Monday, December 31, 2007

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:


Blogger Tyson said...

That is going to be the most magnificant centerpiece of any home on the planet!

Excellent job!


January 10, 2008 at 6:14 AM  
Blogger oldmilwaukee said...

Thanks Tyson! It is taking forever to fit these stones together in a dry stack fashion. Once we get 9 feet up (to the 2nd floor), we'll probably switch to concrete block covered in stucco, then go back to stone when the chimney leaves the roof. How is your outdoor Rumford going?

January 12, 2008 at 5:31 PM  
Blogger Mike Lloyd said...

I just discovered your blog when I was researching Rumford Fireplaces. We are looking to build a home, and I was facinated with your building project. I spent a lot of time reading your posts.
Anyway, I would love to know the demensions of your fireplace/pizza oven/stove alcove. It is an impressive set-up. Also, when you built up the slab on the main level, did you fill in the space inside the block walls in the basement?
Thanks for your time.

January 4, 2010 at 3:36 PM  
Blogger Thomas Massie said...


Glad you enjoy the blog, and good luck with your own projects! Here are some answers to your questions:

9'10" x 5'4" contains the whole stone structure which has the fireplace, firewood storage, pizza oven, cookwood storage, cookstove alcove, and a bookshelf. If I were to do it over, I would make it at least 11' x 6' and life would be a whole lot easier. 12x7 would really make life easy. Oh well, I didn't waste any space, but I did have to scratch my head a lot.

In the basement, the structure is shaped like an H with the heavily reinforced slab poured on top of it. The poured walls (not block) of the H shape are 18" thick and 10" thick. (18" thick where the weight of the 36' foot chimney is concentrated) So to answer your question, I did not pour it solid. In fact, my wood boiler fits nicely inside of one of the empty sides of the H. Check out the picture url below... imagine my boiler sitting right behind the dude messing with the pex insulation. The exhaust for my boiler goes through the window looking opening in the middle of the H. When we poured the H, everyone asked me while I was blocked out the window like opening. It came it handy, because the flue for the boiler is on the other side of the H.


January 4, 2010 at 9:18 PM  
Blogger Thomas Massie said...

BTW, now that we're living in the house, the pizza oven is one of the most awesome features we included in the house. We use it quite often. In fact, we went and helped a friend build one in his backyard... from scratch. If building inside, I would recommend the kit. If building in the backyard, you might build it from scratch, but you can't go wrong with the kit. We are so glad we did it.

January 4, 2010 at 9:22 PM  

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