New Member Setting Up Masonry Chimney for BK

[MaudSTL]

Hello, everybody! I have been reading this forum for awhile to learn more about heating with wood stoves. I am currently setting up a chimney for a Blaze King, and would like to check to make sure I am not making any mistakes so I do it right the first time. Sorry this is so long.

Background
My house will need supplemental and back-up heating for power failures, as we get ice storms here that have been known to cause outages lasting days or a week. This means a wood stove at my house might only be operated for a few weeks or a month in late December and into January, our coldest month.

I am looking at a Blaze King Boxer 24 or Chinook 30.2. I am attracted to Blaze King because of the long, low burn times. It will be my first and only (I hope) wood stove. I understand from reading this site and the stove manuals that proper draft and dry wood are critical for EPA stoves like these. Because I plan to age in place, I care a lot about energy efficiency. Because my health is already declining, I don’t want to have to load a stove any more often than necessary. On page 16 of the stove manual https://www.blazeking.com/wp-content/uploads/2018/11/OM-BX24-E.pdf is a drawing of an installation in a masonry chimney. My chimney flue has no jog in it...it just goes straight up. And it doesn’t have a big open space below the tee either.

Since my recent retirement, I have been working on renovating a 1903 two and a half story house in St. Louis, MO. Urban houses like mine are tall and skinny, and they are full masonry, with the front of the house three stories tall and the back of the house two stories tall. The floor plan is shotgun style. The first floor is about 720 sf, with three rooms and a long hallway on the west with two staircases, one to the second floor and the other to the third floor. Houses like mine were designed to act like giant chimneys, back when fuel and labor were cheap.

Both my roofs are flat, with rigid insulation and TPO roofing. I will be adding as much insulation as I can, both under the roofs and in walls that can be furred out. I will be adding wooden storm windows to windows that have already been weatherstripped with interlocking tee-shaped and vee-shaped weatherstripping. The first through third floors will have exhaust fans in the bathrooms and over the cooktop, and the clothes dryer on the second floor will be ventilated to the exterior. Although the first through third floors will be pretty air tight other than exhaust fans, the basement will be unconditioned and leaky. It will contain no combustion appliances, as the heating/cooling and DHW will be electric. There are floor grates from the basement to the first floor, left over from the days when there was a big coal furnace in the basement that is now gone. So I am looking to the basement to provide fresh air to the wood stove.

Chimney/Flue
The wood stove will be in the back room on the first floor, which is only 12.5’ x 12.5’ x 10’ high and is the northernmost room on the first floor, right next to the staircase to the third floor. The chimney is on the exterior wall, which is typical of houses like mine. The chimney has three flues, and my friend Karl and I opened up the northernmost flue for the stove chimney. This means the stove chimney will be 10’ away from the back of the third floor. The other two flues will not be in use.

To make sure the chimney is high enough, I have asked my mason friend Lenny to rebuild the chimney to extend just the stove flue, restoring the original height of 6’ above the second floor roof. Years ago, Karl and I took down the chimney to parapet height because it was in danger of falling down. So Lenny will rebuild an unlined 18” x 18” (exterior) chimney above the parapet. The interior of the chimney will be about 10” x 10”.

Karl and I plan to use a 6” smooth wall flexible stainless steel liner with a tee at the bottom and a stainless steel anchor plate on top. Because the chimney will be 2’ shorter than the third floor roof height, we will attach a 6” x 4’ Class A pipe to the anchor plate, topped with a rain cap with a spark arrester. This will being the chimney height up to 2’ above the highest part of the house. From the top of the Class A pipe to the thimble on the first floor will be about 26’.

Because the flue is very uneven on the interior, we are concerned that liner insulation might tear. So, even though the flue measures 10” x 10”, we plan to pull and center the 6” liner, and then fill the flue around the liner with vermiculite slurry. I plan to pack the area around the tee at the bottom of the liner with Roxul insulation.

Does all this seem OK so far?

Air Intake
The Boxer 24 has no fresh air intake kit. Because my basement is leaky and unconditioned, should I cut a grate into the floor under the stove to supply fresh air? If Yes, where should I locate it? The manual doesn’t describe where the stove pulls in air...

