I'm planning on a single-bell batch-box masonry heater this summer, and the current front-runner design is a tall fieldstone rectangle.
But I got to thinking, "You know what would be a way to trade some money for time and achieve an almost-guaranteed beautiful level of fit and finish? A tall box built of four stone slabs and a small one on top. Who sells stone slabs? Monument companies."
So I called my local monument company. I talked to a real helpful guy about what I was after, and here's what I learned:
1. Monument companies generally buy slabs from quarries and engrave them in-house. They're not sawing or grinding anything after it arrives; they order the faces and edges the way they want them.
2. A 60" x 36" x 4" slab costs around $800. Freight from Georgia to Michigan is around $700. So my box would carry a price tag of about $3900 plus some miscs.
3. That slab would weigh a little over 1,000 lbs, so four of them plus a cap would get you over two tons handily. (Would also require equipment to erect.)
4. He knew about limestone and granite, but had never dealt with soapstone.
So. That's an itty-bitty piece of knowledge, but it was useful for me, so maybe it will be useful for you too.
Mike Cantrell wrote:It did occur to me to go out back of the store and see if they had a pile of rejects or mistakes. But I don't know if I'd want somebody's name and dates showing in my living room.
Mike, you made me think. In france, often after thirty years or sixty, they do "lifting of the bones" which means getting the bones out of a grave, to get some room for the new deads. Sometimes, if the familly has moved, or doesn't wich to keep the concession for the land, it is allotted to somebody else. I wonder what they do with the old stones.
Sorry I am late to the conversation. I would strongly suggest that one must be very careful with large stone slabs unless very familiar with the art of splitting, shaping and carving stone. Most species do not deal well with "differential heat extremes" over a given time...especially if not well backed, and even then there are often issues. Only a very few stone species...most notably in the steatite (aka soapstone)...work well.
Jay C. White Cloud wrote: I would strongly suggest that one must be very careful with large stone slabs unless very familiar with the art of splitting, shaping and carving stone. Most species do not deal well with "differential heat extremes" over a given time...especially if not well backed, and even then there are often issues. Only a very few stone species...most notably in the steatite (aka soapstone)...work well.
Thanks, Jay! The problem of cracking the slabs certainly occurred to me. I'd have gotten around to asking about it specifically, if I hadn't ruled this out on account of the cost.
So would you trust a soapstone slab of the same dimensions (60"x36"x4") to resist cracking if used as the bell of a masonry stove? How about if it were 8" thick?
Soapstone wood stoves and some masonry heaters of the same material are often as thin as 30 mm for certain areas. I would trust 50 mm if I selected the stone in the quarry myself, yet would prefer 100 mm as my minimum just because of mass and performance balance in the system. I may incorporate a few areas in the 50 mm range for faster heat up and perhaps cooking. Thetford Quebec has one of the largest and still operating steatite quarries here in North America, with the rest coming (unfortunately) from China and Brazil. A square, octagonal, or other shaped bell would work fine in my view. It is a matter of skill set in shaping and method of jointing the slades that will give the most challenge. If (or when) I would do another RM masonry heater, it will be built of soapstone with similar design parameters to what you are suggesting. I would have to see an actual CAD or elevation cross sectional schematic of your design to go into more detailed evaluation. Note, most other stone species (not all) could not take the constant thermal differential without spalding and failures.
Permaculture isn't that hard to understand. Sometimes a little bump helps: richsoil.com/cards