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Wood fired oven - housed in dry stone structure

33K views 190 replies 24 participants last post by  drystoneoven 
#1 ·
I'm in the process of building a wood fired oven within a dry-stone structure. I've been at this at least since September 2010, when I started brainstorming. Since I started so long ago, I have already come quite far, and am currently working on the oven itself. You may notice that I'm not a professional mason in the sense that I don't make my money doing this. I'm actually an attorney, but I take stone work very seriously. I hope no one will hold that against me!

That said, I started out doing dry stone masonry in 2008. I've done quite a few free standing walls and retaining walls, including some corners, steps, an arch, etc... However my wife wasn't very impressed, considering the time I was spending outside. So I set off to build a brick oven housed in a dry stone structure, meaning there would be no mortar to set the stones in. I realized that in order to do this, I would invariably have to find a gigantic capstone to cap everything together at the end, or the oven would get wet and I wouldn't get all the stones tied together properly. So I went in search of a stone that might work, so that I could design an oven and structure underneath it. I found one on a creek bank which was already almost rectangular. After I split a section off, it was 6'x4'x9" thick, and more importantly, it was accessible by the creek in only 2 feet of water, meaning I could drive a tractor up the creek to get it. So that's what I did first. I built a sled to lay the rock on, went down to the creek and jacked it up and slid the sled underneath and towed it out of there. Here is an album of the pictures: http://imgur.com/a/bsS2O

Here are two pics of the stone, for those who don't wish to visit an outside site.



I may be a bit slow on updating, but that's only because I'll be uploading and arranging pics as I go. The next post will be about how I chose a spot in the yard and dug and set the foundation.
 
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#4 ·
Picking the spot, foundation

Once I had the stone, I realized that the oven I would have to build under it would need to be massive. So I picked a spot in the corner of the back yard. This would've been way too large for most places (and may end up looking too big at my house), but I live on a 2 and 1/2 acre lot on the front of a 300+ acre farm, so I'm not too worried about scale. I used a bobcat to dig stuff out and then staked out a foundation. Unlike probably everyone who has ever built a wood fired oven in modern times, I decided to make a dry stone foundation, in keeping with what the entire structure would be composed of. I used stone from a water line dig-out (we just got city water back in 2009). There were some big slabs which I drilled and split with wedges and shims. First I did the outsides of the foundation, and filled it in afterwards. I know some people are bound to say "hey you can't use dry stone for a foundation, that should be reinforced concrete!" But haters gonna hate. Here is the album: http://imgur.com/a/aRcLn


Here are some of the better pics:

 
#6 ·
Given your language and location is it accurate to say you have attended dry stone workshops at the DSC? Possibly gotten "certified"?

No reason that an oven couldnt be put on a dry stone footing as long as you are at the proper foot depth for your location. Otherwise the movement in the structure, along with the thermal cycling of the repeated firings, will greatly shorten the lifespan of the oven.
 
#7 ·
@stonecutter

I'm not DSC certified, but I have attended a workshop. I haven't bothered to do the certification. I've won the Novice and amateur competitions at their walling competition and I've competed at the professional level (but did not place LOL!). Also, I'm on the board of directors of the DSC.
 
#8 · (Edited)
Building the base - learning patience

As you can see from the foundation, the oven was destined for an epic large footprint. I think the foundation measures something like 8'x9'. Anyway, I laid the foundation in November, 2010, and waited until spring of 2011 to get started on anything else. For the base, I was using mostly large stones that I had salvaged from old buildings that were torn down in the Bluegrass. Some of you might know that Central Kentucky has a great supply of limestone, and old buildings who had stone foundations are always being torn down. I was able to locate a few different people selling such stone for next to nothing, and little by little, rock by rock, I'd haul it over to my place. I needed to use large foundation stones for the whole thing, especially the quoins, because without mortar, each rock needed to secure itself by weight, so I could be satisfied that this thing wouldn't topple down. Anyway, I'm going to post the building of the base in a couple posts, because it seriously almost took me a year to do. This is my last post before going to get some lunch!

Here is the first album: http://imgur.com/a/6PrKT

And a pic from the album:
 
#9 ·
@Inner10

It freezes, but there isn't the sort of frost heave that you'd see in the northern states. I spoke to a master mason (both DSC and DSWA certified) and he said since I had dug down at least a foot I should be good to put my foundation in stone. If I mess it up I'm not worried, I don't even own the place where I'm building this thing!
 
#11 ·
Arch work for wood storage and ash trap

So you'll notice in the first pics building the base that I have a form in there for an arch. I put it in there because I needed a place for wood storage, even if small, and a way to do an ash trap. Plus, an arch always looks good and doesn't detract structurally as long as it's solidly built and buttressed.

In order to avoid front pinning in the arch, I used a gas cutoff saw that I got at a pawn shop for $100 to cut ribbons on the pieces, and then I chiseled them flat. This allowed me to work on the rock without hammering on it all day. There is nothing worse than working on a piece of rock for 15-20 minutes only to have it break altogether by too much chiseling and hammering.

In cutting out and placing the voussoirs, you'll see I was not completely uniform in the size or angle of the voussoirs. Perhaps on the stone arch for the oven I'll be ready to get it perfect...

You'll see some dogs in the arch form if you look at the album. Somebody abandoned them on our road. They were starving and came to hang out in the arch form.

