Need Mama Bear advice

Forgottonia

New Member
Apr 7, 2021
5
Edge of Forgottonia
Mama Bear stove.jpg

New guy here, and wood stove newb as well. Thanks for the invite!

I live in a 105 year old house in Illinois with a small detached garage. It's too small for a car (9'x18')--probably designed for a Ford Model A. So I'm converting the little garage into a workshop/man cave. I installed a hardwood floor over the concrete surface, with OSB underlayment. There's a brick chimney that extends halfway down the corner wall (see pic) with a port for a stove pipe.

I had planned to put a pot belly stove in the corner, and left an open space in the wood floor that I filled in with bricks. But then I found this Fisher Mama Bear for sale and decided to buy it instead of a pot belly stove. Problem is, the brick floor surface I had prepared for the pot belly stove doesn't fit the Mama Bear very well. I read through the "Installing and operating an old stove" thread (very helpful!) but still have a couple of questions:

1) Is 5" enough space between the brick wall and the corner of the Mama Bear? Or will the heat damage the brick wall? How much further, if any, should I move the Mama Bear out away from the brick wall?

2) How much more space will I need, if any, on the floor at the front of the stove? I have some old 1" thick pool table slate. Could I cut that in a semi-circle and lay it on the floor in front of the stove to insulate the floor? Or should I remove some of the flooring and lay a bit more brick? (The brick that the stove sits on is laying on the concrete slab.)

Many thanks for any input! Great site you have here.
 

begreen

Mooderator
Staff member
Nov 18, 2005
87,319
South Puget Sound, WA
We need more information on the wall. The concern isn't about damage to the brick, but with heat transferral to combustibles behind the brick. 5" is not enough unless everything behind the brick is non-combustible.

Is this full brick on the wall? What is behind the brick? If it is full brick with cement board then wood studs, it will permit a clearance reduction of 50%, or 18" from the back corners of the stove to the wall. The hearth needs to provide R-1.19 insulation extending to 16" in front of the stove door.
 
  • Like
Reactions: Forgottonia

bholler

Chimney sweep
Staff member
Jan 14, 2014
24,000
central pa
View attachment 277707

New guy here, and wood stove newb as well. Thanks for the invite!

I live in a 105 year old house in Illinois with a small detached garage. It's too small for a car (9'x18')--probably designed for a Ford Model A. So I'm converting the little garage into a workshop/man cave. I installed a hardwood floor over the concrete surface, with OSB underlayment. There's a brick chimney that extends halfway down the corner wall (see pic) with a port for a stove pipe.

I had planned to put a pot belly stove in the corner, and left an open space in the wood floor that I filled in with bricks. But then I found this Fisher Mama Bear for sale and decided to buy it instead of a pot belly stove. Problem is, the brick floor surface I had prepared for the pot belly stove doesn't fit the Mama Bear very well. I read through the "Installing and operating an old stove" thread (very helpful!) but still have a couple of questions:

1) Is 5" enough space between the brick wall and the corner of the Mama Bear? Or will the heat damage the brick wall? How much further, if any, should I move the Mama Bear out away from the brick wall?

2) How much more space will I need, if any, on the floor at the front of the stove? I have some old 1" thick pool table slate. Could I cut that in a semi-circle and lay it on the floor in front of the stove to insulate the floor? Or should I remove some of the flooring and lay a bit more brick? (The brick that the stove sits on is laying on the concrete slab.)

Many thanks for any input! Great site you have here.
Begreen covered the wall but the floor needs to cover 18" in all directions around the stove
 
Last edited:

Forgottonia

New Member
Apr 7, 2021
5
Edge of Forgottonia
We need more information on the wall. The concern isn't about damage to the brick, but with heat transferral to combustibles behind the brick. 5" is not enough unless everything behind the brick is non-combustible.

Is this full brick on the wall? What is behind the brick? If it is full brick with cement board then wood studs, it will permit a clearance reduction of 50%, or 18" from the back corners of the stove to the wall. The hearth needs to provide R-1.19 insulation extending to 16" in front of the stove door.
It's an exterior brick wall with two layers of bricks, almost 9" thick. There aren't any wood studs within the wall.
 

begreen

Mooderator
Staff member
Nov 18, 2005
87,319
South Puget Sound, WA
If there are no combustibles behind either wall, then 5" is fine. The hearth will need to be redone as bholler noted. He is correct about the requirement of 18" in all directions.
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,180
NE PA
If it's not difficult to remove the wood flooring, the bricks added would be level with the rest of the pad. It would also make it compliant with floor protection requirements. Normally the entire pad over a combustible material needs to be sufficient for insulating r-value and non-conductive heat flow. With this stove the protection required is quite high. Newer stoves only require ember protection, that's what you would have if you added brick over the wood flooring. You have the protection requirement covered by removing the wood under it. They get quite hot directly under the stove. The front protection that would be called a hearth extension is more for spark and ember protection than heat, but technically the extended area forward should be the minimum floor protection as required under the stove as well. This would be double cement board with brick overlay if the combustible wood is not removed.

The only issue getting too close to a non-combustible wall is since the stove radiates heat off the surface in all directions, it cools more where there is good air flow around the stove. When close to a wall, mainly in an alcove or against the back, this results in overheating the steel sheets, and warping or cracking welds due to uneven cooling. I believe Fisher recommended at least 2 inches clearance for air flow. That was one of the only warranty issues Fisher had from lack of air flow on one side creating uneven heating and cooling. They would cool from the front and stay hot on the back. Uneven expansion caused stress cracks. 5 inches is fine.

My neighbor has a Papa Bear in his basement within a foot of the cement block wall behind it. One extremely cold day he had it hot enough to heat his basement and first floor as he hasn't ran his gas furnace since installing it. The wall made a huge pop and cracked the cement block wall behind the stove. He is a mason by trade, built his entire home and of course never fixed his own. I don't imagine solid brick would do that, but any material has a certain amount of expansion with heat or moisture, so extreme heat and cold can crack most anything. If you're concerned about direct heat to the brick, a metal shield with 1 inch air space to the brick does wonders for the surface temperature. It's all about air flow taking the heat away. Open at top and bottom for air movement as the hot air rises keeping the wall cool.

There is a nationwide code restriction for the installation of any wood stove where flammable vapors are present, or in garage use. Many do it, but an insurance co. can bounce a claim if found in a garage or workshop with flammable liquids. If there are mowers or outdoor equipment with fuel in them, anything can happen to cause a leak allowing fuel vapors to get to the stove intake as an ignition source. Tractors, snow blowers, trimmers, saws. Not just motor vehicles. Never store gas or solvents in an enclosed area with the stove.
 
  • Like
Reactions: Forgottonia

EatenByLimestone

Minister of Fire
So, what have you done to ensure the chimney is safe?
 

begreen

Mooderator
Staff member
Nov 18, 2005
87,319
South Puget Sound, WA
Coaly, did these come with different leg heights? The legs on this one look a little short, but that could be the camera angle. I was wondering if that changed the hearth insulation requirements.
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,180
NE PA
Standard and minimum 6 inch. They would make them longer if requested.
 
Dec 14, 2020
160
Lisburn, PA
I haven't started working on the chimney yet. I'll get to it some time over the summer.
Some advice from one who has paid the price of not looking into all aspects of a project.
From your picture, description of the walls and the age of the building, it appears the chimney is constructed of brick.
That's probably not gonna work for Papa.
Before you work on the hearth, figure out the chimney. You may need to go to a pipe straight up thru the roof.
 
  • Like
Reactions: Forgottonia