Installing wood stove in unfinished basement: Chimney clearance questions

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.

MTBSully

New Member
Oct 8, 2021
5
03840
First post here. Looking to add a wood burning stove to my unfinished basement to help heat my house this winter. I have some questions about chimney clearance indoors and want to make sure this is done correctly.

Id like the stove to be in the corner as shown below, and am hoping i can run the chimney/thimble through the wall between the joists so I wont have to cut a hole in my foundation. This is where I need some clarification. Can the chimney/thimble run through the wall between the joists? Ive read if the pipe is double or triple wall (class A?) chimney pipe, it only needs to be 2" from combustible materials. Other places I have read it is 8" or so. My newer boiler setup runs the exhaust exactly this way in the next room over (out of the picture) but it was installed before I bought the house, so I don't know if it is to code or not.

Excuse the crude paint drawings, but just to give you an idea of what im talking about.

20211007_183936.jpg 20211007_183929.jpg



I beleive the studs are 16" on center, so if the 2" rule is correct I should have plenty of room on sides and top to have the chimney exit in this location, just wanted to see what the experts had to say.

And from the outside. You can see my boiler chimney on the right.

Screenshot_20211008-085257_Messages.jpg

I am located in NH and the local building inspector said we use ICC 2015 buillding code if that helps at all. I appreciate any and all input.

Chris
 
Last edited:

Beary

New Member
Sep 30, 2021
10
North idaho
Your going to want a significantly taller chimney for the wood stove than what's on that boiler, else you're going to have some hellish draft issues...

The real experts will chime in soon tho and know lots more about your clearance questions.
 
  • Like
Reactions: MTBSully

MTBSully

New Member
Oct 8, 2021
5
03840
Your going to want a significantly taller chimney for the wood stove than what's on that boiler, else you're going to have some hellish draft issues...

The real experts will chime in soon tho and know lots more about your clearance questions.

Yes i figured. More concerned about indoor clearance requirements. Outside ive got plenty of room
 

kborndale

Feeling the Heat
Oct 9, 2008
299
LI
You do realize that a majority of the heat you produce will be going to heat the concrete walls/floor and the dirt on the other side of them?
 
  • Like
Reactions: PaulOinMA

gthomas785

Feeling the Heat
Feb 8, 2020
493
Central MA
Everything you're proposing sounds pretty doable. Make sure you read up on the distinction between "Chimney pipe" and "stove pipe" which I believe is where the confusion about clearances came from. Stove pipe can only be used in the same room as the stove and has larger clearance requirements, and must transition to a chimney before leaving the room.

The clearances for any given piece are determined by the manufacturer so check the manual of whatever stove and venting products you plan to use and just make sure you meet those everywhere. If the wall pass through is tight, there are insulated thimbles available that are rated for zero clearance.

Just a question though, why do you want to put the stove in the basement rather than in the house where you can enjoy it? Unless your basement is really well insulated and you have an open stairway up into the house, I think you'll find the heating performance to be lackluster. Unless you are specifically trying to heat the basement so you can work down there or whatever.
 
  • Like
Reactions: Beary

kennyp2339

Minister of Fire
Feb 16, 2014
5,924
07462
No good, class A pipe needs 1" clearance around all wooden combustibles, the through the wall kit that provides the space is larger then the 2x10 your trying to go through, its best to chisel the hole through the block wall, on the outside of the house dig a well and mount the anchor plate, leaving enough room to access the cleanout cap on the T, as far as chimney height, you will need to follow the 2-3-10 rule, forget the 2 which represents 2ft higher then the peak of the roof (more center mounted chimney) your going to want to be 3ft higher then the nearest thing in a 10ft radius from the chimney cap.
 

stoveliker

Minister of Fire
Nov 17, 2019
1,491
Eastern Long Island NY
Do you have another window as the one to the left of your indicated location? That one can't be used (other windows above), but using "a" window likely will help with the clearances, and prevents chiseling.

Of course a proper way to secure the passage through the opening needs to be put in place.
 

MTBSully

New Member
Oct 8, 2021
5
03840
Everything you're proposing sounds pretty doable. Make sure you read up on the distinction between "Chimney pipe" and "stove pipe" which I believe is where the confusion about clearances came from. Stove pipe can only be used in the same room as the stove and has larger clearance requirements, and must transition to a chimney before leaving the room.

The clearances for any given piece are determined by the manufacturer so check the manual of whatever stove and venting products you plan to use and just make sure you meet those everywhere. If the wall pass through is tight, there are insulated thimbles available that are rated for zero clearance.