Here is the album link: http://imgur.com/a/ZkvfV

A few pics:



 
#13 ·
Finishing the Arch

Around August, 2011, my pawn shop stihl cutoff saw stopped working, and I lacked the political capital with my wife to buy a brand new one. So I waited and waited to have it fixed, to no avail. So three months later, in November, I rented a saw and finished within a few hours. The keystone is another salvage stone from an old post office in Lawrenceburg, Kentucky, which was built heard tell in 1906 or thereabouts. Anyway, I bought it off the contractor who demolished the building, along with some brick which we'll see later. You can't see it, but I actually made the keystones two deep, so the arch is something like 2 feet or more deep. In between the two keystones is a spot for an ash trap!

Here is the album: http://imgur.com/a/IKBGD

And a few pics:



 
#15 ·
Finishing the Base of the Oven

Once I was done with the arch, I was set to build the rest of the base. The problem was that it was November already, and it's tough to build this sort of stuff in the cold. However, the winter of 2012 has been extremely mild, and I succeeded in finishing the base of the oven sometime in January I believe. As you can see from the last picture, I was ready to pour a slab so I could even things out. This is the only section that is not dry stone, except for the oven itself of course. I guess if I wanted to remain pure stone, I could've got a huge cut slab of indiana limestone and laid my firebrick hearth on there, but sounds like it would just break from the heat, not to mention being terribly heavy to install.

Album here: http://imgur.com/a/Lv23j

Selected pics:



 
#16 ·
The oven, part I

So time to get up to date where I'm at now. Once I had the base prepared in mid January, I knew I would have to wait until spring to pour because of how cold it would be. But then a warm January day came and I took off an afternoon to mix and pour some 16 bags of high strength concrete. I didn't put any vermiculite in, which I imagine people will tell is bad. Well it's done now, so, oh well. And of course I didn't get it quite level. My babysitter had to go and it started to rain unexpectedly. So I ended up covering it up when it wasn't properly finished.

After that I built one more level stone which was to be as deep into the oven as possible. Then I cut the slab down the middle to allow for expansion and smeared on a layer of heat stop mortar, the kind that is $56 per 50 lb bag. With damn near 3/4" of that stuff everywhere to level things up, I laid the fire brick hearth (but not before I placed a thermocouple sensor in the middle of the oven!). After that dried, I laid the first level of the brick oven with heat resistant mortar, to level things up perfectly. Then I laid the brick work for the ash trap, which you see below. Then I laid two more levels of brick on there and formed it up so as to pour insulating concrete on the outside of the brick, to the tune of 3.5". I poured up above the brick walls on the sides so as to give a buttress to the springer bricks I will be using in the brick vault of the oven. It'll be the weekend of March 17 before I can possibly get the vault done, so I'm in a holding pattern right now. I've been planting greens in my garden!

The album: http://imgur.com/a/EebYm

Some pics:







 
#17 ·
You will regret the lack of insulation under your hearth, and I would suggest that you tear out what you have so far and install 3-4" of perlcrete under the hearth. It also looks like you are following the Allen Scott plans which is not an optimal design unless you are planning on producing commercial quantities of bread or have an unlimited source of free wood.
 
#18 · (Edited)
Maybe you would tear it out, but not me. I think it'll be okay without the extra insulation below, even though not optimal. I do realize that makes the hearth a bit harder (and longer) to heat , I'll just have to use more wood I reckon.

I am not building to Alan Scott's design, rather I'm following Rado Hand's design. And funny you should mention it, I do have unlimited access to free firewood! I live on a large farm where a tree somewhere is constantly falling and in need of being cut up and burned.
 
#23 ·
It looks like it has 2 saw cut edges. A big NO NO in my book. The shape makes it stand out the most. you never see crisp edges on a triangular stone. They would have rounded points and edges. If a saw cut edge is used on my work the edge will always be dresses with a chisel.
 
#24 · (Edited)
You never see those edges on a natural stone huh? I picked that stone because it was naturally completely flat on top. I cut the bottom but that was it. I floated that stone out of a creek in a canoe. It has beautiful crystallization such that I saved it for that exact spot. I'll take a close up pic later and you'll see what I mean. I do understand your concern with roughing up the edges. I think when it's all done, it will fit in splendidly, even without roughing the edges.
 
#30 ·
I had thought that I didn't need further insulation under the hearth , and thus didn't plan for the extra space. By the time I had considered doing it, the slab was poured and the hearth was already set to be 47-48" high, so I didnt want to make it any higher. I probably should've further insulated but I think it will be okay. (in other words it'll have to be okay!)

As to the side insulation, I still have time/room to apply some amount of insulation outside what I've got on the walls and of course on the vault of the oven. Reccomendations as to the proper mixture?
 
#31 ·
Rado is an enthusiastic guy, but his oven design is not much better than the AS oven. Both have too much mass and not enough insulation.

If you are building a commercial oven for daily use the mass both include is a good thing, although both designs are under insulated.

The idea is a discrete thermal mass, isolated and insulated to a high degree. For normal occasional use, 2-3" of mass is more than adequate, and even for bulk breadmaking 4 inches is sufficient.
 
#32 ·
I had thought that I didn't need further insulation under the hearth , and thus didn't plan for the extra space. By the time I had considered doing it, the slab was poured and the hearth was already set to be 47-48" high, so I didnt want to make it any higher. I probably should've further insulated but I think it will be okay. (in other words it'll have to be okay!)

As to the side insulation, I still have time/room to apply some amount of insulation outside what I've got on the walls and of course on the vault of the oven. Reccomendations as to the proper mixture?
 
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