Changing chimney pipe size

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New Member
Jun 17, 2023
I recently bought a cabin with a wood stove and in order to get a wett certificate I need to change the chimney pipe. Currently it's 8 inches and I need to reduce to 6 inches. My question is, for the smaller pipe will I also need to change the flashing and/or reduce the size of the hole cut into the roof. Or can the larger flashing accommodate the smaller pipe. Is there an adapter for this?


Full Time RVer
Staff member
Dec 2, 2008
Wherever we're parked
IMHO, I think you can leave the flashing where it is. After the smaller chimney is installed, you will need a larger storm collar to cover the larger diameter. If there isn’t one available, get a sheet of aluminum & fabricate one. The OD should match the existing OD, but the ID will need to be smaller. You MIGHT be able to use the old large SC with a new one small as long as you can securely fasten them together, then apply silicone liberally to seal any openings.


Staff member
Nov 18, 2005
South Puget Sound, WA
What is the OD of the current chimney pipe? If DuraPlus chimney pipe is certified for installation in Canada, another option might be to use 6" DuraPlus. It is triple-walled with an OD of 10".


Minister of Fire
Nov 19, 2005
NW Wisconsin
Can you run a 6” liner down the 8” chimney pipe then reduce the stove pipe down to 6”? May save you some bucks but not sure if that’s legal?


Staff member
New flashing was running $100 2 years ago. If you get a leak, the damage will pass $100 really quickly. Why take a chance?