First course on or around cooking surface?

[Neal]

It's apparent that if you want to place your first course of firebrick around the cooking surface rather than on it, there is a lot of cutting of both the FB board and cooking surface firebrick in order to get a nice round base for the dome. If the completed oven is going to be enclosed, is there any advantage/disadvantage to placing the first course of firebrick on the cooking surface rather than around it?

Also, can someone link me to a thread that might offer a definitive approach to cutting the dome firebricks on both the vertical and horizontal planes in order to get a nice tight fit. I have seen pictures of Les' build, which is beautiful, but can't find a thread where he discussed how he determined his cuts. Unfortunately I don't have a CAD program.

Thanks in advance.

Neal

[dmun]

Re: First course on or around cooking surface?

Floor inside wall advantage: hypothetical ability to replace floor if it wears out. This is a rare occurrence in home ovens that aren't fired every day.

Dome built on floor advantage: it's easier, less cutting is required, and at least theoretically the mass of the dome is more widely spread over the insulation.

The verdict: Do it either way, both ways work fine.

Cutting every brick on three faces to get a perfect fit dome is a big, big job. A CAD program can help, but you can lay out the cuts with a straight edge and a string. As far as shop drawings of each cut, well it's not something I've seen.

I recently saw a slide show of one of the big name Italian pros building the oven at Donatella in NYC. They just trimmed each brick as they lay it up, so they fit on the inside, and mortared them up just like we do, but with no protruding mortar. Then when the dome was done, they put a parging coat on as a slurry, so it would fill any air spaces. I think if it's good enough for the famous makers, it's good enough for us.

[tusr18a]

Re: First course on or around cooking surface?

Google sketch up is a great free cad-like program. I found it a great way to work out problems before I actually started cutting the bricks. Like any software, it takes a little to get used to. With that said, I am not sure that I would have been able to figure this all out without the help of the software. I probably would have made so many costly mistakes that I would have stopped mid-stream. The old saying to measure twice and cut once is definitely true.

[Les]

Re: First course on or around cooking surface?

Neal,
Cutting the floor wasn't that hard. I laid the floor brick out and drew a circle. It will take a few passes on the saw but it was very easy to do. I did draw mine up on CAD so I had a template for the dome brick. As I built up, it required a lot of improvising. Many, many trips up the step stool to get the brick to fit. The hardest part was getting the shim height right for the angle on the sides. If you go this route, be prepared to take your time. Don't rush your build, enjoy it (I can say that now that it's done ).

Les...

[Neal]

Re: First course on or around cooking surface?

Thanks all for your thoughts. I watched the slide show that dmun linked and it looks as if this "old world" builder simply whacked the bricks in half and glued them up. I guess it is truly a case of function over form (but for the record Les, your work is much more attractive).

If I understand what Les did (and it's hard sometimes for me to picture things in three dimension), he made compound cuts in the sides of each brick such that they were wider on the outside of the dome than the inside, and when viewed from the inside they were narrower at the top than the bottom. Is that correct?

What dmun is saying is take the half brick (or third or quarter, whatever you are down to) and taper the sides (wider on the outside of the dome than on the inside) using a string affixed to the center of the cirlce to get the angles. Get a good tight joint on the horizontal plane and live with some mortar in the vertical joints. Again, I am picturing this correctly?

Thanks tusr18a for the Google Sketch lead. I am sure that I will resort to using it. If I am confused about cutting the bricks, I don't even want to begin thinking about the angle of each course. I can also see ending up with a whole pile of "test" bricks. At $2 each, I don't think so.

[Les]

Re: First course on or around cooking surface?

If I understand what Les did (and it's hard sometimes for me to picture things in three dimension), he made compound cuts in the sides of each brick such that they were wider on the outside of the dome than the inside, and when viewed from the inside they were narrower at the top than the bottom. Is that correct?

Correct. To keep the bricks off bond they need to get narrower as you go up. I recall that the brick would be only 5/8 of an inch at the top which is crazy hard to hold while you cut. So I changed the plans somewhere around course 10, 11, or 12.