# Insulating the bottom of woodstove



## Ogeechee (Jan 15, 2014)

I have seen some older wood stoves that had a hard substance that was cream color like fire bricks poured in the bottom of wood stoves to insulate the wood stove. What was it and how effective was it compared to fire brick. These stoves had regular fire brick around the sides.

I have an older Jotul 118 but someone placed a 1/2 inch plate piece on the bottom and welded 1/2 inch plate going up both of the sides about 1/2 way up. I think they did this rather than purchase new side burn plates. Until I can get the welds cut I do not know if the floor burn plate is there. I was thinking of removing the 1/2 inch plate and lining the bottom sides and back with fire brick. Would I need to line it up to the top inner baffle plate separating the top from bottom chamber? Second question: Would this adversely affect the heating and efficiency of the stove? If the bottom burn plate is in place I could replace the side burn plates or lins the sides and back with fire brick. Again the question would be how high up the side would I have to line the sides and back? I appreciate your responses.


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## mellow (Jan 15, 2014)

What you saw was refractory mortar,  you find find more info about it here:   http://www.heatstoprefractorymortar.com/premixed.html


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## begreen (Jan 18, 2014)

Firebrick on each side is going to reduce the width of that narrow firebox by a couple inches. And it will need some sort of retainer added. Did they do a good job with the steel liner? If so, I would try burning with the steel left in place for a season.


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## snydley (Jan 18, 2014)

I have a Vermont Castings Resolute III, (double doors with windows). When I got it 6 yrs. ago I bought some firebrick, and with a tile saw I cut the bricks so they would fit tightly in the bottom of the stove. Works great for me. I don't know if it was necessary, but it keeps some of the heat off the hearth.


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## Earth Stove (Jan 18, 2014)

Ogeechee said:


> I have seen some older wood stoves that had a hard substance that was cream color like fire bricks poured in the bottom of wood stoves to insulate the wood stove. What was it and how effective was it compared to fire brick. These stoves had regular fire brick around the sides.
> 
> I have an older Jotul 118 but someone placed a 1/2 inch plate piece on the bottom and welded 1/2 inch plate going up both of the sides about 1/2 way up. I think they did this rather than purchase new side burn plates. Until I can get the welds cut I do not know if the floor burn plate is there. I was thinking of removing the 1/2 inch plate and lining the bottom sides and back with fire brick. Would I need to line it up to the top inner baffle plate separating the top from bottom chamber? Second question: Would this adversely affect the heating and efficiency of the stove? If the bottom burn plate is in place I could replace the side burn plates or lins the sides and back with fire brick. Again the question would be how high up the side would I have to line the sides and back? I appreciate your responses.


My 1986 Earth Stove came lined with firebricks covering the whole bottom and factory arranged to use whole sized bricks leaving/allowing the cast grate in center to fit snugly. I put in two mild steel bar stock 1" thick X 12"+ long to serve as a low profile wood rest/grate allowing air to get under the wood and it works great!! I have zero damage to any of the floor bricks. The bars run perpendicular to front glass loading door. And I've used this stove a lot for several yrs.


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## Boil&Toil (Jan 19, 2014)

Ogeechee said:


> I have seen some older wood stoves that had a hard substance that was cream color like fire bricks poured in the bottom of wood stoves to insulate the wood stove. What was it and how effective was it compared to fire brick. These stoves had regular fire brick around the sides.
> 
> I have an older Jotul 118 but someone placed a 1/2 inch plate piece on the bottom and welded 1/2 inch plate going up both of the sides about 1/2 way up. I think they did this rather than purchase new side burn plates.



Castable refractory. You can find it at ceramics suppliers, among other places. Firebrick is often (not always) cheaper.

Awww- a 118 - our first "modern" woodstove.

I'd agree with Begreen that you might want to give the modification a try - lord knows the original burn plates warp & crack enough to make me think they are a bad design, unless you happen to be the guy selling replacement burn plates.

If that doesn't work out, and you go with refractory - for the sides, you might borrow a trick from Marc Caluwe (passion for fire and water) and use silicon carbide refractory - available at ceramics suppliers as fuel kiln shelf material (electrically conductive, so not often used in electric kilns) - it's is refractory but it's not a high-insulation value refractory. Ideally you'd find kiln shelves that were the right size as ordered.


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## begreen (Jan 20, 2014)

I'm ok with sacrificial burn plates. They last a long time and protect the outer shell well. We got about 20 yrs out of them in our 602. Replaced them and the baffle and the stove was like new again.


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