Pizza Oven Hearth (Fireplace Part VI)

We used firebrick to build the hearth of the wood fired pizza oven. First, we spread Heat Stop refractory cement (fireclay) to the base using a 1/4" notch trowel and then we placed the firebricks bricks on the cement as tight as we could. Three times, we pulled a brick back up and removed or added cement to the bottom of it in order to get them all to lay flat. A brick that's too high or too low could keep the peel from sliding easily into the oven. A book called "The Bread Builders," recommends omitting the mortar between the bricks (I followed their advice) because it could wear off into your food, and because it will make your life simpler if you ever endeavored to replace a brick in the hearth.

It wasn't necessary to cut/break the bricks precisely at the edge of the hearth, because these edge bricks get covered by the sides of the pizza oven. In the back of the hearth, we left a blank spot for the ash dump (this hole could serve as fresh-air makeup if needed).

Immediately after finishing the firebrick hearth, we started cementing the brick oven segments into place on the hearth. The kit contains 5 oven segments and the entrance tunnel, so each piece makes up 60 degrees of the 360 degree circle that forms the pizza oven. Jockeying the cast ceramic pieces around to obtain the best fit (while maintaining the thinnest mortar joints possible) was not trivial, so I was glad to have the stone mason there to help. These are large heavy pieces that have been molded wet and then presumably fired in a kiln, so the tolerances are a little loose. When we finally got most of the joints to be 1/4" or smaller, I decided that the bread and pizzas weren't going to care how big the joints were. We let the assembly setup over night and the next day I came back and placed the dome on top. I left the joints on the outside of the segments sloppy, but because the cook (my wife hopefully!) will be able to see the joints on the inside of the oven, I used a wet sponge to clean them up (just as you would when grouting floor tile). For the joints in the back of the oven, it was necessary to nail a sponge to a long stick!

After the whole thing was assembled, I started troweling on "insulating castable refractory" purchased with the pizza oven kit. Two 35 pound bags provided a little les than 1" of coverage to the surface of the oven. I found it hard to get more than an inch of wet refractory to stay on the sides of the pizza oven, so I waited a day before applying the second coat (another two bags). The first coat was rough and had cracked a little, so the second coat stuck much easier. This last picture shows the pizza oven covered with the insulating refractory next to the Rumford. I just finished cutting the stones for the arch above the Rumford. I cut the keystone for this arch and the stones in the smaller arch from the same very large piece of rock.

If you're interested, the maker of the pizza oven kit and the rumford kit, has started a page on his company's web site to track the building process of our pizza oven and Rumford fireplace. The pictures on his site and my blog are redundant, but he includes email correspondence that I've had with him (my questions and his answers) on his web site. I have found him to be very responsive to my questions. Here's the site: http://www.rumford.com/oven/Massie.html