Just a question though, why do you want to put the stove in the basement rather than in the house where you can enjoy it? Unless your basement is really well insulated and you have an open stairway up into the house, I think you'll find the heating performance to be lackluster. Unless you are specifically trying to heat the basement so you can work down there or whatever.

Ive determined there is no good place for another stove on the first floor. There is already a propane stove in the living room and I cant see any logical location for it anywhere else. I realize I will lose some heat into the concrete walls and floor, but i will be leaving the basement door open and also intend to cut install some vents in the first floor to allow heat to rise to that level.

No good, class A pipe needs 1" clearance around all wooden combustibles, the through the wall kit that provides the space is larger then the 2x10 your trying to go through, its best to chisel the hole through the block wall, on the outside of the house dig a well and mount the anchor plate, leaving enough room to access the cleanout cap on the T, as far as chimney height, you will need to follow the 2-3-10 rule, forget the 2 which represents 2ft higher then the peak of the roof (more center mounted chimney) your going to want to be 3ft higher then the nearest thing in a 10ft radius from the chimney cap.

Was hoping to avoid chiseling into the foundation. Hmm.

Do you have another window as the one to the left of your indicated location? That one can't be used (other windows above), but using "a" window likely will help with the clearances, and prevents chiseling.

Of course a proper way to secure the passage through the opening needs to be put in place.

I have another window but its also below another window. My other thought was come out that bottom window and use a couple 30 degree elbows to get around the window its below. Thoughts?
 

Bad LP

Minister of Fire
Nov 28, 2014
1,719
Northern Maine
You will lose more than “just some heat” if those basement walls are not insulated on the inside. You will lose most of your heat.

Been there, done that on a stove that ate 30” logs. Very little heat went up the stairway. Installed 2” Dow foam board to the walls and it was over 80 in the basement with the warmth pouring out the cellar door.
 

stoveliker

Minister of Fire
Nov 17, 2019
1,491
Eastern Long Island NY
Yes, if you go the stove-in-basement route, the next project should be insulating the basement. Carefully check the best practices to do so to avoid moisture/rot/mold. This should include the bays where you now have stuffed batts in the pic (that is not the right way to insulate these bays and risks rot in the sil beam).
Cutting, splitting, stacking 30% less wood...

Regarding avoiding the window, the more angles (you already would have two 90s) you include, the more poor your draft will be. But 30 degree offsets are not that bad, and you have some length to do to clear the roof. I think you will be ok with that. It may not look nice though. Do aim to limit the horizontal run of the (double wall!) stove pipe inside as much as possible.
 

begreen

Mooderator
Staff member
Nov 18, 2005
89,479
South Puget Sound, WA
In the basement, the pipe would typically transition to a connector pipe. There is not enough clearance between the floor joists for any connector there. And one has to allow for the thimble dimension which will be 12" OD. Is there enough room for that? If yes, then I am wondering if you could come off the horiz. section with a down-facing 45º class A elbow, but that would still take some measuring for the connector clearance coming off of it and acceptance by the local inspector.

Outside, the other existing chimney looks too short. Is it on a wood boiler? It has to at least honor the 10-3-2 rule and provide enough draft for the stove. Typically this is 15-16' vertical.
 

MTBSully

New Member
Oct 8, 2021
5
03840
I think im giving up on the through-joist idea for now and going to go the thru-concrete. Emailed a few local companies to drill a hole for the thimble in the concrete right to the left of the window. A little more work, but I know it will have the proper clearance to combustible materials.
 

begreen

Mooderator
Staff member
Nov 18, 2005
89,479
South Puget Sound, WA
Several years ago we had a few people post threads with a similar situation. One hired a professional core cutter to make a hole large enough to clear the class A pipe. Another used a heavy duty hammer drill, and long masonry bit to drill a ring of holes and then chiseled them smoother. Be sure to make a proper and safe well for the tee. Also, consider screening the well to prevent leaves from accumulating there. That can be a serious fire hazard.
 

MTBSully

New Member
Oct 8, 2021
5
03840
Several years ago we had a few people post threads with a similar situation. One hired a professional core cutter to make a hole large enough to clear the class A pipe. Another used a heavy duty hammer drill, and long masonry bit to drill a ring of holes and then chiseled them smoother. Be sure to make a proper and safe well for the tee. Also, consider screening the well to prevent leaves from accumulating there. That can be a serious fire hazard.

Ive already got a quote from a pro to core drill it. Not wanting to monkey around with my foundation and drill 20 holes and have a crappy looking large hole all said and done. Do you have a link to the thread?