Clean-out
To clean the chimney, I wonder if I can install a cast iron clean-out door somewhere low in the flue...I’m not sure where. We already opened the chimney breast to a level about 3+’ off the floor, which would be at the same height as the top of the stove, and cleaned out the flue. I was thinking we could install a clean-out door there, so I can reach in and up, put a little box under the tee, pull the bottom of the tee off, and let the creosote fall into the box. I hope someone can advise if we need to place the clean-out somewhere else or structure it in a different way.

Wall Surface Behind Stove
I have salvaged a lot of slate shingles, and was planning to install concrete board over the chimney breast (which is brick with 1” of plaster on it) and then shingle the concrete board with the slate, using copper nails. Does this sound OK or do I need to build a structure that provides an air gap behind it?

Thank you!

 

[begreen]

You are on the right track. One of the byproducts of burning low and slow will be a cooler flue. In an all masonry product, especially an unlined one, creosote accumulation needs to be watched. An insulated, stainless steel liner in the chimney flue will keep the flue gases hotter, thus reducing accumulation. It will also improve draft. I don't think the vermiculite slurry is necessary. You can get a stainless steel mesh sock available that sleeves the insulation to protect it when pulling. Pros use a heavy-duty liner instead of a 2 ply smooth liner. The smooth wall liners often have issues with interior puckers and fish mouths.

There should be no need to worry about an air gap, it sounds like the entire wall behind the stove is non-combustible. However, I am not sure about hanging the slate shingles vertically. You may want to do a bit more research on this.

 

[MaudSTL]

You are on the right track. One of the byproducts of burning low and slow will be a cooler flue. In an all masonry product, especially an unlined one, creosote accumulation needs to be watched. An insulated, stainless steel liner in the chimney flue will keep the flue gases hotter, thus reducing accumulation. It will also improve draft. I don't think the vermiculite slurry is necessary. You can get a stainless steel mesh sock available that sleeves the insulation to protect it when pulling. Pros use a heavy-duty liner instead of a 2 ply smooth liner. The smooth wall liners often have issues with interior puckers and fish mouths.

There should be no need to worry about an air gap, it sounds like the entire wall behind the stove is non-combustible. However, I am not sure about hanging the slate shingles vertically. You may want to do a bit more research on this.

Thank you. One of the other reasons for the vermiculite insulation is to help hold the chimney flue together. In a 1903 building, the mortar is long dead and gravity is really what keeps the building standing. I can tuckpoint what I can see, but opening a chimney to rebuild the flues is a huge, unaffordable job. It doesn’t show in the photos, but some of the bricks in the flue are loose and there’s no way to get to them to correct them. I am hoping the vermiculite insulation will exert some lateral pressure to push loose bricks back in place and to fill gaps where the mortar is lost.

I’m concerned about the puckers you mention in the smooth wall liner...didn’t realize that was a feature. I figured two ply had to be better than a single ply. I went with flexible for cost and because I have an unaffordable quote from a good chimney man who didn’t want to build to 10’ above the roof. I don’t feel good about cutting that corner, since the flue is right at 10’ from the third floor. That’s why Karl and I decided to line it ourselves.


Please help me understand your concern about the slate shingle pattern. I’ve attached a photo of how they are installed on the mansard so you can get an idea of what they look like. I was envisioning the concrete board being whatever width the stove manual specifies, and then clad with the slate shingles exactly as they appear on the mansard. I salvaged some copper that I can use to edge it on the sides, so I think it will look nice. But I don’t want to do anything that will interfere with the effectiveness of the stove.

 

[begreen]

My concern with the slate is that the copper nails will only have 1/2" material to sink into for an anchor. Cement board will not afford much holding power for the nails. It's not like nailing into wood.

 

[MaudSTL]

My concern with the slate is that the copper nails will only have 1/2" material to sink into for an anchor. Cement board will not afford much holding power for the nails. It's not like nailing into wood.

Ah. I see. I was going with the copper nails because I already have some left over from the mansard. I will experiment with silicone caulking and/or this hook system. https://www.stortz.com/product-category/roofing-tools/slate-roofing/slate-hooks/ Thanks.

I have another question. The chimney supply guy advised me to pour the vermiculite insulation only around the liner and not around the tee attached at the bottom. I didn’t ask him why, but of course now I am wondering about it. The only idea I can think of is that the tee would remain serviceable in the future if it weren't encapsulated in the insulation. That’s why I thought I should insulate the area around the tee with Roxul.

