Clearances Reduction thoughts for Mama Bear

[harbinger50]

Hi everyone! New to the forum and trying to read as much as I can, but still wanted to post up with a couple ideas and or questions.

I got a mama bear from a friend who's grandparents had moved it out to a shop for storage for the last 30+ years. Outside of some surface rust (took care of that with a drill/wirebrush) and one broken firebrick (replaced), this thing seems to be in great shape.

Following links from some of the threads here, I found the listed clearances and holy crap those are some big clearances! haha. Moving the stove to those distances put's in the way in my living room and too close to furniture.

Long story short, I'm looking for ways to reduce the clearances to the walls. It's going in a corner and facing out diagonally. So that corner section of wall needs some protection and the cheaper (but still safe) the better.

I've seen suggestions for sheet metal with spaces an inch out which is one possibility, but then I stumbled upon something I haven't seen mentioned here and wondered if it could work: Welding blankets. These things are rated to 1800 degrees and I was wondering if they could be hung up like curtains with the same distances as the sheet metal, with the gap at the bottom, behind, and at the top.

Anyone tried this or think it could work?

Oh, and I have a tile floor. Do I need to do anything for the floor under the stove?

Thanks.

 

[begreen]

Welding blankets may be good insulation but not tested in this application. I don't think that would be cheaper than a cement board shield. The installation will require NFPA 211 wall shielding to reduce the corner clearance down to 12".
https://www.hearth.com/talk/threads/wood-stove-wall-clearances-primer.147785/#post-1987380

Is this ceramic tile on the floor? What is under the tile?

 

[coaly]

You will be limited to 18 inches from single wall pipe, or need double wall close clearance pipe which is good down to 6".

Single rock board under tile is not enough.
I added a heat shield under my Mama on a tile floor over cement board. Went from uncomfortably warm to cold in the center under stove.

Raised on bricks as well for more clearance. I put stick-on felt on the bottom of bricks to protect flooring.

 

[Todd67]

Welcome to the forum, and congrats on your "new" Fisher stove.

There are some good ideas posted above. I installed my Mama Bear in a corner of my living room, between two windows. Having window blinds that close to a woodstove forced me to keep those at 36" from the stove. I also wanted my hearth to be big enough to hold two tall racks of firewood. Living in northern NY and getting anywhere between 10ft to over 20ft of snow every winter, those log racks on the hearth allow my firewood to dry before I burn the wood. I also went with a thicker/taller hearth floor because of the old hardwood flooring that is in my living room. I used two layers of cement board on the metal 2x4 studs (wall & floor), with the seems staggered.

Here is a link to my Mama Bear installation, just for the purpose of generating some ideas for you. This Mama Bear has been our only heat source for 7 winters now, in our 2 story house, and there's nothing I would change about the installation. At first I thought the hearth was too big, and that it stuck too far out into the living room, but in fact, it's big enough to protect our floors from Sparks, and from snow/ice that melts off our firewood.

https://www.hearth.com/talk/threads/mama-bear-restoration-and-installation-project.91558/

 

[harbinger50]

Welding blankets may be good insulation but not tested in this application. I don't think that would be cheaper than a cement board shield. The installation will require NFPA 211 wall shielding to reduce the corner clearance down to 12".
https://www.hearth.com/talk/threads/wood-stove-wall-clearances-primer.147785/#post-1987380

Is this ceramic tile on the floor? What is under the tile?

It is ceramic tile with cement board underneath. Thanks for the link!

 

[harbinger50]

You will be limited to 18 inches from single wall pipe, or need double wall close clearance pipe which is good down to 6".

Single rock board under tile is not enough.
I added a heat shield under my Mama on a tile floor over cement board. Went from uncomfortably warm to cold in the center under stove.

View attachment 238747 Raised on bricks as well for more clearance. I put stick-on felt on the bottom of bricks to protect flooring.

So are you saying the clearances for the stove pipe are all that matter?

I bought Selkirk double wall pipe.

As for underneath the stove needing more shielding ... what is your heat shield underneath? I DO have some more bricks lying around and could raise it the same way you did, so that's a step I can take.

