Masonry thimble questions

Nadroj

New Member
Nov 23, 2016
17
Ohio
image.jpeg image.jpeg
I'm new to chimneys and wood stoves but I'm trying to figure out if there would be any options for my situation. I have a existing masonry chimney with a clay flue liner that is clean and in good shape. There isn't anything venting into this and I had to pull the drywall to find where the existing hole was. From reading code for my state if I re install a clay thimble into the chimney I would need to frame and build a 12 inch surround completely around the thimble to be clear of the combustibles. Am I on the right track? My other question is, is there any other options to use a different type of thimble into the masonry chimney that would reduce my clearanced and not have to brick? I am going to have a chimney sweep come verify my condition of the chimney and flue for safety before even starting the install. Thanks
 
Last edited by a moderator:
  • Like
Reactions: tnwoodburner

Nadroj

New Member
Nov 23, 2016
17
Ohio
Thanks for the reply. Yes it does help explain a little more. So it appears going with the stainless chimney pipe for thimble with the 9" airspace would be a lot easier than using the clay thimble method. When using the chimney pipe section would I just install it like a clay thimble as far as getting it flush with the clay flue and mortar in and leave the remaining length through the wall? Then I would need a a insulated chimney pipe adapter to adapt my stove pipe to the chimney thimble correct ?
 

CenterTree

Minister of Fire
Sep 15, 2008
1,047
SouthWest-Central PA
Welcome,


What stove are you going to be hooking up?
That wall hole looks very low to the floor.

Also, stick around this forum as you progress, because you will need guidance on your install as far as "Clearance to combustibles" go, and so forth.
 

Nadroj

New Member
Nov 23, 2016
17
Ohio
I'm not sure as to a stove yet. That was my next situation I was going to tackle if the chimney is safe and I find out exactly what I need as far as a thimble goes. From the floor to the center of the hole for the thimble I only have about 30" which is really low. So far looking at stoves locally my choices are super slim. Only options seem to be a stove that exits from the rear or I've seen the small us stove logwood cast iron stove. The smallest one the model 1261 may set low enough to be able to come up just a bit and 90 into the thimble but I'm not sure yet. When I talked to the chimney sweep he said if it is to low that it is possible to close that one and open another but that would just be something else I'd have to do.
 

begreen

Mooderator
Staff member
Nov 18, 2005
84,891
South Puget Sound, WA
There are several rear-exit stoves on the market, most are cast iron, but there also is a Buck and a High Valley model in steel. Before proceeding with stove selection you'll need to verify that the chimney is safe to use and the liner is sized correctly for the stove. The majority of stoves today take a 6" flue. That would require a chimney flue with a cross section area of about 28 sq. in..
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
22,486
central pa
Also if you are already redoing the thimble why not just move it up so you have more choice in stoves
 

begreen

Mooderator
Staff member
Nov 18, 2005
84,891
South Puget Sound, WA
If you do, be sure to seal up the old hole well with brick and mortar.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
22,486
central pa
If you do, be sure to seal up the old hole well with brick and mortar.
yeah or make it a cleanout either way it needs sealed up
 

Nadroj

New Member
Nov 23, 2016
17
Ohio
I may end up moving the hole up higher I'm just not sure if I want add more work into filling that one in and cutting a new one. The chimney will be inspected prior to installing anything and I'll consult them to what they would think be best. My clay flue liner I have now is 6" I believe. Most stoves I've been seeing take a 6" pipe. When I checked the flue it appeared to be a 6" flue so that would work for the 28" cross section area needed correct? I already have one clean out on the outside of the chimney. I do have to replace the door on that also to meet code.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
22,486
central pa
I
may end up moving the hole up higher I'm just not sure if I want add more work into filling that one in and cutting a new one. The chimney will be inspected prior to installing anything and I'll consult them to what they would think be best. My clay flue liner I have now is 6" I believe. Most stoves I've been seeing take a 6" pipe. When I checked the flue it appeared to be a 6" flue so that would work for the 28" cross section area needed correct? I already have one clean out on the outside of the chimney. I do have to replace the door on that also to meet code.
doubt it is 6" clay they did make them but they are very uncommon it is most likely an 8x8 clay liner which is more like 7 to 7.25 inside measurement. If it is good shape it is worth trying a stove in it to see how it works but an insulated liner would work much better.
 

