Engineering Bricks for the Arch?

[cleverdick]

OK next question...

On the Ephrem 2061 which I shall be using, the top of the arch forms the front of the vent. The chimney will sit on that, with some kind of thermal gasket. Therefore, I am undecided as to whether to use dense firebricks or engineering bricks for the arch. Either way I am planning to incorporate a 10mm thermal break between the arch and oven body, packed out with stove rope. The front wall of the enclosure will be built around the arch, and therefore I don't want it to get too hot, since it will be tiled. I would prefer the appearance of smooth engineering bricks for the arch, with matching bullnose bricks for the landing. The thing is, will they take the heat?
I've thought about a short firebrick arch, with a full-depth engineering brick arch in front of that, each with its own thermal break, but this is where the design gets out of hand. Any clues?

[mklingles]

I think your thinking to hard. I have no thermal break. Firebrick dome connected to firebrick flue chamber. My chamber is 1 full firebrick (~9") from inner arch to outer arch. The outer arch is ~4" think stone.

At full burn you can touch the outer arch and it's hardly hot. I think the hottest I measured the outside of the chimney vent firebrick was about 95deg F.

So unless I'm missing something there's an inner arch fire brick - some distance to allow the flue then an outer arch. I don't see why the outer arch can't be engineering brick. Especially if you have afire break.

[dmun]

Your entry gets hot. That said, any sort of brick should work. We've seen common brick entries in front of firebrick domes. Engineering brick is a UK term: I think it means a higher fired (harder and denser) red clay brick. Should work fine. The only material to worry about in this application is portland based concrete.

[david s]

I think it is the expansion of the inner oven creating pressure on the arch which is the greater problem, rather than the materials ability to withstand the heat. I still feel that a thermal gap filled with 6:1 vermicrete is a good solution.

[DaveW]

I thought of that plus, I didn't trust my firebrick arch so I supported the chimney with Steel Lintels. The clay flue sits on the brick. The mistake I made was mortaring in the flue which I think caused it to crack (sounded like a fire cracker when it went).

I also left a gap between the decorative arch and the inner firebrick.

Dave