 

[harbinger50]

Welcome to the forum, and congrats on your "new" Fisher stove.

There are some good ideas posted above. I installed my Mama Bear in a corner of my living room, between two windows. Having window blinds that close to a woodstove forced me to keep those at 36" from the stove. I also wanted my hearth to be big enough to hold two tall racks of firewood. Living in northern NY and getting anywhere between 10ft to over 20ft of snow every winter, those log racks on the hearth allow my firewood to dry before I burn the wood. I also went with a thicker/taller hearth floor because of the old hardwood flooring that is in my living room. I used two layers of cement board on the metal 2x4 studs (wall & floor), with the seems staggered.

Here is a link to my Mama Bear installation, just for the purpose of generating some ideas for you. This Mama Bear has been our only heat source for 7 winters now, in our 2 story house, and there's nothing I would change about the installation. At first I thought the hearth was too big, and that it stuck too far out into the living room, but in fact, it's big enough to protect our floors from Sparks, and from snow/ice that melts off our firewood.

https://www.hearth.com/talk/threads/mama-bear-restoration-and-installation-project.91558/

Reading over your thread now... thanks for the link!

 

[Todd67]

Reading over your thread now... thanks for the link!

It was my first wood stove installation, and my first wood stove ever. So I went overboard with my hearth clearances. In hind sight, I could've used just one layer of cement board instead of two layers. But I had no idea how hot the bottom of the stove would get.

 

[harbinger50]

It was my first wood stove installation, and my first wood stove ever. So I went overboard with my hearth clearances. In hind sight, I could've used just one layer of cement board instead of two layers. But I had no idea how hot the bottom of the stove would get.

It looks great!

I do have some extra boxes of the tile I used on my floor, so maybe I could do something similar but that seems really involved. Don't have a lot of spare money now, especially after looking at my taxes but already have the stove, stove pipe, and chimney pieces here, so the easiest and cheapest, while being safe, option is what I'm trying to determine. Maybe if I was convinced this was my last house ever, I'd build out something like yours, but I'm looking (many years down the road) to find or build a house closer to the mountains on a good chunk of land (10 acres +) and would probably take the wood stove with me.

 

[Todd67]

It looks great!

I do have some extra boxes of the tile I used on my floor, so maybe I could do something similar but that seems really involved. Don't have a lot of spare money now, especially after looking at my taxes but already have the stove, stove pipe, and chimney pieces here, so the easiest and cheapest, while being safe, option is what I'm trying to determine. Maybe if I was convinced this was my last house ever, I'd build out something like yours, but I'm looking (many years down the road) to find or build a house closer to the mountains on a good chunk of land (10 acres +) and would probably take the wood stove with me.

Thanks!

I understand keeping the cost down. I don't plan on moving, but if I did, the hearth and chimney would stay with this house. I would take my Mama Bear with me... she's part of the family

The cement board isn't too pricey. I wonder if you could lay a piece of cement board down, then some tile over it, then set the stove legs on a brick. Our cats lay right up close to the woodstove once we turn the draft caps down. They lay a foot away from it right after we load it with wood, so it can't be that hot on the floor, can it?

 

[Todd67]

Thinking about keeping the cost down, I guess the cheapest (low cost) option is to put the stove far enough away from the back wall so that you don't need any heat shields back there. Yes, you would lose some floor space that way, but it would save money on materials.

 

[coaly]

So are you saying the clearances for the stove pipe are all that matter?

I bought Selkirk double wall pipe.

As for underneath the stove needing more shielding ... what is your heat shield underneath? I DO have some more bricks lying around and could raise it the same way you did, so that's a step I can take.

No, when reduced clearance is used with an approved shield (down to 12 inch minimum) the pipe becomes the clearance factor (18 inches) requiring shielding of the pipe, or easier to use close clearance pipe.

In the photo it is the unpainted silver "shelf" that was actually from metal shelving I cut down to the size of the stove bottom to fit between the legs. I put small clamps on the legs to support it without modifying the stove or drilling holes in the legs.