Nadroj

New Member
Nov 23, 2016
17
Ohio
image.jpeg
Measuring my clay flue the inside seemed to measure out roughly 6"x7 1/4". From the looks of it, I'm not sure if anyone has ever used it. It's super clean. Does anyone know the procedure on installing the class a chimney pipe into the flue if I use that as a thimble instead of the clay thimble? Does it just slide in flush to the flue then mortar it in or is it attached with a bracket and secured into the chimney block?
 
Last edited by a moderator:

bholler

Chimney sweep
Staff member
Jan 14, 2014
22,486
central pa
Measuring my clay flue the inside seemed to measure out roughly 6"x7 1/4". From the looks of it, I'm not sure if anyone has ever used it. It's super clean. Does anyone know the procedure on installing the class a chimney pipe into the flue if I use that as a thimble instead of the clay thimble? Does it just slide in flush to the flue then mortar it in or is it attached with a bracket and secured into the chimney block?
Just use an insulated wall passthru they are made specifically for your application. And when you decide to line the chimney it will work with the liner as well
 

begreen

Mooderator
Staff member
Nov 18, 2005
84,891
South Puget Sound, WA
They are mentioned toward the end of the article link previously posted.
 

Nadroj

New Member
Nov 23, 2016
17
Ohio
Yea sorry I see that now. I don't know how I skipped over them. Looks like they are pretty pricey. These prices keep adding up it almost makes me just want to look into doing through the ceiling kit with class a stainless chimney.
 

Ashful

Minister of Fire
Mar 7, 2012
15,715
Philadelphia
Going straight out the back of a stove to a thimble is not a recipe for good draft. If your chimney is tall, it can overcome this deficiency, but if it is less than 20 feet you should really consider moving that thimble up a bit.
 

Nadroj

New Member
Nov 23, 2016
17
Ohio
Ok thanks for the heads up. Moving it up would make my options so much easier and pretty well let me pick whatever stove fits my needs best instead of searching for a handful that would work for the lower thimble. What's the usual procedure for filling in a unused thimble?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
22,486
central pa
Ok thanks for the heads up. Moving it up would make my options so much easier and pretty well let me pick whatever stove fits my needs best instead of searching for a handful that would work for the lower thimble. What's the usual procedure for filling in a unused thimble?
it can work just fine but straight up is always better
 
Jan 1, 2015
2
Massachusetts
If you go forward with this project, when you finally connect your stove to the thimble be sure the flue pipe from your stove fits around the outside of the thimble. If you use an adapter, make sure the adapter fits inside the connection to your stove or inside the pipe from your stove, and then fits around the outside of your thimble. Don't ask me how I know this!
 

Ashful

Minister of Fire
Mar 7, 2012
15,715
Philadelphia
Why not install a clean out door on the old thimble, and leave it? It would make cleaning out the sweepings a snap!
 

Nadroj

New Member
Nov 23, 2016
17
Ohio
If I abandon that hole for a higher thimble I don't think I'd want a clean out door on my interior wall.
 

begreen

Mooderator
Staff member
Nov 18, 2005
84,891
South Puget Sound, WA
Why not install a clean out door on the old thimble, and leave it? It would make cleaning out the sweepings a snap!
I already have one clean out on the outside of the chimney. I do have to replace the door on that also to meet code.
 
  • Like
Reactions: Ashful

bholler

Chimney sweep
Staff member
Jan 14, 2014
22,486
central pa
If I abandon that hole for a higher thimble I don't think I'd want a clean out door on my interior wall.
then just cover over it especially if you already have a cleanout out side. I don't know that you have to replace the door to meet code but you want to make sure it seals well for performance reasons.
 

Nadroj

New Member
Nov 23, 2016
17
Ohio
image.jpeg
The reason I have to change the clean out door is whoever built the chimney put in a fireplace ash door instead of a clean out door. I'll have to pull it and cut it out a little more to put in an actual clean out door. I do appreciate all the responses I've got from everyone. It's helped out a lot. Looks like the sat-t-thimble or the Olympia wall thimble are two options I'm going to look at for this. I'm gonna look into them both some more and see when I can have the chimney sweep come out. When I called the ther day it would be into December before he could make it out. So once he comes to check the chimney for safety I'll ask him about my plan. I'll be having them come back out after I do the install to do an installation inspection for insurance and make sure everything is good.
 
Last edited by a moderator: