A modernist Casa 90 build

[Razor]

I'm just putting the final touches on a year long Casa 90 build and thought I'd share photos of the build and the build process. I'll start with some of the finish photos, and then post the progress from start to finish. As you'll see, I ended up doing a pretty non-conventional take on a WFO design.

[admin]

Fantastic oven! Can't wait to see the build pictures!

[Gulf]

"Modernist" is cool! Very clean, "stealth like" lines on the oven. I'm also looking forward to the build pics. Especially,the door .

[Razor]

Funny you should call it "Stealth like" Gulf, my nickname for it is the "stealth fighter". We have a small back yard, so a lot of the angled sides are there to help reduce the perceived visual size of the oven.

OK, so here's the back story. Several years ago, we were considering building a WFO in our back yard. We live amongst tight lots in the central part of Ottawa, Canada. I already had a copy of Alan Scott's "The Bread Builders", lurked and researched builds on this forum, and knew the type I wanted to build. One night while researching and comparing oven kit manufacturers, Google popped up a Kijiji ad for someone in town selling a brand new FB Casa 90. It turned out to be a well known restaurateur in town who was renovating his home kitchen. After having the oven assembled and ready for the refractory mortar pour to seal everything in place, the building inspector wouldn't approve it because it didn't have a CSA approval stamp for indoor use. So, he had to unload it and get another model, which is how I got to inherit the kit. You can read his account in our local city magazine:

http://ottawamagazine.com/homes/focu...ayful-palette/
"And then the conversation turns to the wood-fired oven. ?Now that was the real saga,? says Beckta, shaking his head. The couple were inspired by a Maine vacation a few years ago, when their rental cabin was equipped with a wood-fired oven. After cooking in it every night, they knew that any future kitchen renovation would include just such an oven as a central element. ?Humans are hard-wired to love stuff cooked over wood,? Beckta explains. ?When you taste food cooked using this method, you remember it.?

What they didn?t realize was how much of a hassle the decision would turn out to be. When the first oven, imported from the United States, arrived, they discovered it was not approved for use indoors in Canada. (The couple sold it on Kijiji to someone who plans to set it up in their backyard.) "

Since they already assembled the chimney, I just had to grind off the high heat adhesive that was used to seal (see photo below) and it was pretty well as good as new.

[Razor]

The oven then sat on a skid in our back yard, tarped over for two years while we planned on getting an exterior reno done on the back of our house. Once that reno project began and the deck was torn out and demolition done, I used some tar paper to template out where on the lot to place it. I decided to drop it where a walkway divides our vegetable garden. This lets us look straight out our kitchen's rear door, directly at the oven, so we can monitor it from inside on cold winter days.

[Razor]

After excavating and infilling with crush stone, I poured the slab. I didn't get any photos of the form or the pour. The one thing I did know is I didn't want it to be a big box, so formed a half-circle shape to the back of the oven. I formed this with hardboard bent to shape with mold release on it.

I also knew I was planning on cladding the house with a dark cement panel board as part of the reno, so I dyed the front of the slab a dark charcoal. The dark area of the slab sits above 3/4" higher than the rest of the slab to come flush with decking that will surround the oven later.

You can see in the photos below, I've scribed in the outline for the cinder block stand. Since the back is rounded, I opted for a tapered H-shaped pattern. The H pattern will play a roll in the storage system for the oven later on.

[Razor]

Next up was dry-stacking the cinder block base to support the hearth and dome. After everything was plumb and straight, I filled every other void in the blocks with concrete to lock it all in place. Vertical rebar in the 4 corner blocks. Once the blocks set, I made a temporary support in the open areas of the stand to support a sheet of concrete board (Durock) to build the hearth form on top of.

The second and third photo below show the form for the concrete hearth with rebar in place, mid-way through pouring the structural layer of concrete. You can see in the photos, I left the top 2" of the form unfilled. This would be topped with 2" of vermicrete for some added insulation.

The last photo gives a decent view of the curved back for the hearth. I used hardboard, with a mold release, held to shape with foam board backers. The curve is to match the curve on the bottom slab.

[Razor]

While the structural concrete part of the hearth was still wet, I mixed up a batch of vermicrete (vermiculite and portland cement) and laid that down over the structural layer. As you can see in the first photo, it got dark pretty quick. After covering with plastic, I let it cure for a few weeks and removed the form.

The second photo shows the front of the hearth. You can see I cast two anchor bolts and a steel lintel into the hearth. This is to allow me to mount a landing/mantle afterwards.

[Razor]

I just like this photo. It shows the bonded layers of structural concrete and the vermicrete on top.

[Razor]

When I set the cinder block for the stand, I ran a cross section of block to tie together the left and right walls (like the horizontal line in the letter H). I left out the top row of blocks in this section. After the hearth went in above it, it creates an opening between a front storage area and a rear storage area. This will allow me to have a long oven tool storage area, where I can slide my peels and oven brush horizontally through this gap. You can see the opening below.

[Razor]

The next step was to lay down the FB rigid insulation board. Since I bought the oven kit "used" the board was already pre-cut to shape. After that it was just a matter of placing the fire brick floor, assembling the dome and sealing it all with refractory mortar. As it was getting into late fall at this point, I ran an extension cord into the oven with a lamp on and blankets on the dome to keep it warm enough to cure properly.

[Razor]

When I bought the kit from the previous owner, it came with two chimneys: a single and insulated double wall one. After attaching the mounting plate, I used the single wall one to figure out some of the framing. This is when I ran into my first real issue. When I went to attach the double walled chimney, it didn't fit to the chimney anchor and there was no second anchor included. I had to remove the one I had just attached, and order one that would fit the insulated chimney. The proper mount is shown in the second photo.

After that was all in place I started framing with steel studs. At first I had the front face of the oven flat, so the plan view looked like an inverted U. This made it look pretty massive in the yard, so I started adjusting the framing, pulling the front-top corners and forward at the top. This helped not only make it look smaller, it will create a small overhang above the oven opening to keep rain out. Photo below is the rough framing after adding in the angles.

[Razor]

After wrapping several layers of FB insulation blanket, I finished filling in the framing, especially a lot of studs around the back curve since I would be bending cement board to shape and it would need plenty of screw in points to keep the tension from pulling out the board.

For the curve, I snipped the outer face edge of standard steel track in 2" intervals, bent it to the curve and screwed a band of sheet metal to restore rigidity to the track.

[Razor]

I don't have any good photos of the oven with the cement board sheathing over the framing. Basically at this stage I covered the upper oven in Durock to create the main "fire box". All seams where mortared. After the sides were done and I had, essentially, and open topped box, I filled the cavity to the top with vermiculite (I was going for over the top insulation). One that settled, I capped the top with more cement board and could start the first fire.

[Razor]

We had an fire inspection engineer from the local fire department come buy to approve the oven on the first firing: just a few sticks and paper. During the curing stage we managed to roast a few dinners in it. After fully curing, one of the first things we made in it was a porchetta for Christmas last year.

We used the oven as was - just with the rough cement board sheathing -- through winter and continued finishing in the spring.