Floor protection would need double rock board and tile, or solid brick over the single rock board. (with sheet metal as specified in NFPA 211 12.5.1.2.1. Which is for legs with min. 6 inch clearance under appliance. This is the reason Fisher used min. 6 inch legs and 12.5.1.2.2 is for stoves with legs from 2 to 6 inches requiring more protection {hollow bricks} such as the All-Nighter brand) The actual formula uses 3 factors, R-Value, (or thermal resistance) k-factor, (or thermal conductivity) and C-Factor. (Thermal conductance) Some materials that are good in one factor are not good in others. So it becomes complicated and the easiest way was to simply require 3/8 asbestos millboard with a covering of brick or equivelant. Since that base material doesn't exist anymore, and to calculate an equivelant, you're back to calculations. Since like you, I already had single layer rock board and finished tile, I added the metal shield under the stove to reduce radiation.

 

[coaly]

Thanks!

I understand keeping the cost down. I don't plan on moving, but if I did, the hearth and chimney would stay with this house. I would take my Mama Bear with me... she's part of the family

The cement board isn't too pricey. I wonder if you could lay a piece of cement board down, then some tile over it, then set the stove legs on a brick. Our cats lay right up close to the woodstove once we turn the draft caps down. They lay a foot away from it right after we load it with wood, so it can't be that hot on the floor, can it?

Single cement board and tile is less than "the equivalent of 3/8 millboard and solid brick". You can do a calculation of any proposed system converting specs to R-Value. Some materials only give C and k factors, so they have to be converted to R Value and added up for the total value of the system.

 

[Todd67]

Single cement board and tile is less than "the equivalent of 3/8 millboard and solid brick". You can do a calculation of any proposed system converting specs to R-Value. Some materials only give C and k factors, so they have to be converted to R Value and added up for the total value of the system.

I haven't looked at the codes and regs since 2012, so I don't remember all the important numbers. I know that I wasn't willing to spare any expenses with my hearth material or clearances when I installed my stove. The extra money I spent on hearth materials was much less than the cost of replacing my house if it burned down.

 

[Todd67]

@coaly , I also wasn't sure if putting cement board on top of his existing tile floor, with more tile on top, would meet the requirements. He already has cement board under his tile floor, so it would be two layers of tile and two layers of cement board.

 

[coaly]

That would be fine too. A stove board that is UL approved is the simplest solution under the stove.
https://www.amazon.com/dp/B0062MAQ5E/?tag=hearthamazon-20

They work good for wall protection too. Not too heavy. My Kitchen Queen required a bit more protection than the single layer under my tile so I sat the cookstove on the largest one available. I find as a stove expands and contracts with heating, they tend to "walk" on the slippery surface, so you may have to nudge the stove back into position once or twice a year. The foot style makes a difference. The ball tends to slide easily, I put a small patch of felt on the bottom of Bear Feet, I suppose a small rubber pad under the foot would prevent movement too. Any stove does this and pedestals not bolted down slide the easiest just loading them. They have the least amount of downward pressure per square inch of contact.

 

[Todd67]

That would be fine too. A stove board that is UL approved is the simplest solution under the stove.
https://www.amazon.com/dp/B0062MAQ5E/?tag=hearthamazon-20

They work good for wall protection too. Not too heavy. My Kitchen Queen required a bit more protection than the single layer under my tile so I sat the cookstove on the largest one available. I find as a stove expands and contracts with heating, they tend to "walk" on the slippery surface, so you may have to nudge the stove back into position once or twice a year. The foot style makes a difference. The ball tends to slide easily, I put a small patch of felt on the bottom of Bear Feet, I suppose a small rubber pad under the foot would prevent movement too. Any stove does this and pedestals not bolted down slide the easiest just loading them. They have the least amount of downward pressure per square inch of contact.

I never thought about the stove "walking" across the floor like that, but it makes sense. We bought our cement board at Lowes or Home Depot. Next time I install a stove I'll check out these boards on Amazon. I might use it on the back wall when I install the Grandpa Bear in my garage this summer.

 

[coaly]

Ace Hardware stocks them. Not all sizes and colors, but you can see them there.

