrong you can definitely get a scary amount of buildup in one season.