 

[bholler]

Ah. I see. I was going with the copper nails because I already have some left over from the mansard. I will experiment with silicone caulking and/or this hook system. https://www.stortz.com/product-category/roofing-tools/slate-roofing/slate-hooks/ Thanks.

I have another question. The chimney supply guy advised me to pour the vermiculite insulation only around the liner and not around the tee attached at the bottom. I didn’t ask him why, but of course now I am wondering about it. The only idea I can think of is that the tee would remain serviceable in the future if it weren't encapsulated in the insulation. That’s why I thought I should insulate the area around the tee with Roxul.

You can absolutely use pour in insulation around the tee. And in a case like yours I would probably use pour in. It does do a good job of stabalizing an old chimney structurr

 

[MaudSTL]

You can absolutely use pour in insulation around the tee. And in a case like yours I would probably use pour in. It does do a good job of stabalizing an old chimney structurr

Thank you.

Back to the fresh air supply. I wrote to BK to confirm where the air intake is located on the Boxer 24. It is in the center of the front, which of course makes sense because it is really a stove insert in a box.

In the room where the stove will be, there are already two floor registers cut into the floor in the vicinity of the stove. One is about 8’ away from the front of the stove, and the other is about 8’ away on the left side of the stove. Both these registers open directly to the basement, and have no ducts because I already tore out all the sheet metal from the old forced air system. (I will be heating and cooling the house with Mitsubishi mini splits instead of forced air.)

Will the two registers, each about 8’ away, be an adequate source of fresh air? Or should I cut another hole in the floor directly in front of the stove?

 

[bholler]

Thank you.

Back to the fresh air supply. I wrote to BK to confirm where the air intake is located on the Boxer 24. It is in the center of the front, which of course makes sense because it is really a stove insert in a box.

In the room where the stove will be, there are already two floor registers cut into the floor in the vicinity of the stove. One is about 8’ away from the front of the stove, and the other is about 8’ away on the left side of the stove. Both these registers open directly to the basement, and have no ducts because I already tore out all the sheet metal from the old forced air system. (I will be heating and cooling the house with Mitsubishi mini splits instead of forced air.)

Will the two registers, each about 8’ away, be an adequate source of fresh air? Or should I cut another hole in the floor directly in front of the stove?

They probably will but i can't say. Honestly most houses are leaky enough that outside air really is not nessecary.

 

[MaudSTL]

They probably will but i can't say. Honestly most houses are leaky enough that outside air really is not nessecary.

Thanks. I think I will try it and see how it works, because I don’t want to cut more holes in the floor if I can avoid it, plus the staircase to the third floor is almost beside the stove location, So that will create a lot of draw.

On to my final question. If I encapsulate the tee under the liner in pour-in insulation, do I eliminate the possibility of extending the tee to a clean-out lower in the flue? I have seen photos of a single wall pipe (capped at the bottom) extended down into the flue, with an access door to it. I have wondered whether this is desirable for a wood stove, because you don’t want the chimney to try to draw from anywhere but the stove. How do most people with my kind of set-up handle clean-out?

 

[bholler]

Thanks. I think I will try it and see how it works, because I don’t want to cut more holes in the floor if I can avoid it, plus the staircase to the third floor is almost beside the stove location, So that will create a lot of draw.

On to my final question. If I encapsulate the tee under the liner in pour-in insulation, do I eliminate the possibility of extending the tee to a clean-out lower in the flue? I have seen photos of a single wall pipe (capped at the bottom) extended down into the flue, with an access door to it. I have wondered whether this is desirable for a wood stove, because you don’t want the chimney to try to draw from anywhere but the stove. How do most people with my kind of set-up handle clean-out?

I always extend down to a clean out when possible. It just required another tee and a bit of liner.

 

[MaudSTL]

I always extend down to a clean out when possible. It just required another tee and a bit of liner.

So the bottom of the tee at the thimble would have a single wall pipe extension to a second tee lower in the flue that would have a clean-out door.

Does code requires the clean-out to be at a certain distance away or at a certain height from the floor?

 

[bholler]

So the bottom of the tee at the thimble would have a single wall pipe extension to a second tee lower in the flue that would have a clean-out door.

Does code requires the clean-out to be at a certain distance away or at a certain height from the floor?

Just a certain height from the floor. You can use single wall but it needs to be stainless. I usually just use a section of liner

 

[MaudSTL]

Just a certain height from the floor. You can use single wall but it needs to be stainless. I usually just use a section of liner

Thank you!