 

[harbinger50]

Lots of good info. So using materials on hand... namely my tiles, I could do the shield for the floor and the ones for the walls? Would a tile/cement board shield an inch away underneath like your metal shield work too?

I would have thought cement board and tile would be too flimsy to mount upright... unless I had a lot of mount points... hmmm. Lots to think about that's for sure. I guess I would mount the cement boards to the wall first then do the tile on them? I'll have to check, I think my tile size was too large for vertical installations. I'll have to check on that.

Thanks for all the help and info. Gonna mull all this over.

 

[coaly]

You set a couple bricks on the floor, against wall to raise the cement board panel and support the weight.

Fasteners to the wall should have insulated spacers (like those used with electric fencing) and cannot be located down the center line of the stove. There is no downward pressure on wall spacers. This creates a shield that cool air enters at the bottom and rises behind it carrying away the heat. The shield size must be the size to prevent any measurement from the stove to wall on any angle being within 36 inches to the wall. See diagrams below. The stove to wall clearance can be down to 12 inches to wall, not shield. Covering of cement board is only for looks and not required for safety. Cement board could even be painted. Size of tile on walls does not matter as long as you use the correct mixture and product with good adhesion properties. Many times wall tile needs to be taped in place until the mortar bed dries.

No, you can't use cement board as a shield 1 inch from stove bottom. Like cement, It can't support its own weight. This is a metal shield like a heat shield under a vehicle protecting floor or fuel tank from the heat of exhaust or a catalytic convertor. Same principal. Air is the best insulator. To prove my point, if you keep your finger very close to a hot pan on a stove, you will not burn your finger as close as 1/4 inch or even 1/8 inch away. This is due to the insulating air between your finger and hot surface. 1/8 inch of air space is as good as 1 inch. Touch it without air space and you get an instant burn.

The stove board simply sets on the floor without damaging tile or needing to make a permanent hearth pad. $40 and you're ready for the stove.

You should not lay cement board on top of the existing tile, installing another finish over it. It needs to be set in a bed of mortar such as thin set just like cement board is installed on subfloor for even support without cracking (grout between tiles will crack, or even crack tiles if not supported in a mortar bed). It is going to be extremely difficult screwing it down through existing very hard tile. You would need to hit the grout joints with screws and use a diamond bit near the edges where it needs to be screwed through tile.The thin set and diamond drills you go through are going to be more than $40 plus many hours of labor. This floor protector becomes permanent.

 

[harbinger50]

Coaly, what thickness is that shelf metal you put under your stove?

 

[coaly]

Mine was 20 ga. but it needs to be 24 ga. minimum. (Connector pipe thickness)

I used 20 gauge because there was a drawing revision sent to fabricators in 1977 with specifications for adding a bottom shield, making the original model I a II. The drawing called for 20 gauge cold rolled steel bolted on. So I built one to factory specs. but didn't bolt it on since this stove is a factory painted Bark Brown Mama Bear. Rare, and the only other optional color back then.

This was before UL testing became the standard, so it was tested, but not to UL testing standards.

 

[harbinger50]

Mine was 20 ga. but it needs to be 24 ga. minimum. (Connector pipe thickness)

I used 20 gauge because there was a drawing revision sent to fabricators in 1977 with specifications for adding a bottom shield, making the original model I a II. The drawing called for 20 gauge cold rolled steel bolted on. So I built one to factory specs. but didn't bolt it on since this stove is a factory painted Bark Brown Mama Bear. Rare, and the only other optional color back then.

This was before UL testing became the standard, so it was tested, but not to UL testing standards.

Cool. I saw some 16 at lowes. 24 x 24

 

[harbinger50]

Wait, so why couldn't you do the same sort of shielding on the back and/or sides of the stove? Basically just building a shield shell around it without making all these changes to the house. Just asking.

 

[Piney]

Cement board is your friend. There are easy to follow rules on how to build wall shields using cement board - fastening, spacing, air gaps under and behind etc. Cement board on the floor is good too.
Read this:
https://woodheat.org/clearances.html